IP Training Programme. Module 1: IP Generic Session 3: IP Services

Transcription

1 IP Training Programme Module 1: IP Generic Session 3: IP Services

2 Subjects Review The IP Address continued Routing protocols (Concept) Firewalll and NAT DNS server and DNS operation concept DHCP server including options Network security in general

3 SMALL REVIEW FROM SESSION 1 AND 2 Just the important stuff

4 IP Classes Class Purpose First byte between Subnet mask Prefix Max hosts A Unicast 0 and / B Unicast 128 and / C Unicast 192 and / Additional classes Class Purpose First byte between Subnet mask Prefix Max hosts D Multicast 224 and 239 None special None - E Reserved 239 and 255 None None -

5 Between logical net Router 1 Net: /24 WAN link Net: / Router

6 TCP/IP vs. ISO TCP/IP was developed with four layers.

7 TCP in IP in Ethernet 6 Byte 6 Byte 2 Byte Ethernet data 46 Byte to 1500 Bytes Destination MAC address Ethernet frame Containing IP Packet IP packet (Simplified) 32 bit Source IP Address Source MAC Address 32 bit Destination IP Address Type Protocol IP packet Contains the value 800 showing the Ethernet frame contains an IP packet Data in IP packet. Variable size TCP Packet Frame Check (Checksum CRC) Contains the value 6 indicating the IP packet contains a TCP packet TCP packet (Simplified) Sequence number Data in TCP packet. Variable size Session layer related information Session layer part of TCP (Simplified) Source port Destination Port TCP Data

8 TCP and UDP TCP builds virtual connections between end points. (hosts) Connection oriented protocol Create, maintain and close Reliable transport. The transmitter splits data segments. (Ethernet maximum 1500 bytes data) The receiver assemble the data segments. The receiver acknowledges the reception of segments. Lost segments are retransmitted. UDP transports data between end points. (hosts) Connection less. Just send data and hoping the receiver is on-line. Unreliable transport. (No guarantee the data is delivered) The receiver do not assemble the data segments. No flow control No error control or recovery

9 6: Get the web-page Local DNS server 2. root DNS server 3.no DNS server 5 1 Internet 4 ascom.no DNS Server Client 6 Web server The local DNS server will normally be a caching DNS server meaning it will remember what it learns reducing traffic and decreasing respond time. All information has a time-to-live. The information will be deleted when time-to-live expires.

10 THE IP ADDRESS CONTINUED Beyond the original IP classess A, B and C

11 Classfull IP addresses The original classfull divided the unicast space in three fixed classes IP address shortage because of internet growth as early as 1993 Class First byte between Subnet mask Prefix Max hosts Networks A 0 and / B 128 and / C 192 and / Prefix Subnet mask - decimal Subnet mask - binary / / /

12 Network and broadcast Two IP addresses of each logical network is reserved for special purposes. They are illegal as host IP addresses All host bits 0 is the logical network name All host bits 1 is the local broadcast IP address For example the ,100.0/24 network is the network name is the broadcast address Usable IP address ranges from to A total of 254 usable addresses

13 Boson subnet calculator

14 Subnetting Classfull IP addresses Network part Host part For example: /16 Network part Host part: 4.5 Classless IP addresses Network part Subnet part Host part For example /24 Network part: Host part: 5

15 Classless IP addresses Subnettet class B network as /24 One class B net subnettet to 256 subnets Network Subnet mask Max hosts

16 Exponentiation Mathematical operation Called potens in Swedish, Norwegian and Danish. 2 5 = 2 ^ 5 = 2 * 2 * 2 * 2 * 2 = = 7 ^ 2 = 7 * 7 = = 2 ^ 64 = Often used when dealing with numeric systems.

17 Numeric systems II *10^0 = 7*1 = 7 6*10^1 = 6*10 = 60 3*10^2 = 3*100 = 300 8*10^3 = 8*1000 = 8000 Decimal sum = *2^0 = 1*1 = 1 0*2^1 = 0*2 = 0 1*2^2 = 1*4 = 4 1*2^3 = 1*8 = 8 Decimal sum = 13

18 The binary byte *2^0 = 1*1 = 1 1*2^1 = 1*2 = 2 1*2^2 = 1*4 = 4 1*2^3 = 1*8 = 8 1*2^4 = 1*16 = 16 1*2^5 = 1*32 = 32 1*2^6 = 1*64 = 64 1*2^7 = 1*128 = 128 Decimal sum = 255

19 The binary byte *2^0 = 1*1 = 0 0*2^1 = 1*2 = 0 0*2^2 = 1*4 = 0 1*2^3 = 1*8 = 8 1*2^4 = 1*16 = 16 1*2^5 = 1*32 = 32 1*2^6 = 1*64 = 64 1*2^7 = 1*128 = 128 Decimal sum = 248

20 Classless IP addresses To adapt the size of a logical network to customer networks the classes were abandoned. Subnets is logical networks prefix Subnet mask Subnets Max hosts / / / / / / /

21 Classless IP addresses A binary 1 in the subnet mask means the bit belongs to the logical network or subnet A binary 0 in the subnet mask means the bit belongs to the host part of the IP address Prefix Subnet mask - decimal Subnet mask - binary / / / / / / /

22 ROUTING PROTOCOLS

23 The route table The route table is used by all hosts including Routers. a list of all logical networks known by the host. Used to decide in which direction packets should be send. The route table contains Destination network Direction Distance

24 The road sign Destination, Direction and Distance

25 Route tables on routers I am on the /24 network The destination network for the ping packets is /24 Routertable R2 NETWORK SEND TO / / / Routertable R3 NETWORK SEND TO I will send the pakets to my default gateway / / / Routertable R1 NETWORK SEND TO / / / Routertable R4 NETWORK SEND TO / / /

26 Route tables on routers Routertable R2 NETWORK SEND TO I received a packet for My routetable has an entry that says traffic to /24 should be sent to / / / Routertable R3 NETWORK SEND TO / / / Routertable R1 NETWORK SEND TO / / / Routertable R4 NETWORK SEND TO / / /

27 Route tables on routers Routertable R2 NETWORK I received a packet for My routetable has an entry that says traffic to /24 should be sent to the connected /24 network SEND TO / / / Routertable R3 NETWORK SEND TO / / / Routertable R1 NETWORK SEND TO / / / Routertable R4 NETWORK SEND TO / / /

28 Route tables on routers Routertable R2 NETWORK SEND TO / / / Routertable R3 NETWORK SEND TO / / / Routertable R1 NETWORK SEND TO I received a ping packet from / I will respond with a pong packet / is on another logical network / so I will send the packet to my default gateway Routertable R4 NETWORK SEND TO / / /

29 Route table creation The route table in routers can be created and maintained in two ways 1: Static route table entry Entries are entered manually 2: Dynamic route table entry Entries are sent between routers automatically Require the use of a Routing protocol such as RIP, OSPF, IS-IS or BGP

30 Static routes Static vs. dynamic Routes entered manually by administrators Routes changed manually by administrators Time consuming and error prone Dynamic routes Routes automatically entered by a routing protocol. Routes automatically changed by a routing protocol.

31 Routing protocols A Routing Protocol is a protocol that exchanges routing information between routers. A router receives routing information from other routers and learn their logical networks. Popular routing protocols RIP, OSPF, BGP,EIGRP,IS-IS

32 RIP RIP Routing Information Protocol is a popular routing protocol. Measures distance in HOP s HOP s is equal to numbers of routers on the way to the distant logical network. RIP is a Distance Vector Routing protocol Distance = Number of HOP s to destination network Vector = Direction of destination network. (Which neighbor to send packets to)

33 R1, R2 and R3 just booted R4 swithced off Route table R / / / NETWORK NETWORK Route table SEND TO R3 HOP / / / X Route table When a Router NETWORK is booted SEND it TOwill know HOP only the IP / / connected to /30 its physical ports. 1 addresses and subnet masks of the logical networks It will also know it is using the routing protocol RIP. R1 It has been configured by a technician.

34 RIP RIP will transmit its Routing table to its neighbor routers every 30. seconds. The neighbors will learn the transmitting routers logical networks. The neighbors will transmit their routing tables so the local router learns their logical networks.

35 R1 updates R2 R2 receives a copy of R1 route table and insert it into its own routing table Route table R / / / / / / R1 Route table R / / / X Route table R / / /

36 A logical network can only have one entry in the routing table /30 is represented twice. One with a HOP count of 1 and one with a HOP count of 2 Two /30? Route table R / / / / / / R1 Route table R / / / X Route table R / / /

37 Shortest HOP count chosen The best route to a destination network is the route with the lowest number of HOP s Route table R / / / / / R1 Route table R / / / X Route table R / / /

38 R1 updates R3 R1 also updates the neighbor R3. R3 learns R1 s network. Route table R / / / / / Route table R3 R 1 X / / / / / Route table R / / /

39 R2 updates R3 Route table R / / / / / Route table R3 X / / / / / / Route table R / / /

40 All routers updatet Route table R / / / / / / Route table R3 X / / / / / / Route table R / / / / / /

41 R4 the Default Gateway switchet on Route table R / / / / / / R4 is a little special as it is holds the Default Route to the internet. It is statically configured by a technician in this case. Route table R / / / / / / Route table R / / / / / / Route table R / /

42 Convergence! Everybody knows everybody Route table R / / / / / / / Route table R / / / / / / / R3 updates R4. R4 updates R3 which updates R1 and R2 Route table R / / / / / / / Route table R / / / / / / /

43 RIP - Technically Maximum HOP-Count = 15 Network diameter should be below 15 routers HOP-Count = 16 means network unreachable RIP exist in two versions Version 1 Uses broadcast and only allow classfull IP networks Version 2 Uses multicast and allows classless IP networks

44 When changes occurs WAN line Down Route tabel R / / / / / / / Route tabel R3 X / / / / / / / Route tabel R / / / / / / / Route tabel R / / / / / / /

45 R1 and R3 detect change Neighbor unreachable Route tabel R / / / / / / / Route tabel R3 X / / / / / / / Route tabel R / / / / / / / Route tabel R / / / / / / /

46 New routes installed in route table Route tabel R / / / / / / / Route tabel R3 X / / / / / / / Route tabel R / / / / / / / Route tabel R / / / / / / /

47 What happens when WAN works again? Route tabel R / / / / / / / Route tabel R3 X / / / / / / / Route tabel R / / / / / / / Route tabel R / / / / / / /

48 It returns to shortest HOP count at the next updates among the routers Route tabel R / / / / / / / Route tabel R / / / / / / / Route tabel R / / / / / / / Route tabel R / / / / / / /

49 Routing protocols Routing protocols keep the routing tables up-to-date in the routers. Routing protocols like RIP are used in small companies. OSPF and EIGRP are used in enterprises. The Internet uses BGP as a worldwide routing protocols keeping track of to routes.

50 Firewalls and NAT NAT: Network Address Translation D-Link Wireless Broadband Router Power M1 M2 WAN WLAN LINK/ACT Speed 10/100M DI-614+

51 Power M1 M2 WAN WLAN LINK/ACT Speed 10/100M ADSL physical D-Link Wireless Broadband Router DI-614+ Internettet ADSL Modem Bolig

52 ADSL logical Home / ADSL Router with NAT / / BBRAS / / Home Home Internet provider Home

53 Small home Router /24 1 Inside F I R E W A L L Outside /30 BBRAS 10 DHCP Clients 103 Home DHCP Server and N A T SOHO Router DHCP Client Internet provider DHCP Server Internet provider

54 NAT translation private IP addresses NAT: Network Address Translation -one to one IP address translation Translates IP addresses from inside to outside network Private IP adresses allocated to be used behind NAT / to / to / to NAT hides the inside network (LAN) from the outside

55 NAT tabel NAT table on the router Inside net: /24 1 WAN address Outside net: /32 Internet SOHO Router with NAT Inside network NAT table Outside network Protocol From To Protocol From To

56 NAT tabel Dynamic NAT table Data TCP From IP to IP WAN address Outside net: /32 Internet Inside net: /24 SOHO Router with NAT Protocol TCP Inside network NAT NAT tabel table Outside network From To Protocol From To

57 NAT tabel NAT table From inside to outside IP address From IP Data TCP To IP WAN address Outside net: /32 Data TCP From IP To IP Inside net: /24 SOHO Router With NAT Internet Protocol TCP Inside Indre network NAT NAT tabel table Outside Ydre network From To Protocol TCP From To

58 NAT tabel NAT table Return packets Data TCP From IP To IP WAN adsress Outside net: /32 Data TCP From IP To IP Inside net: /24 SOHO Router with NAT Internet Protocol TCP Inside Indre network NAT NAT tabel table Outside Ydre network From To Protocol TCP From To

59 NAT and PAT TCP and UDP uses port numbers. NAT/PAT software keeps track on connections using: - Protocol ( eg. TCP) - Inside from IP ( eg ) - Inside from port ( eg. Port 1152) - Out side to IP ( eg ) - Out side to port ( eg. port 80) The five parameters describe a unique connection

60 NAT tabel NAT and PAT Data From port 1152 To port 80 T C P From IP Inside net: /24 To IP SOHO Router with NAT and PAT WAN address Outside net: /32 Data From port 1152 To port 80 T C P From IP To IP Internet Protocol TCP Inside Indre network NAT NAT tabel table Outside Ydre network From :1152 To :80 Protocol TCP From :1152 To :80 Portnumber

61 NAT tabel PAT finds unused Port Data From port 1152 To port 80 T C P From IP Inside net: / To IP SOHO Router with NAT and PAT WAN address Ydre net: /32 Data From port 2345 To port 80 T C P From IP To IP Internet Protocol TCP Inside Indre network NAT NAT tabel table Outside Ydre network From :1152 To :80 Protocol TCP From :1152 To :80 TCP : :80 TCP : :80 Unused port on outside found

62 NAT tabel PAT sikrer korrekt levering Data From port 80 To port 1152 T C P From IP Inside net: / To IP SOHO Router with NAT and PAT WAN adresse Outside net: /32 Data From port 80 To port 2345 T C P From IP To IP Internet Protocol TCP Inside Indre network NAT NAT tabel table Outside Ydre network From :1152 To :80 Protocol TCP From :1152 To :80 TCP : :80 TCP : :80

63 NAT tabel Always unique ports Important if for example two browser windows connect to same server Data From port 80 To port 1153 T C P From IP Inside net: / To IP SOHO Router with NAT and PAT WAN address Outside net: /32 Data From port 80 To port 1153 T C P From IP To IP Internet Protocol TCP Inside Indre network NAT NAT tabel table Outside Ydre network From :1152 To :80 Protocol TCP From :1152 To :80 TCP : :80 TCP : :80 TCP : :80 TCP : :80

64 DNS SERVER Roles and functions

65 DNS server roles Master DNS server Administrate DNS zones For example: ascom.se Slave DNS server Receives zone information from master server Acts as redundant server and ofloads the master Caching DNS server Caches (stores) information learnt Flushes information when TTL Time to Live - expires

66 Company example DHCP Client DHCP Client DNS Configuration: is DNS.ASCOM.Se is Forward unknown requests to Net: / Router/ Firewall 4 WEB server DNS Server DHCP Server Internet DNS server DHCP Configuration: Ip address scope: to Subnet mask: DNS server: Default gateway:

67 DNS zone records A - Address record An A-record is used to give a host a name For example Default nslookup type=a

68 DNS zone records SOA - Start Of Authority record Name and mail address on the authority of the domain

69 DNS zone records NS - Name Server record Shows DNS servers for the domain. The order of the servers are Changed for each reply for Allowing load sharing to the DNS servers.

70 MX Mail exchange DNS zone records Shows Mail servers for the domain. The ascom.se domain has two mail servers Mail.ascom.se and mail.ascom.nl The mailserver with lowest preference has highest priority and will be used first. If unreachable the next lowest preference is tried. The IP address of the mail server(s) is found using a A- record lookup

71 Windows DNS Server Windows server version 2003, 2008 and 2012 has intutive DNS server management tools. mail.mydomain.com A record points to A record points to mail.mydomain.com MX record (preference=10) mail.myotherdomain.dk MX record (preference=20)

72 DHCP SERVER Server 1 DNS DHCP Server 2 FIL PRINT Client Printer Client Client Client DHCP 254 DHCP DHCP 2 SW1 DHCP SW2 SW3 1 Building / /24 1 R /30 DHCP R2 5 Building /30 6 R3 Building 3 Internet

73 DHCP Client DHCP Client DHCP example DHCP lease pool on server: IP address range: Subnet mask: DNS server: Default gateway: Net: /24 3 ROUTER Internet DHCP Server Static IP address DHCP Client 1. DHCP-Discover 2. DHCP-Offer DHCP Server(s) 3. DHCP-Request DNS server DHCP-Ack Network

74 DHCP server The DHCP Discover packet is a broadcast and is limited to OSI layer 2. Blocked by Routers Professional routers can function as DHCP-relays relaying the DHCP packets from a physical network to the DHCP server

75 DHCP Relay one server many logical networks Server 1 DNS DHCP Server 2 FIL PRINT Client Printer Client Client Client DHCP 254 DHCP DHCP 2 SW1 DHCP SW2 SW3 1 Building / /24 1 R /30 DHCP R2 5 Building /30 6 R3 Building 3 Internet DHCP relay configured is on on router Router interfaces facing the DHCP clients to forward incoming. DHCP packets to

76 DHCP options DHCP options is information the DHCP clients needs beside the IP Address and the subnet mask. DHCP options examples Option 003: IP Address of default gateway Option 015: IP Address of DNS server(s) Option 150: IP Address of TFTP server Trival File Transfer Protocol Option 042: IP Address of NTP server Network Time Protocol

77 DHCP options Windows DHCP server options configuration example TFTP servers are often used to store IP phones configuration files.

78 4 5 GHI JKL 7 8 PQRS TUV # CISCO IP PHONE 7960 messages services directories settings 4 5 GHI JKL 7 8 PQRS TUV # CISCO IP PHONE 7960 messages services directories settings Configuring IP phones IP Telephone DHCP Client DHCP Client IP Telephone DHCP Client DHCP Client 1 2 ABC 3 DEF 6 MNO i 1 2 ABC 3 DEF 6 MNO i * 0 OPER 9 WXYZ * 0 OPER 9 WXYZ 1 Router/ Firewall Net: / Internet DNS server FTP server IP Telephone server DHCP Server DHCP Configuration: Ip address scope: to Subnet mask: DNS server: Default gateway: Option 150 (TFTP)

79 Thank you for listening