LARGE SCALE IP ROUTING LECTURE BY SEBASTIAN GRAF

Size: px
Start display at page:

Download "LARGE SCALE IP ROUTING LECTURE BY SEBASTIAN GRAF"

Transcription

1 LARGE SCALE IP ROUTING LECTURE BY SEBASTIAN GRAF MODULE 3 BORDER GATEWAY PROTOCOL 1 by Xantaro

2 Interdomain Routing The Internet is a collection of autonomous systems An autonomous system (AS) is a collection of networks under a single technical administration An interior gateway protocol (IGP) is run inside an autonomous system resulting in optimal intra- AS routing either IS-IS or OSPF An exterior gateway protocol (EGP) is run between autonomous systems to enable routing policies, improve scalability and provide security BGP only choice today 2 by Xantaro

3 To use or not to use? Interdomain routing protocol is used when an AS is a transit AS when an AS is multi-homed to several internet service providers (using public AS numbers and provider-independent address space) when an AS is multi-homed to the same internet service provider for fault detection and traffic optimization (maybe using private AS numbers) when you need extensive filtering and manipulation possibilities that IGPs like OSPF and ISIS do not offer when your network needs to carry too much prefixes for an IGP When you are the administrator of a single-homed AS, think about static routing for simplicity 3 by Xantaro

4 In the Beginning... Three Napkins Protocol (TNP) Design by Yakov Rekhter and Kirk Lougheed during IETF-12 meeting in 1989 BGP-4 currently defined in RFC 4271 Ongoing discussion and development within IDR WG of IETF 4 by Xantaro

5 BGP Details BGP is an exterior gateway protocol or interdomain routing protocol used between routing domains (aka autonomous systems) BGP supports classless interdomain routing (CIDR) BGP is a path vector protocol using incremental updates BGP runs on top of TCP, port 179 BGP was built on a few fairly simple ideas: Provide loop-free routing by carrying information about the path the routing information traverses Minimize volume of routing information by using incremental updates Use TCP as reliable transport Encode information as collection of attributes using <type,length,value> style 5 by Xantaro

6 Autonomous System Numbers Autonomous System numbers identify a network within the public internet that is under a common administration AS numbers are attached to every Prefix routed in the Internet and are one of the most important BGP attributes AS numbers help to identify the origin of a prefix, as well as the transit networks to reach it Original a 16 bit value AS 1 to AS for public use in the Internet AS to AS for private use within autonomous systems like private (RFC1918), they should never appear in the Internet Today extended to 32 bit, as we ran out of 16 bit AS numbers Values up to RFC6996 also reserved a private range for 32 bit AS numbers AS to AS can be used similar as the range from to by Xantaro

7 Managing Autonomous System numbers AS numbers are registered to their operators like public IP addresses gwhois AS aut-num: AS as-name: XANTARO org: ORG-XHG1-RIPE import: from AS13237 accept ANY export: to AS13237 announce AS import: from AS20773 accept ANY export: to AS20773 announce AS admin-c: DUMY-RIPE tech-c: DUMY-RIPE remarks: For information on "status:" attribute read status: ASSIGNED mnt-by: RIPE-NCC-END-MNT mnt-by: MNT-XAN mnt-routes: MNT-XAN created: T16:07:01Z last-modified: T10:54:35Z source: RIPE remarks: **************************** remarks: * THIS OBJECT IS MODIFIED remarks: * Please note that all data that is generally regarded as personal remarks: * data has been removed from this object. remarks: * To view the original object, please query the RIPE Database at: remarks: * remarks: **************************** 7 by Xantaro

8 BGP Standards Selection of BGP standards (highly incomplete list): RFC 4271, A Border Gateway Protocol 4 (BGP-4) RFC 1997, BGP Communities Attribute RFC 2385, Protection of BGP Sessions via the TCP MD5 Signature Option RFC 2439, BGP Route Flap Damping RFC 2545, Use of BGP-4 Multiprotocol Extensions for IPv6 Inter-Domain Routing RFC 2796, BGP Route Reflection RFC 2858, Multiprotocol Extensions for BGP-4 RFC 2918, Route Refresh Capability for BGP-4 RFC 3065, Autonomous System Confederations for BGP RFC 3107, Carrying Label Information in BGP-4 RFC 3392, Capability Advertisement with BGP-4 RFC 4724, Graceful Restart Mechanism for BGP-4 RFC 6793, 4 bytes AS Number RFC 6811, BGP Prefix Origin Validation RFC 7454, BGP Operations and Security 8 by Xantaro

9 BGP Peering BGP exchanges routing information between two routers called peers or neighbors or BGP speakers BGP Session BGP session runs on top of a TCP session (port 179), i.e. BGP neighbors do not have to be directly connected to each other Normally, BGP neighbors require configuration explicitly External BGP (ebgp) session is running between routers in different autonomous systems. usually directly connected Internal BGP (ibgp) session is running between BGP neighbors within the same autonomous system. direct or indirectly connected 9 by Xantaro

10 BGP Finite State Model Idle Connect Active OpenSent OpenConfirmed Established 10 by Xantaro

11 BGP / IGP relation Typically you would use an IGP like ISIS or OSPF as well as ibgp inside your network use IGP to propagate internal prefixes like loopback addresses interface addresses IGP will find the most efficient path between two ibgp speakers use BGP to carry internet prefixes BGP next hops will point to addresses resolved by the IGP, hence a recursive lookup is used to construct the FIB ibgp sessions are usually set up between loopbacks as this increases stability do not go down as long as there is a working path between two routers can use load sharing for BGP prefixes, if multiple equal cost paths are available between two ibgp peers 11 by Xantaro

12 BGP / IGP relation Step 1 IGP convergence Before ibgp can operate the IGP needs to converge Afterwards R3 will know that /32 is reachable via R2 using next-hop R2 knows that it can reach /32 using it s directly connected interface using next-hop similar operations will happen on R1 and R2 for the other IP addresses IGP IGP Loopback /32 Loopback /32 Loopback /32 R / / / /30 R2 R3 12 by Xantaro

13 BGP / IGP relation Step 2 ibgp Session After IGP convergence R3 and R1 can establish an ibgp session Once the ibgp session is created, R1 sends a prefix towards R3 using it s loopback address as next-hop R3 will do a recursive routing lookup by checking it s routing table for the next-hop of than it will use the resolved next-hop ( ) for the prefix As traffic from R3 towards /24 will hit R2, it also needs to know the next hop R2 needs to have an ibgp session with R1 as well (not shown here) IGP IGP Loopback /32 Loopback /32 Loopback /32 R / / / /30 R2 ibgp Prefix /24 Next-Hop R3 13 by Xantaro

14 BGP Messages Overview Open (1) Update (2) Notification (3) Keepalive (4) Route Refresh (5) Defined in RFC by Xantaro

15 BGP Open Message Allows BGP peers to negotiate session parameters Hold time Authentication data Capabilities Support for Network Layer Reachability Information (NLRI) 15 by Xantaro

16 BGP Update Message Update messages contain a single set of BGP attributes and a couple of prefixes using those attributes BGP Attributes are encoded using TLV syntax Update messages may contain prefixes which are no longer valid (withdrawn routes) 16 by Xantaro

17 BGP Notification Messages When BGP peer detects an error, it sends a notification message and immediately closes both the BGP and TCP session Notification message contains the reason for closing the session 17 by Xantaro

18 Notification Error Codes and Subcodes Code Subcode Description Code Subcode Description 1 Message Header Error 3 Update Message Error 1 Connection not synchronized 1 Malformed attribute 2 Bad message length 2 Unrec. well-known attribute 3 Bad message type 3 Missing well-known attribute 2 Open Message Error 4 Attribute flag error 1 Unsupported version 5 Attribute length error 2 Bad peer AS 6 Invalid ORIGIN attribute 3 Bad BGP Identifier 8 Invalid NEXT_HOP attribute 4 Unsupported optional Parameter 9 Optional attribute error 5 Authentication failure 10 Invalid network field 6 Unacceptable hold timer 11 Malformed AS_PATH 7 Unsupported Capability 4 Hold timer 5 Finite State Machine Error 6 Cease 18 by Xantaro

19 BGP Keepalive Messages BGP does not use any TCP-based keepalive messages to determine if peer is reachable BGP Keepalive messages are sent one third of the hold timer If hold timer is set to zero, no BGP Keepalive messages are exchanged 19 by Xantaro

20 BGP Route Refresh Messages Route refresh messages are sent to a peer to request retransmission of previously sent BGP updates When willing to accept route refresh messages from its peer, BGP speaker should advertise the Route Refresh capability This is useful if routing filters were updated to re-evaluate the routing policy some prefixes might have been dropped with the old policy and the new policy might allow them 20 by Xantaro

21 BGP Capability Advertisement BGP Capability Advertisement instead of mapping a set of supported features to a particular version of BGP Defined in RFC 3392 Advertise support for each such feature at the BGP session establishment BGP Capability Advertisement provides a more flexible (and direct) way of introducing new features BGP Multiprotocol extensions were the first application of BGP Capability Advertisement, not the last one Thanks to BGP Capability Advertisement, today we still have BGPv4 21 by Xantaro

22 BGP Attributes Four basic types of BGP attributes Well-known mandatory attributes: these attributes must be recognized by all BGP speakers and must be included in all update messages. Well-known discretionary attributes: these attributes must be recognized by all BGP speakers and may be carried in updates but are not required in every update. Optional transitive attributes: these attributes may be recognized by some BGP speakers, but not all. They should be preserved and advertised to all peers whether or not they are recognized. Optional non-transitive attributes: these attributes may be recognized by some BGP speakers, but not all. If an update containing an optional transitive attribute is received, the update should be advertised to peers without the unrecognized attributes. 22 by Xantaro

23 BGP Attribute Overview Value Code Ref. Value Code Ref. 1 ORIGIN RFC CLUSTER_LIST RFC AS_PATH RFC DPA unused 3 NEXT_HOP RFC ADVERTISER RFC MULTI_EXIT_DISC RFC CLUSTER_ID RFC LOCAL_PREF RFC MP_REACH_NLRI RFC ATOMIC_ AGGREGATOR RFC MP_UNREACH_NLRI RFC AGGREGATOR RFC EXTENDED COMMUNITIES RFC COMMUNITY RFC AS4_PATH RFC ORIGINATOR_ID RFC AS4_AGGREGATOR RFC by Xantaro

24 BGP Attributes: Origin Code Well-known mandatory attribute Attribute is generated by the BGP speaker that originates the routing information and should not be changed Describes how the prefix was injected into BGP IGP (0): prefix was originated from interior gateway protocol EGP (1): prefix was originated from exterior gateway protocol (RFC 904) INCOMPLETE (2): prefix was originated by unknown source Lower Value is preferred IGP is better than EGP EGP is better than incomplete 24 by Xantaro

25 BGP Attributes: AS_PATH AS_PATH attribute contains a sequence of autonomous system numbers that represent the path a route has traversed Attribute is modified only when a route is advertised to an ebgp peer. Each AS prepends its own AS number to the path. routes with shorter AS-PATH are preferred (each AS counts as one, regardless of it s numerical value) 25 by Xantaro

26 BGP Attributes: NEXT_HOP NEXT_HOP attribute carries the IP address of the next hop router to the route destination By default, NEXT_HOP is only modified across ebgp sessions Local router performs recursive lookup to find route to BGP next hop 26 by Xantaro

27 Excurse on NEXT_HOP All ebgp peers must be reachable by all BGP-speaking routers within an autonomous system due to NEXT_HOP behavior across ibgp session 1. Redistribute connected interface to outside world into IGP 2. Include links to ebgp neighbors into IGP and make them passive Alternate design: modify NEXT_HOP processing at the network edge Make edge routers announce themselves as next hop 27 by Xantaro

28 BGP Attributes: Multiple Exit Discriminator Prior to BGP-4, attribute was called inter-as metric MED is designed to be a tiebreaker for routes received from different external peers in the same AS 28 by Xantaro

29 BGP Attributes: Local Preference Determines the preferred exit out of the autonomous system Local Preference only used with ibgp Default value is 100 if not specified, higher value is more preferred dropped whenever a route is forwarded with ebgp 29 by Xantaro

30 BGP Attributes: Communities A community is a group of destinations which share some common properties Before communities, route control was based on IP prefixes and AS_PATH only Communities simply control routing information Each AS can define which communities a prefix belongs to. By default, all prefixes belong to the Internet community. Administrators may use communities to tag, identify, filter or manipulate routes No automatic action based on community values (except for predefined communities) Predefined communities NO_EXPORT (0xFFFFFF01) instructs receiving BGP router to not advertise this route to external BGP peers NO_ADVERTISE (0xFFFFFF02) instructs receicing BGP router to not advertise the route to any BGP peer NO_EXPORT_SUBCONF (0xFFFFFF03) instructs receiving BGP router to not advertise the route to external BGP peers (AS external and confederation external) 30 by Xantaro

31 BGP Community Encoding 32-bit integers are not easy to handle More common convention is to split into two 16-bit values First value defines the scope of the community, i.e. it describes for which network the information is provided (and helps preventing conflicting) Second value is an arbitrary tag for the target network Example: 65001:1234 Used by AS65001 Community value within this scope is 1234 Problematic if you have a 32bit AS number RFC 8092 defined a new community format with 96 bit first 32 bit used as global administrator (can encode 32 bit AS numbers) remaining 64 bit can be used as community value defined as optional transitive attribute 31 by Xantaro

32 BGP Route Selection Process A router will use the following list to compare equal prefixes and find a best path: 1. Exclude routes with the local AS number in the AS-PATH (loop) 2. Exclude routes with inaccessible Next_Hop attribute value 3. Prefer highest Local Preference 4. Prefer shortest AS Path length 5. Prefer lowest Origin attribute value 6. Prefer lowest Multiple Exit Discriminator (MED) attribute value 7. Prefer external paths (ebgp) over internal paths (ibgp) - (aka as hot potatoes routing) 8. For ibgp paths, prefer path with lowest IGP metric to the advertised BGP Next Hop. 9. Prefer shortest Cluster-List length (if Route reflection is used) 10. Prefer route from the peer with the lowest Router ID 11. Prefer route from the peer with the lowest Peer Address. 32 by Xantaro

33 Scaling ibgp Implementation All BGP speakers within a single AS must be fully meshed Loop prevention is only working between autonomous systems (block routes with our own AS in the AS-path list) this results in a simple split horizon rule Routes received from internal BGP (ibgp) peers may be forwarded to external peers, but must not be forwarded to other internal BGP (ibgp) peers Routes received from external BGP (ebgp) peers may be forwarded to external and internal peers As a consequence, BGP speakers need to be fully meshed inside an AS For N BGP speakers, a total number of N*(N-1)/2 sessions are required Obviously this does not scale well in large networks, therefore 2 Scaling methods exists: Route Reflectors (commonly used today) Confederations (more exotic) 33 by Xantaro

34 Route Reflectors Remember: ibgp Split Horizon Route reflectors are designed to simplify the network allow easy transition from full-mesh to new topology to be backward compatible in case some routers do not understand route reflection Route reflectors are allowed to re-advertise (or reflect) ibgp-learned routes to some other ibgp neighbors 34 by Xantaro

35 Route Reflector Operation Internal neighbors of a route reflector are either clients or non-clients Routes received from non-clients are reflected to clients only Routes received from clients are reflected to clients and non-clients Route reflector and its clients form a cluster Non-Clients are considered to be fully meshed between each other, hence no reflection from non-client to other non-clients 35 by Xantaro

36 Route Reflector Redundancy Route reflectors could be single point of failure BGP speaker can be client to multiple route reflectors Setup at least two route reflectors for redundancy Full mesh route reflectors! 36 by Xantaro

37 Solving Route Reflector Loops Possible routing loops are avoided by using new BGP attributes ORIGINATOR_ID is set to the BGP Identifier of the originator within the local AS CLUSTER_LIST is a sequence of cluster IDs representing the reflection path 37 by Xantaro

38 Route Reflection Loss of Visibility A Route Reflector will only reflect best routes according to it s local view Consider a Route Reflector located in Munich that is getting equal BGP routes from peerings in Berlin and Stuttgart According to the IGP metric, Munich can reach Stuttgart with a metric of 100 Berlin with a metric of 1000 Hamburg with a metric of 1100 Munich will follow BGP bestpath selection process to find the best prefix for it s own routing decision for reflection to route reflector clients Hamburg Berlin 1000 Stuttgart Munich (Route Reflector for all other routers) Picture by wikipedia : 38 by Xantaro

39 Route Reflection Loss of Visibility Two identical Prefixes are received from Hamburg and Berlin 1. both routes have no AS-loop 2. both routes have valid (known by IGP) nexthops 3. both routes have default local preference (100) Hamburg /24 AS-PATH = Next-Hop = Loopback Stuttgart Berlin 4. both routes have AS-Paths of equal length 5. both routes have IGP as origin code 6. both routes have no Multiple Exit Discriminator (MED) 7. both routes are recieved from ibgp peers 8. IGP metric to Stuttgart is smaller than to Berlin This decision is not optimal for Hamburg /24 AS-PATH = Next-Hop = Loopback Stuttgart Stuttgart Munich (Route Reflector for all other routers) /24 AS-PATH = Next-Hop = Loopback Berlin Picture by wikipedia : 39 by Xantaro

40 Using geographically distributed route reflectors One solution is to locate route reflectors in each geographical region In this case Hamburg is made a route reflector as well as Munich As a consequence, Hamburg can see both prefixes and make a local bestpath decision Problems does not scale well in larger networks with increasing number of route reflectors, the design get s similar as ibgp full-mesh with the same challenges Hamburg /24 AS-PATH = Next-Hop = Loopback Stuttgart /24 AS-PATH = Next-Hop = Loopback Stuttgart /24 AS-PATH = Next-Hop = Loopback Berlin Berlin /24 AS-PATH = Next-Hop = Loopback Berlin Stuttgart Munich (Route Reflector for all other routers) Picture by wikipedia : 40 by Xantaro

41 Using BGP-Add-path RFC7911 defines the advertisement of multiple paths to a BGP neighbor Munich can send both paths to Hamburg without making a local selection Hamburg can now make a routing decision based on local IGP metric Problems increases the amount of routing information on route reflector clients Needs to be understood by route reflector client as it uses a different encoding of next-hop attribute (negotiated with capability advertisement) Hamburg /24 AS-PATH = Next-Hop = Loopback Stuttgart /24 AS-PATH = Next-Hop = Loopback Stuttgart /24 AS-PATH = Next-Hop = Loopback Berlin Berlin Stuttgart Munich (Route Reflector for all other routers) /24 AS-PATH = Next-Hop = Loopback Berlin Picture by wikipedia : 41 by Xantaro

42 Using Optimal Route Reflection defined by draft-ietf-idr-bgp-optimal-routereflection-13 Based on topology information of IGP Before reflecting a route towards Hamburg, Munich will check which path is better (from IGP perspective) for Hamburg Only path from Berlin is send to Hamburg due to closer IGP metric from Hamburg to Berlin Does not need special support in route reflector clients, as it is a local decision by the RR Problems increases the processing on the route reflector only works effective within the same IGP area Hamburg /24 AS-PATH = Next-Hop = Loopback Stuttgart /24 AS-PATH = Next-Hop = Loopback Berlin Berlin Stuttgart Munich (Route Reflector for all other routers) /24 AS-PATH = Next-Hop = Loopback Berlin Picture by wikipedia : 42 by Xantaro

43 Hierarchical Route Reflector-Design Route Reflectors themselves can be clients to other route reflectors Scalability can be improved by building hierarchical route reflector designs 43 by Xantaro

44 Confederations Alternative to ibgp Route Reflection Breaks a global autonomous system into multiple pieces (sub-as) Within each sub-as Use private AS numbers ibgp full-mesh topology is still required (may use route relection within sub-as) Between each sub-as: ebgp-type configurations (CBGP) are required Most ibgp parameters are not changed. However, AS_PATH attribute is modified to prevent loops Global AS is still viewed externally as a single AS 44 by Xantaro

45 Confederation Peering 45 by Xantaro

46 46 by Xantaro BGP BESTPATH SELECTION EXAMPLES

47 Examples for BGP bestpath Selection The following slides show examples on how BGP will select it s best routes with some examples In all examples we will assume that the next-hop is valid (known by IGP or a directly connected interface) the local AS of the router which is checking the routes is 100 Remember that his process will only start for identical prefixes (IP Subnet Address and subnet mask is the same The following slides show examples where two prefixes are compared, the process for comparing more similar prefixes is analogue 47 by Xantaro

48 Example 1 Prefixes received by AS 100 IP Prefix : /24 AS-Path : same Prefix 1. no loop 4. same length IP Prefix : /24 AS-Path : Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : same local pref 5. same origin 6. same MED 7. same type (ebgp) 8. not relevant (ebgp) 9. same list 10. smaller ID 11. not checked Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : Result : Left Prefix selected because Router ID of advertising router is smaller 48 by Xantaro

49 Example 2 Prefixes received by AS 100 IP Prefix : /24 AS-Path : not checked 1. AS loop! 4. not checked IP Prefix : /24 AS-Path : Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : not checked 5. not checked 6. not checked 7. not checked 8. not checked 9. not checked 10. not checked 11. not checked Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : Result : Right Prefix selected because AS-Path of left prefix contains local AS. 49 by Xantaro

50 Example 3 Prefixes received by AS 100 IP Prefix : /24 AS-Path : same Prefix 1. no loop 4. same length IP Prefix : /24 AS-Path : Local Preference : 100 Origin : IGP MED: not set learned via : ibgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : same local pref 5. same origin 6. same MED 7. prefer ebgp 8. not checked 9. not checked 10. not checked 11. not checked Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : Result : Right Prefix selected because ebgp is preferred over ibgp (hot potato routing) 50 by Xantaro

51 Example 4 Prefixes received by AS 100 IP Prefix : /24 AS-Path : same Prefix 1. no loop 4. same length IP Prefix : /24 AS-Path : Local Preference : 100 Origin : IGP MED: 100 learned via : ibgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : same local pref 5. same origin 6. different MED 7. not checked 8. not checked 9. not checked 10. not checked 11. not checked Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : Result : Depends on Routing Platform and / or configuration. Missing MED can be interpreted as worst (very high) or 0 (very low). Typically it considered as 0, in which case the right prefix would be preferred. 51 by Xantaro

52 Example 5 Prefixes received by AS 100 IP Prefix : /24 AS-Path : same Prefix 1. no loop 4. shorter AS-Path IP Prefix : /24 AS-Path : Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : same local pref 5. not checked 6. not checked 7. not checked 8. not checked 9. not checked 10. not checked 11. not checked Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : Result : Left Prefix selected because AS-Path is shorter (3 AS versus 4 AS) 52 by Xantaro

53 Example 6 Prefixes received by AS 100 IP Prefix : /24 AS-Path : same Prefix 1. no loop 4. not checked IP Prefix : /24 AS-Path : Local Preference : 100 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : higher pref 5. not checked 6. not checked 7. not checked 8. not checked 9. not checked 10. not checked 11. not checked Local Preference : 1000 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : Result : Right Prefix selected because Local Preference is higher (even AS path of right prefix is longer) 53 by Xantaro

54 Example 7 Prefixes received by AS 100 IP Prefix : /25 AS-Path : different Prefix 1. no loop 4. not checked IP Prefix : /24 AS-Path : Local Preference : 500 Origin : IGP MED: not set learned via : ibgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : not checked 5. not checked 6. not checked 7. not checked 8. not checked 9. not checked 10. not checked 11. not checked Local Preference : 120 Origin : IGP MED: not set learned via : ebgp IGP Metric to next-hop : 10 Cluster-List : not set Peer Router ID : Peer Address : Result : Both Prefixes are accepted, as they have different Subnet Masks. IP Traffic to will use left prefix, traffic to the right prefix 54 by Xantaro

55 Outlook BGP was also adopted to carry information for other protocols as IPv4 Non-IPv4 protocols are encoded using Address Family Identifier (AFI) Multiprotocol BGP support is advertised using capability advertisement Other uses include transmitting VPN information across a provider core network MPLS Layer 3 VPN labels MPLS Layer 2 VPN labels MPLS EVPN Labels MPLS Labeled Unicast IPv6 over IPv4 BGP Sessions 55 by Xantaro

Configuring BGP community 43 Configuring a BGP route reflector 44 Configuring a BGP confederation 44 Configuring BGP GR 45 Enabling Guard route

Configuring BGP community 43 Configuring a BGP route reflector 44 Configuring a BGP confederation 44 Configuring BGP GR 45 Enabling Guard route Contents Configuring BGP 1 Overview 1 BGP speaker and BGP peer 1 BGP message types 1 BGP path attributes 2 BGP route selection 6 BGP route advertisement rules 6 BGP load balancing 6 Settlements for problems

More information

BGP Configuration. BGP Overview. Introduction to BGP. Formats of BGP Messages. Header

BGP Configuration. BGP Overview. Introduction to BGP. Formats of BGP Messages. Header Table of Contents BGP Configuration 1 BGP Overview 1 Introduction to BGP 1 Formats of BGP Messages 1 BGP Path Attributes 4 BGP Route Selection 8 Configuring BGP 8 Configuration Prerequisites 8 Configuration

More information

Protecting an EBGP peer when memory usage reaches level 2 threshold 66 Configuring a large-scale BGP network 67 Configuring BGP community 67

Protecting an EBGP peer when memory usage reaches level 2 threshold 66 Configuring a large-scale BGP network 67 Configuring BGP community 67 Contents Configuring BGP 1 Overview 1 BGP speaker and BGP peer 1 BGP message types 1 BGP path attributes 2 BGP route selection 6 BGP route advertisement rules 6 BGP load balancing 6 Settlements for problems

More information

BGP. BGP Overview. Formats of BGP Messages. I. Header

BGP. BGP Overview. Formats of BGP Messages. I. Header Overview Three early versions of are -1 (RFC1105), -2 (RFC1163) and -3 (RFC1267). The current version in use is -4 (RFC1771). -4 is rapidly becoming the defacto Internet exterior routing protocol standard

More information

Table of Contents. BGP Configuration 1

Table of Contents. BGP Configuration 1 Table of Contents BGP Configuration 1 BGP Overview 1 Formats of BGP Messages 2 BGP Path Attributes 5 BGP Route Selection 9 ibgp and IGP Synchronization 11 Settlements for Problems in Large Scale BGP Networks

More information

Configuration prerequisites 45 Configuring BGP community 45 Configuring a BGP route reflector 46 Configuring a BGP confederation 46 Configuring BGP

Configuration prerequisites 45 Configuring BGP community 45 Configuring a BGP route reflector 46 Configuring a BGP confederation 46 Configuring BGP Contents Configuring BGP 1 Overview 1 BGP speaker and BGP peer 1 BGP message types 1 BGP path attributes 2 BGP route selection 6 BGP route advertisement rules 6 BGP load balancing 6 Settlements for problems

More information

Table of Contents 1 BGP Configuration 1-1

Table of Contents 1 BGP Configuration 1-1 Table of Contents 1 BGP Configuration 1-1 BGP Overview 1-1 Formats of BGP Messages 1-2 BGP Path Attributes 1-4 BGP Route Selection 1-8 ibgp and IGP Synchronization 1-11 Settlements for Problems in Large

More information

Routing Between Autonomous Systems (Example: BGP4) RFC 1771

Routing Between Autonomous Systems (Example: BGP4) RFC 1771 CS 4/55231 Internet Engineering Kent State University Dept. of Computer Science LECT-7B Routing Between Autonomous Systems (Example: BGP4) RFC 1771 52 53 BGP4 Overview Example of Operations BGP4 is a path

More information

Internet Interconnection Structure

Internet Interconnection Structure Internet Interconnection Structure Basic Concepts (1) Internet Service Provider (ISP) Provider who connects an end user customer with the Internet in one or few geographic regions. National & Regional

More information

BGP. Autonomous system (AS) BGP version 4

BGP. Autonomous system (AS) BGP version 4 BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 1.5, 2011/03/06 13:35:28) Monday, March 7, 2011 General ideas behind BGP Background Providers,

More information

BGP. Autonomous system (AS) BGP version 4

BGP. Autonomous system (AS) BGP version 4 BGP Border Gateway Protocol (an introduction) dr. C. P. J. Koymans Informatics Institute University of Amsterdam March 11, 2008 General ideas behind BGP Background Providers, Customers and Peers External

More information

BGP. Autonomous system (AS) BGP version 4

BGP. Autonomous system (AS) BGP version 4 BGP Border Gateway Protocol (an introduction) dr. C. P. J. Koymans Informatics Institute University of Amsterdam (version 1.3, 2010/03/10 20:05:02) Monday, March 8, 2010 General ideas behind BGP Background

More information

BGP Attributes (C) Herbert Haas 2005/03/11 1

BGP Attributes (C) Herbert Haas 2005/03/11 1 BGP Attributes (C) Herbert Haas 2005/03/11 1 Attribute Types Well-known Optional Mandatory Discretionary Non-Transitive Transitive ORIGIN (1) AS_PATH (2) NEXT_HOP (3) LOCAL_PREFERENCE (5) ATOMIC_AGGREGATE

More information

internet technologies and standards

internet technologies and standards Institute of Telecommunications Warsaw University of Technology internet technologies and standards Piotr Gajowniczek BGP (Border Gateway Protocol) structure of the Internet Tier 1 ISP Tier 1 ISP Google

More information

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System)

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System) BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 1.9, 2012/03/14 10:21:22) Monday, March 12, 2012 General ideas behind BGP Background Providers,

More information

IBGP internals. BGP Advanced Topics. Agenda. BGP Continuity 1. L49 - BGP Advanced Topics. L49 - BGP Advanced Topics

IBGP internals. BGP Advanced Topics. Agenda. BGP Continuity 1. L49 - BGP Advanced Topics. L49 - BGP Advanced Topics IBGP internals BGP Advanced Topics main IBGP aspects inside an AS continuity all packets entering the AS that were not blocked by some policies should reach the proper exit BGP router all transit routers

More information

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System)

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System) BGP Border Gateway Protocol A short introduction Karst Koymans Informatics Institute University of Amsterdam (version 18.3, 2018/12/03 13:53:22) Tuesday, December 4, 2018 General ideas behind BGP Background

More information

BGP. Attributes 2005/03/11. (C) Herbert Haas

BGP. Attributes 2005/03/11. (C) Herbert Haas BGP Attributes (C) Herbert Haas 2005/03/11 Attribute Types Well-known Optional Mandatory Discretionary Non-Transitive Transitive ORIGIN (1) AS_PATH (2) NEXT_HOP (3) LOCAL_PREFERENCE (5) ATOMIC_AGGREGATE

More information

Configuring BGP. Cisco s BGP Implementation

Configuring BGP. Cisco s BGP Implementation Configuring BGP This chapter describes how to configure Border Gateway Protocol (BGP). For a complete description of the BGP commands in this chapter, refer to the BGP s chapter of the Network Protocols

More information

Operation Manual BGP. Table of Contents

Operation Manual BGP. Table of Contents Table of Contents Table of Contents... 1-1 1.1 BGP/MBGP Overview... 1-1 1.1.1 Introduction to BGP... 1-1 1.1.2 BGP Message Types... 1-2 1.1.3 BGP Routing Mechanism... 1-2 1.1.4 MBGP... 1-3 1.1.5 BGP Peer

More information

Connecting to a Service Provider Using External BGP

Connecting to a Service Provider Using External BGP Connecting to a Service Provider Using External BGP First Published: May 2, 2005 Last Updated: August 21, 2007 This module describes configuration tasks that will enable your Border Gateway Protocol (BGP)

More information

BGP. Border Gateway Protocol A short introduction. Karst Koymans. Informatics Institute University of Amsterdam. (version 18.3, 2018/12/03 13:53:22)

BGP. Border Gateway Protocol A short introduction. Karst Koymans. Informatics Institute University of Amsterdam. (version 18.3, 2018/12/03 13:53:22) BGP Border Gateway Protocol A short introduction Karst Koymans Informatics Institute University of Amsterdam (version 18.3, 2018/12/03 13:53:22) Tuesday, December 4, 2018 Karst Koymans (UvA) BGP Tuesday,

More information

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System)

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System) BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 310, 2014/03/11 10:50:06) Monday, March 10, 2014 General ideas behind BGP Background Providers,

More information

BGP. Border Gateway Protocol (an introduction) Karst Koymans. Informatics Institute University of Amsterdam. (version 17.3, 2017/12/04 13:20:08)

BGP. Border Gateway Protocol (an introduction) Karst Koymans. Informatics Institute University of Amsterdam. (version 17.3, 2017/12/04 13:20:08) BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 17.3, 2017/12/04 13:20:08) Tuesday, December 5, 2017 Karst Koymans (UvA) BGP Tuesday,

More information

Connecting to a Service Provider Using External BGP

Connecting to a Service Provider Using External BGP Connecting to a Service Provider Using External BGP This module describes configuration tasks that will enable your Border Gateway Protocol (BGP) network to access peer devices in external networks such

More information

TELE 301 Network Management

TELE 301 Network Management TELE 301 Network Management Lecture 24: Exterior Routing and BGP Haibo Zhang Computer Science, University of Otago TELE301 Lecture 16: Remote Terminal Services 1 Today s Focus How routing between different

More information

Inter-Domain Routing: BGP

Inter-Domain Routing: BGP Inter-Domain Routing: BGP Richard T. B. Ma School of Computing National University of Singapore CS 3103: Compute Networks and Protocols Inter-Domain Routing Internet is a network of networks Hierarchy

More information

Border Gateway Protocol (an introduction) Karst Koymans. Monday, March 10, 2014

Border Gateway Protocol (an introduction) Karst Koymans. Monday, March 10, 2014 .. BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 3.10, 2014/03/11 10:50:06) Monday, March 10, 2014 Karst Koymans (UvA) BGP Monday, March

More information

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System)

BGP. Autonomous system (AS) BGP version 4. Definition (AS Autonomous System) BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 16.4, 2017/03/13 13:32:49) Tuesday, March 14, 2017 General ideas behind BGP Background

More information

Border Gateway Protocol (an introduction) Karst Koymans. Tuesday, March 8, 2016

Border Gateway Protocol (an introduction) Karst Koymans. Tuesday, March 8, 2016 .. BGP Border Gateway Protocol (an introduction) Karst Koymans Informatics Institute University of Amsterdam (version 15.6, 2016/03/15 22:30:35) Tuesday, March 8, 2016 Karst Koymans (UvA) BGP Tuesday,

More information

Border Gateway Protocol

Border Gateway Protocol 39 CHAPTER Chapter Goals Understand the purpose of the. Explain BGP attributes and their use in route selection. Examine the BGP route selection process. Introduction The (BGP) is an interautonomous system

More information

Multiprotocol BGP (MBGP)

Multiprotocol BGP (MBGP) Multiprotocol BGP (MBGP) Module 5 2000, Cisco Systems, Inc. 1 Copyright 1998-2000, Cisco Systems, Inc. Module5.ppt 1 Module Objectives Understand that MBGP is NOT a replacement for PIM Understand the basic

More information

Introduction. Keith Barker, CCIE #6783. YouTube - Keith6783.

Introduction. Keith Barker, CCIE #6783. YouTube - Keith6783. Understanding, Implementing and troubleshooting BGP 01 Introduction http:// Instructor Introduction Keith Barker, CCIE #6783 CCIE Routing and Switching 2001 CCIE Security 2003 kbarker@ine.com YouTube -

More information

Module 6 Implementing BGP

Module 6 Implementing BGP Module 6 Implementing BGP Lesson 1 Explaining BGP Concepts and Terminology BGP Border Gateway Protocol Using BGP to Connect to the Internet If only one ISP, do not need BGP. If multiple ISPs, use BGP,

More information

The Border Gateway Protocol

The Border Gateway Protocol 5810ch01.qxd_kp 5/28/04 3:27 PM Page 1 1 The Border Gateway Protocol When networks were small, there was no concept of interior and exterior gateway protocols; a network ran a routing protocol, and that

More information

HP Load Balancing Module

HP Load Balancing Module HP Load Balancing Module Appendix Protocol Reference Part number: 5998-4222 Software version: Feature 3221 Document version: 6PW100-20130326 Legal and notice information Copyright 2013 Hewlett-Packard

More information

BGP Route Reflector Commands

BGP Route Reflector Commands This chapter provides details of the commands used for configuring Border Gateway Protocol (BGP) Route Reflector (RR). address-family (BGP), on page 2 keychain, on page 5 neighbor (BGP), on page 7 remote-as

More information

Internet Routing Protocols Lecture 03 Inter-domain Routing

Internet Routing Protocols Lecture 03 Inter-domain Routing Internet Routing Protocols Lecture 03 Inter-domain Routing Advanced Systems Topics Lent Term, 2008 Timothy G. Griffin Computer Lab Cambridge UK Autonomous Routing Domains A collection of physical networks

More information

BGP can also be used for carrying routing information for IPv6 prefix over IPv6 networks.

BGP can also be used for carrying routing information for IPv6 prefix over IPv6 networks. This chapter describes how to configure the Cisco ASA to route data, perform authentication, and redistribute routing information using the Border Gateway Protocol (). About, page 1 Guidelines for, page

More information

The Contemporary Internet p. 3 Evolution of the Internet p. 5 Origins and Recent History of the Internet p. 5 From ARPANET to NSFNET p.

The Contemporary Internet p. 3 Evolution of the Internet p. 5 Origins and Recent History of the Internet p. 5 From ARPANET to NSFNET p. The Contemporary Internet p. 3 Evolution of the Internet p. 5 Origins and Recent History of the Internet p. 5 From ARPANET to NSFNET p. 7 The Internet Today p. 8 NSFNET Solicitations p. 10 Network Access

More information

Chapter 13 Configuring BGP4

Chapter 13 Configuring BGP4 Chapter 13 Configuring BGP4 This chapter provides details on how to configure Border Gateway Protocol version 4 (BGP4) on HP products using the CLI and the Web management interface. BGP4 is supported on

More information

This appendix contains supplementary Border Gateway Protocol (BGP) information and covers the following topics:

This appendix contains supplementary Border Gateway Protocol (BGP) information and covers the following topics: Appendix C BGP Supplement This appendix contains supplementary Border Gateway Protocol (BGP) information and covers the following topics: BGP Route Summarization Redistribution with IGPs Communities Route

More information

Ravi Chandra cisco Systems Cisco Systems Confidential

Ravi Chandra cisco Systems Cisco Systems Confidential BGP4 1 Ravi Chandra cisco Systems 0799_04F7_c2 Cisco Systems Confidential 2 Border Gateway Protocol (BGP) Introduction to BGP BGP Peer Relationship BGP Attributes Applying Policy with BGP Putting it all

More information

Chapter 1. Getting Started

Chapter 1. Getting Started Versatile Routing and Services with BGP: Understanding and Implementing BGP in SR-OS PREV Introduction NEXT Chapter 2: BGP/MPLS IP-VPN Chapter 1 Getting Started Although this book does not discuss the

More information

Configuring Internal BGP Features

Configuring Internal BGP Features This module describes how to configure internal Border Gateway Protocol (BGP) features. Internal BGP (ibgp) refers to running BGP on networking devices within one autonomous system. BGP is an interdomain

More information

Copyright 1998, Cisco Systems, Inc. All rights reserved. Printed in USA. 0945_05F9_c1.scr 1. RST _05_2001_c1

Copyright 1998, Cisco Systems, Inc. All rights reserved. Printed in USA. 0945_05F9_c1.scr 1. RST _05_2001_c1 3003_05_2001_c1 2001, Cisco Systems, Inc. All rights reserved. 1 0945_05F9_c1.scr 1 Introduction to BGP Scalable, Stable, Simple Session 3003_05_2001_c1 2001, Cisco Systems, Inc. All rights reserved. 3

More information

LACNIC XIII. Using BGP for Traffic Engineering in an ISP

LACNIC XIII. Using BGP for Traffic Engineering in an ISP LACNIC XIII Using BGP for Traffic Engineering in an ISP Program Using BGP Attributes Implementing IBGP Implementing EBGP Emphasis in Stability, Scalability and Configuration Examples BGP Review Why use

More information

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355 BGP Commands Use the commands in this chapter to configure and monitor Border Gateway Protocol (BGP). For BGP configuration information and examples, refer to the Configuring BGP chapter of the Network

More information

BGP Routing and BGP Policy. BGP Routing. Agenda. BGP Routing Information Base. L47 - BGP Routing. L47 - BGP Routing

BGP Routing and BGP Policy. BGP Routing. Agenda. BGP Routing Information Base. L47 - BGP Routing. L47 - BGP Routing BGP Routing and BGP Policy BGP Routing The BGP Routing Principles and Route Decisions based on AS-Path in a simple topology of AS s routing policy is reduced to a minimal function demonstrated in example

More information

FiberstoreOS BGP Command Line Reference

FiberstoreOS BGP Command Line Reference FiberstoreOS BGP Command Line Reference Contents 1 BGP Commands...1 1.1 address-family...1 1.2 aggregate-address...2 1.3 bgp always-compare-med... 2 1.4 bgp bestpath as-path ignore...3 1.5 bgp bestpath

More information

Internet Routing Protocols Lecture 01 & 02

Internet Routing Protocols Lecture 01 & 02 Internet Routing Protocols Lecture 01 & 02 Advanced Systems Topics Lent Term, 2010 Timothy G. Griffin Computer Lab Cambridge UK Internet Routing Outline Lecture 1 : Inter-domain routing architecture, the

More information

BGP Attributes and Path Selection

BGP Attributes and Path Selection BGP Attributes and Path Selection ISP Training Workshops 1 BGP Attributes The tools available for the job 2 What Is an Attribute?... Next Hop AS Path MED...... Part of a BGP Update Describes the characteristics

More information

Internet inter-as routing: BGP

Internet inter-as routing: BGP Internet inter-as routing: BGP BGP (Border Gateway Protocol): the de facto standard BGP provides each AS a means to: 1. Obtain subnet reachability information from neighboring ASs. 2. Propagate the reachability

More information

Configuring a Basic BGP Network

Configuring a Basic BGP Network Configuring a Basic BGP Network This module describes the basic tasks to configure a basic Border Gateway Protocol (BGP) network. BGP is an interdomain routing protocol that is designed to provide loop-free

More information

Configuring a Basic BGP Network

Configuring a Basic BGP Network Configuring a Basic BGP Network Last Updated: October 19, 2011 This module describes the basic tasks to configure a basic Border Gateway Protocol (BGP) network. BGP is an interdomain routing protocol that

More information

Routing Protocols --- Exterior Gateway Protocol

Routing Protocols --- Exterior Gateway Protocol Content Routing Protocols --- Exterior Gateway Protocol Linda Wu (CMPT 471 23-3) Limiting router interaction Autonomous system BGP protocol BGP messages Other issues on BGP Reference: chapter 15 Notes-13

More information

Routing part 2. Electrical and Information Technology

Routing part 2. Electrical and Information Technology Routing part 2 Jens A Andersson Electrical and Information Technology Routing Introduction Inside the Router Unicast Routing Intra Domain Routing Inter Domain Routing MANET and AdHoc routing Multicast

More information

LARGE SCALE IP ROUTING LECTURE BY SEBASTIAN GRAF

LARGE SCALE IP ROUTING LECTURE BY SEBASTIAN GRAF LARGE SCALE IP ROUTING LECTURE BY SEBASTIAN GRAF MODULE 05 MULTIPROTOCOL LABEL SWITCHING (MPLS) AND LABEL DISTRIBUTION PROTOCOL (LDP) 1 by Xantaro IP Routing In IP networks, each router makes an independent

More information

Routing. Jens A Andersson Communication Systems

Routing. Jens A Andersson Communication Systems Routing Jens A Andersson Communication Systems R1 Choosing an Optimal Path R4 5 R7 5 10 40 R6 6 5 B R2 15 A 20 4 10 10 R8 R3 5 R5 10 Router A router is a type of internetworking device that passes data

More information

BGP. Inter-domain routing with the Border Gateway Protocol. Iljitsch van Beijnum Amsterdam, 13 & 16 March 2007

BGP. Inter-domain routing with the Border Gateway Protocol. Iljitsch van Beijnum Amsterdam, 13 & 16 March 2007 BGP Inter-domain routing with the Border Gateway Protocol Iljitsch van Beijnum Amsterdam, 13 & 16 March 2007 1 Routing Between ISPs Internal routing protocols don't work here: too much information So:

More information

PART III. Implementing Inter-Network Relationships with BGP

PART III. Implementing Inter-Network Relationships with BGP PART III Implementing Inter-Network Relationships with BGP ICNP 2002 Routing Protocols Autonomous System BGP-4 BGP = Border Gateway Protocol Is a Policy-Based routing protocol Is the de facto EGP of today

More information

H3C S9500 Series Routing Switches

H3C S9500 Series Routing Switches Operation Manual Hangzhou H3C Technologies Co., Ltd. http://www.h3c.com Manual Version: T2-081655-20080530-C-2.03 Product Version: S9500-CMW520-R2132 Copyright 2007-2008, Hangzhou H3C Technologies Co.,

More information

Configuring basic MBGP

Configuring basic MBGP Contents Configuring MBGP 1 MBGP overview 1 Protocols and standards 1 MBGP configuration task list 1 Configuring basic MBGP 2 Controlling route advertisement and reception 2 Configuration prerequisites

More information

MPLS VPN Multipath Support for Inter-AS VPNs

MPLS VPN Multipath Support for Inter-AS VPNs The feature supports Virtual Private Network (VPN)v4 multipath for Autonomous System Boundary Routers (ASBRs) in the interautonomous system (Inter-AS) Multiprotocol Label Switching (MPLS) VPN environment.

More information

Contents. BGP commands 1

Contents. BGP commands 1 Contents BGP commands 1 address-family ipv4 1 address-family ipv6 2 address-family link-state 3 advertise-rib-active 4 aggregate 5 balance 7 balance as-path-neglect 9 bestroute as-path-neglect 10 bestroute

More information

Routing Unicast routing protocols

Routing Unicast routing protocols Routing Unicast routing protocols Jens A Andersson Electrical and Information Technology R1 Choosing an Optimal Path R4 5 R7 5 10 40 R6 6 5 B R2 15 A 20 4 10 10 R8 R3 5 10 R5 1 Router A router is a type

More information

Configuring Advanced BGP

Configuring Advanced BGP CHAPTER 6 This chapter describes how to configure advanced features of the Border Gateway Protocol (BGP) on the Cisco NX-OS switch. This chapter includes the following sections: Information About Advanced

More information

CertifyMe. CertifyMe

CertifyMe. CertifyMe CertifyMe Number: 642-661 Passing Score: 800 Time Limit: 120 min File Version: 7.6 http://www.gratisexam.com/ CertifyMe-642-661 Exam A QUESTION 1 Exhibit: Certkiller router#show ip route Codes: C - connected,

More information

MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses

MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses MPLS VPN Inter-AS with ASBRs Exchanging VPN-IPv4 Addresses The Multiprotocol Label Switching (MPLS) VPN Inter-AS with Autonomous System Boundary Routers (ASBRs) Exchanging VPN-IPv4 Addresses feature allows

More information

Internetwork Expert s CCNP Bootcamp. Border Gateway Protocol (BGP) What Is BGP?

Internetwork Expert s CCNP Bootcamp. Border Gateway Protocol (BGP) What Is BGP? Internetwork Expert s CCNP Bootcamp Border Gateway Protocol (BGP) http:// What Is BGP? Border Gateway Protocol Version 4 Standards based RFC 4271 A Border Gateway Protocol 4 (BGP-4) Exterior Gateway Protocol

More information

Advanced Computer Networks

Advanced Computer Networks Advanced Computer Networks External Routing - BGP protocol Prof. Andrzej Duda duda@imag.fr Contents Autonomous systems Interconnection of ASs Path vector routing BGP types of AS protocol structure of BGP

More information

EE 122: Inter-domain routing Border Gateway Protocol (BGP)

EE 122: Inter-domain routing Border Gateway Protocol (BGP) EE 122: Inter-domain routing Border Gateway Protocol (BGP) Ion Stoica October 2, 2002 (* this presentation is based on Lakshmi Subramanian s slides) Big Picture Large ISP Large ISP St u b D i al - U p

More information

Obsoletes RFCs: 1105, 1163 T.J. Watson Research Center, IBM Corp. October 1991

Obsoletes RFCs: 1105, 1163 T.J. Watson Research Center, IBM Corp. October 1991 Network Working Group Request for Comments: 1267 Obsoletes RFCs: 1105, 1163 K. Lougheed cisco Systems Y. Rekhter T.J. Watson Research Center, IBM Corp. October 1991 Status of this Memo A Border Gateway

More information

BGP. BGP Overview. BGP Operation. BGP Neighbors

BGP. BGP Overview. BGP Operation. BGP Neighbors BGP BGP Overview BGP Operation BGP Neighbors BGP Overview AS - Autonomous Systems Multihoming IGP vs. EGP When to use BGP? 2 BGP Overview AS - Autonomous Systems Multihoming IGP vs. EGP When to use BGP?

More information

University of Belgrade - School of Electrical Engineering Department of Telecommunications

University of Belgrade - School of Electrical Engineering Department of Telecommunications University of Belgrade - School of Electrical Engineering Department of Telecommunications 1 BGP-4 Theory and Practice Berislav Todorović beri@etf.bg.ac.yu Nenad Krajnović krajko@etf.bg.ac.yu 2 Routers

More information

BGP Tutorial. APRICOT 2004, Kuala Lumpur February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved.

BGP Tutorial. APRICOT 2004, Kuala Lumpur February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved. BGP Tutorial Philip Smith , Kuala Lumpur February 2004 1 APRICOT BGP Tutorials Two Tutorials Part 1 Introduction Part 2 Multihoming Morning Afternoon 2 BGP Tutorial Part 1 Introduction Philip

More information

CS 640: Introduction to Computer Networks. Intra-domain routing. Inter-domain Routing: Hierarchy. Aditya Akella

CS 640: Introduction to Computer Networks. Intra-domain routing. Inter-domain Routing: Hierarchy. Aditya Akella CS 640: Introduction to Computer Networks Aditya Akella Lecture 11 - Inter-Domain Routing - BGP (Border Gateway Protocol) Intra-domain routing The Story So Far Routing protocols generate the forwarding

More information

BGP Tutorial. APRICOT 2003, Taipei February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved.

BGP Tutorial. APRICOT 2003, Taipei February Philip Smith APRICOT , Cisco Systems, Inc. All rights reserved. BGP Tutorial Philip Smith , Taipei February 2003 1 APRICOT BGP Tutorials Four Tutorials over Two Days Part 1 Introduction Monday morning Part 2 Deployment Monday afternoon Part 3 Multihoming

More information

Configuring BGP on Cisco Routers Volume 1

Configuring BGP on Cisco Routers Volume 1 Volume 1 I. Course Introduction A. Overview/Learner Skills and Knowledge B. Course Flow C. Additional References 1. Cisco Glossary of Terms D. Your Training Curriculum II. BGP Overview III. Introducing

More information

CS4450. Computer Networks: Architecture and Protocols. Lecture 15 BGP. Spring 2018 Rachit Agarwal

CS4450. Computer Networks: Architecture and Protocols. Lecture 15 BGP. Spring 2018 Rachit Agarwal CS4450 Computer Networks: Architecture and Protocols Lecture 15 BGP Spring 2018 Rachit Agarwal Autonomous System (AS) or Domain Region of a network under a single administrative entity Border Routers Interior

More information

IBGP scaling: Route reflectors and confederations

IBGP scaling: Route reflectors and confederations DD2491 p2 2009/2010 IBGP scaling: Route reflectors and confederations Olof Hagsand KTH /CSC 1 Literature Route Reflectors Practical BGP pages 135 153 RFC 4456 Confederations Practical BGP pages 153 160

More information

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355

BGP Commands. Network Protocols Command Reference, Part 1 P1R-355 BGP Commands Use the commands in this chapter to configure and monitor Border Gateway Protocol (BGP). For BGP configuration information and examples, refer to the Configuring BGP chapter of the Network

More information

Configuration - BGP Services Avaya Ethernet Routing Switch 5000 Series

Configuration - BGP Services Avaya Ethernet Routing Switch 5000 Series Configuration - BGP Services Avaya Ethernet Routing Switch 5000 Series Release 6.3 NN47200-511 01.02 October 2012 2012 Avaya Inc. All Rights Reserved. Notice While reasonable efforts have been made to

More information

Vendor: Alcatel-Lucent. Exam Code: 4A Exam Name: Alcatel-Lucent Border Gateway Protocol. Version: Demo

Vendor: Alcatel-Lucent. Exam Code: 4A Exam Name: Alcatel-Lucent Border Gateway Protocol. Version: Demo Vendor: Alcatel-Lucent Exam Code: 4A0-102 Exam Name: Alcatel-Lucent Border Gateway Protocol Version: Demo QUESTION 1 Upon the successful establishment of a TCP session between peers, what type of BGP message

More information

Multiprotocol BGP 1 MPLS VPN. Agenda. Multiprotocol BGP 2

Multiprotocol BGP 1 MPLS VPN. Agenda. Multiprotocol BGP 2 Multiprotocol BGP 1 MPLS VPN Peer to Peer VPN s BGP-4 (RFC 1771) is capable of carrying routing information only for IPv4 The only three pieces of information carried by BGP-4 that are IPv4 specific are

More information

Symbols. Numerics I N D E X

Symbols. Numerics I N D E X I N D E X Symbols? (question mark), CLI help system, 126 Numerics A 2-router BGP topology, configuring, 279 284 4-router BGP topology, configuring, 266, 276 279 ABRs (area border routers), 9, 87, 95, 141

More information

BGP Protocol & Configuration. Scalable Infrastructure Workshop AfNOG2008

BGP Protocol & Configuration. Scalable Infrastructure Workshop AfNOG2008 BGP Protocol & Configuration Scalable Infrastructure Workshop AfNOG2008 Border Gateway Protocol (BGP4) Case Study 1, Exercise 1: Single upstream Part 6: BGP Protocol Basics Part 7: BGP Protocol - more

More information

ibgp Multipath Load Sharing

ibgp Multipath Load Sharing This feature module describes the feature. This feature enables the BGP speaking router to select multiple ibgp paths as the best paths to a destination. The best paths or multipaths are then installed

More information

BGP-v4 Theory and Practice

BGP-v4 Theory and Practice BGP-v4 Theory and Practice Dr Nenad Krajnović krajko@etf.bg.ac.rs 1 BGP-4 Border Gateway Protocol (Principles of Operation) 2 BGP-4 (Border Gateway Protocol - RFC 1771, 4271) Exchanges inter-as routing

More information

Interdomain Routing Reading: Sections P&D 4.3.{3,4}

Interdomain Routing Reading: Sections P&D 4.3.{3,4} Interdomain Routing Reading: Sections P&D 4.3.{3,4} EE122: Intro to Communication Networks Fall 2006 (MW 4:00-5:30 in Donner 155) Vern Paxson TAs: Dilip Antony Joseph and Sukun Kim http://inst.eecs.berkeley.edu/~ee122/

More information

Internet Routing : Fundamentals of Computer Networks Bill Nace

Internet Routing : Fundamentals of Computer Networks Bill Nace Internet Routing 14-740: Fundamentals of Computer Networks Bill Nace Material from Computer Networking: A Top Down Approach, 6 th edition. J.F. Kurose and K.W. Ross Looking Ahead Lab #2 just due Quiz #2

More information

ISP Border Definition. Alexander Azimov

ISP Border Definition. Alexander Azimov ISP Border Definition Alexander Azimov ISP goal (one ASN) BGP Decision Process Step Attribute Transit 1 Highest Local Preference value Non-transit 2 Lowest AS Path length Transit 3 Lowest

More information

BGP Attributes and Policy Control

BGP Attributes and Policy Control BGP Attributes and Policy Control ISP/IXP Workshops 1 Agenda BGP Attributes BGP Path Selection Applying Policy 2 BGP Attributes The tools available for the job 3 What Is an Attribute?... Next Hop......

More information

BGP Attributes and Policy Control

BGP Attributes and Policy Control BGP Attributes and Policy Control ISP/IXP Workshops 1 Agenda BGP Attributes BGP Path Selection Applying Policy 2 BGP Attributes The tools available for the job 3 What Is an Attribute?... Next Hop......

More information

Implementing MPLS Layer 3 VPNs

Implementing MPLS Layer 3 VPNs A Multiprotocol Label Switching (MPLS) Layer 3 Virtual Private Network (VPN) consists of a set of sites that are interconnected by means of an MPLS provider core network. At each customer site, one or

More information

Chapter 17 BGP4 Commands

Chapter 17 BGP4 Commands Chapter 17 BGP4 Commands NOTE: This chapter describes commands in the BGP configuration level, which is present on HP devices that support IPv4 only. For information about BGP commands and configuration

More information

Architectures and Protocols for Integrated Networks. Intra-domain and Inter-domain Routing Protocols

Architectures and Protocols for Integrated Networks. Intra-domain and Inter-domain Routing Protocols Architectures and Protocols for Integrated Networks Intra-domain and Inter-domain Routing Protocols How is the routing table built? Path finding Paths from a device to any other device. Aggregated according

More information

Advanced Computer Networks

Advanced Computer Networks Advanced Computer Networks More on BGP Jianping Pan Summer 2007 7/4/07 csc485b/586b/seng480b 1 Review: BGP Border Gateway Protocol path vector routing prefix: AS-path policy-based routing import/export

More information

BGP Attributes and Policy Control

BGP Attributes and Policy Control BGP Attributes and Policy Control ISP/IXP `2005, Cisco Systems, Inc. All rights reserved. 1 Agenda BGP Attributes BGP Path Selection Applying Policy 2 BGP Attributes The tools available for the job `2005,

More information

Other Developments: CIDR

Other Developments: CIDR Other Developments: CIDR CIDR (classless Inter domain routing) Too many small networks requiring multiple class C addresses Running out of class B addresses, not enough nets in class A Assign contiguous

More information