Configuring OSPF in a single area. OSPF overview. Overview. Objectives. To understand how the OSPF protocol works

Transcription

1 Overview onfiguring OSPF in a single area Objectives Terminologies Different topology roadcast multi-access topology Point-to-point topology NM topology Written exercise: OSPF operation onfiguring OSPF in a single area Verifying OSPF operation Lab scenario: onfiguring OSPF in a single area Objectives To understand how the OSPF protocol works To be able to configure a router running OSPF protocol OSPF overview To be able to verify the operation of OSPF inside the network with different topology scenarios

2 Open Shortest Path First (OSPF) Open standard link state routing protocol (RF 1247, 2328) llows fast convergence of routes Supports VLSM Selects the path based on bandwidth Supports equal-cost multi-path OSPF IP packet To deliver routing information to neighboring router OSPF relies on IP packets and uses protocol port 89 Frame Header 89 = OSPF 6 = TP 16 = UDP IP Header Protocol Number Frame Payload TP Header Packet Payload Port No Segment Payload R Terminology utonomous systems rea ost Neighbors database Topology database Routing table Topologies roadcast Multiaccess Point-to-Point NM X.25 Frame Relay TM

3 neighboring routers neighboring router (cont.) D Hello Hello Kjhkajahdkjlkjd Router ID Hello/dead intervals * neighbors rea-id * Router priority DR IP address DR IP address uthentication password * Stub area flag * D Hello Hello entry match? Kjhkajahdkjlkjd Router ID Hello/dead intervals * neighbors rea-id * Router priority DR IP address DR IP address uthentication password * Stub area flag * Entry required must match on neighboring routers DR and DR concept Election of DR and DR DR DR oncept of DR and DR was introduce to provide representation of segment and to manage updates efficiently P3 DR DR P1 P0 Packets Hello is exchanged via IP multicast Highest priority is selected as DR by OSPF djacency with the segment is formed with DR and DR P2 P1 Highest priority elected

4 OSPF state process OSPF state process (cont.) / /24 E / /24 E1 OSPF State OSPF State Process Hello: I am router ID I don t see anyone Hello: Since I have ID I will start the exchange Down Init Hello: I am router ID and I see you 2-way Hello: I am router ID I can see you now Ex-start Hello: My ID is higher I will start the exchange Exchange Hello: Here is my LS database summary Loading Full Process Hello: Since I have ID I will start the exchange Hello: OK here is my LS database summary too OK LS cknowledge give me your complete network statement OK LS cknowledge thanks Down Init 2-way Ex-start Hello: My ID is higher I will start the exchange Exchange Hello: Here is my LS database summary Loading Thanks LS acknowledge Here it is Full Shortest path route selection Maintaining information / / /24 TDM FDDI ost = 6 ost = 1 ost = 10 omputer1 ost = /24 Link-State down Link state goes down DR Hello: Thanks, need to propagate the changes as well send LS update X 4 1 DR 2 Hello: Thanks for the LS update I will update my table Hello: ccording to topology table after processing the algorithm the best path is via I prefer highest cost to reach omputer1 Topology Table NET ost Out Interface To0 To0 Hello: Need to send LS update to DRs Notifies DRs via multicast address DR then notifies others (neighbors) via multicast address Hello: Need to send LS update to neighbor

5 Maintaining information (cont) Point-to-Point scenario heck LSD entry dd entry to LSD Send LS to DR Flood LS to neighbors Run SPF for the new routing table entry Same sequence number? ignore If higher update LSD NO, send LSU with new information Router send hello to detects its neighbors The concept of DR and DR is not followed, adjacency is automatic Just like broadcast networks the OSPF packets still uses multicast address NM topology OSPF with NM topology X.25 Frame Relay TM Non-broadcast Multi ccess (NM) topology allows a single router interface to interconnect multiple routers lthough NM supports interconnection of multiple routers it has no broadcast capability

6 NM = Frame-relay / TM topologies (cont.) NM = Frame-relay / TM topologies Full mesh In a typical NM topology sub-interface is used to interconnect routers The interface is split into several subinterface of normally called logical interfaces originating from a single physical interface. Partial mesh Sub-interface support multiple, point-topoint or point-to-multipoint connections Star (hub and spoke) DR and DR selection in NM Point-to-Multipoint mode NM topology in the selection of DR is considered like other broadcast media Full connectivity is required to perform the election of DR and DR between all other routers in the NM topology Neighbors must be listed and configured statically Partial mesh Star (hub and spoke) Start topology and partial-mesh is the usual topology for point-multipoint The concept of DR/DR election was not use in this topology and there is no requirements for static configuration for each neighbors

7 NM topology summary Written exercise 4! Mode Preferred Subnet ddress djacency RF or isco Please answer the attached worksheet material in your student manual NM Fully meshed Same Manual configuration DR/DR elected RF Objective roadcast Fully meshed Same utomatic No DR/DR isco To practice what you have learned Point-tomultipoint Partial mesh or star Same utomatic No DR/DR RF Written exercise 4 Different for each subinterface Point-topoint Partial mesh or star, using sub-interface utomatic No DR/DR isco OSPF operation in a single area! OSPF with internal routers roadcast network onfiguring OSPF in a Single rea S Point-to-Point network S Note: all configuration example commands are zebra/quagga base <Output Omitted> Interface Ethernet0 ip address /24 <Output Omitted> Interface Ethernet0 ip address /24 Interface Serial 0 ip address /30 router ospf network /24 area 0 network /30 area 0 router ospf network /30 area 0 network /24 area 0

8 Optional commands Optional commands cont. Router ID Interface Loopback0 <Output Omitted> Interface lo ip address /32 Interface eth0 ip address /24 router ospf router ID network /24 area 0 network /32 area 0 Router ID: Router active interface IP address containing the highest IP address Loopback interface: Highest IP address in the interface can be overridden by the loopback interface IP address and if several loopback interface is configured the highest IP address of any active loopback interface is used roadcast network S1 Point-to-Point network Non isco device ost OSPF command is normally configured to the router outgoing interface connecting to non-isco devices to allow inter-operability S0 router(config-if) # ip ospf cost cost OSPF over NM topology Note: The following examples are isco base NM mode configuration command router(config-if)# ip ospf network non-broadcast Point-to-multipoint mode command router(config-if)# ip ospf network point-to-multipoint [nonbroadcast]

9 OSPF over NM topology (cont.) NM broadcast mode command router(config-if)# ip ospf network broadcast Point-to-point mode command router(config-if)# ip ospf network point-to-point OSPF in NM mode Non-broadcast mode default, it needs the ip ospf network command ip ospf network broadcast neighbor statement is required neighbor ip-address [priority number][pollinterval sec][cost number] R1(config)# interface serial 0 R1(config-if)# ip address R1(config-if)# encapsulation frame-relay R1(config-if)# ip ospf network non-broadcast R1(config)# router ospf 1 R1(config-router)# network area 0 R1(config-router)# neighbor R1(config-router)# neighbor R1(config-router)# neighbor OSPF in Point-to-Multipoint mode OSPF in roadcast mode Point-to-Multipoint is normally used in a star topology and each connection is treated just like point-to-point NO election of DR/DR election is taking place R1(config)# interface serial 0 R1(config-if)# ip address R1(config-if)# encapsulation frame-relay R1(config-if)# ip ospf network point-to-multipoint R1(config)# router ospf 1 R1(config-router)# network area 0 In NM broadcast mode a full mesh topology is required for the automatic DR/DR election or manual election can also be done based on priority R1(config)# interface serial 0 R1(config-if)# ip address R1(config-if)# encapsulation frame-relay R1(config-if)# ip ospf network broadcast R1(config)# router ospf 1 R1(config-router)# network area 0

10 OSPF in Point-to-Point mode Sub-interface in the NM mode is treated as a physical point-to-point network by OSPF and the adjacency for such connection is automatic R1(config)# interface serial 0 R1(config-if)# no ip address R1(config-if)# encapsulation frame-relay R1(config)# interface serial0.1 point-to-point R1(config-subif)# ip address R1(config-subif)# frame-relay enterface-dlci 51 R1(config)# interface serial0.2 point-to-point R1(config-subif)# ip address R1(config-subif)# frame-relay enterface-dlci 52 R1(config)# router ospf 1 R1(config-router)# network area 0 Verifying OSPF Operation Note: all example verification commands are zebra/quagga base Verifying OSPF operation Verifying if OSPF is configure show ip protocol Verifying all routes learned by the router show ip route Verifying area ID adjacency show ip ospf interface Verifying OSPF operation (cont.) Verifying OSPF timers and statistics show ip ospf Verifying information about DR, DR and neighbors show ip ospf neighbor detail Verifying link-state database show ip ospf database

11 Verifying OSPF operation (cont.) learing the IP routing table entry clear ip route Displaying debug outputs from the router debug ospf <option> Lab exercise 3! Please perform the required configuration in the worksheet material of your student manual Objective To practice what you have learned Lab exercise 3 onfiguring OSPF in a single area! Questions?