Chapter 6 IP Routing

Basic information When you configure interface of a node with IP and mask, the node will know the network corresponding to that IP and mask, so that it can reach all nodes in the same network. The node cannot reach another node in other networks without doing the following: For PCs define G.W For Routers define route

Routing Types Static routing (defined by administrator) Dynamic routing (protocols defined on router) Dynamic RoutingStatic Routing Easier to be implemented.Hard to be implemented in large and complex network. Requires no or simple knowledge in many cases. Requires knowledge about networks setup, both logical and physical. Less secure.More secure. Consumes CPU of routers and bandwidth. Does not consume CPU of routers and bandwidth.

ADRoute Source Default 0Connected interface 1Static route 90EIGRP 100IGRP 110OSPF 120RIP 170External EIGRP 255 (this route will never be used)Unknown

Router(config)#ip routing Router(config)#ip route Destination Mask NEXT HOP ADDRESS(0) AD permanent or MY EXIT INTERFACE(1) Router(config)#ip route Router(config)#ip route serial 0 Router(config)#ip route permanent Router(config)#ip route Static Routing / / / /24 f0.2 s0.1 s0/0.2 s0/1.1 f0/0.1

Default Route Router(config)#ip classless (enabled by default in versions 12.x) Router(config)#ip route Router(config)#ip default-network Viewing Information In CISCO Router Router#sh ip route Router#sh ip arp In PC C:\>route print C:\>arp -a

/ / / / / / / A1700B2600A B.2 f0.2 f0.1 s0.1 s1.1 s0/0.2 s0/0.2 s0.2 s0/1.1 f0/0.1 f0/0.1 e0.1 Setup #1: Contiguous (Classful)

/ / / / / / / A1700B2600A B.2 f0.2 f0.1 s0.1 s1.1 s0/0.2 s0/0.2 s0.2 s0/1.1 f0/0.1 f0/0.1 e0.1 Setup #2: Contiguous (Classless)

/ / / / / / / A1700B2600A B.2 f0.2 f0.1 s0.1 s1.1 s0/0.2 s0/0.2 s0.2 s0/1.1 f0/0.1 f0/0.1 e0.1 Setup #3: VLSM

/ / / / / / / A1700B2600A B.2 f0.2 f0.1 s0.1 s1.1 s0/0.2 s0/0.2 s0.2 s0/1.1 f0/0.1 f0/0.1 e0.1 Setup #4: Discontiguous

Interior Gateway Protocols IGP Ex terior Gateway Protocols EGP (Ex: Boarder Gateway Protocol BGP) Dynamic Routing Protocols IGP EGP To view Routed Protocols Router#sh protocols To view Routing Protocols Router#sh ip protocols Autonomous System 1Autonomous System 2

Interior Gateway Protocols Distance Vector: (RIP, IGRP) Link State (OSPF, IS-IS) Hybrid (EIGRP) Distance Vector Sends Full Route Table periodically, no matter there is update in routes or not. Distance Vector is associated with some problems, they are: Slow convergence. Inconsistence route (route by rumor). Route loop.

Routing Information Protocol (RIP) Open standard R.P Distance vector R.P Use simple metric = hop count Max hop count = 15 (16 is inaccessible) AD = 120 “R” in Route Table / / /24 Router(config)#router rip Router(config-router)#network Router(config-router)#network Router#clear ip route *

Redistribute Static / / / / /16 RB(config)#ip route RB(config)#router rip RB(config-router)#network RB(config-router)#network RB(config-router)#redstribute static RB.1.2 RA RC RD

Passive-Interface 2600B(config-router)#passive-interface s0/ / / / / / / / A1700B2600A B.2 f0.2 f0.1 s0.1 s1.1 s0/0.2 s0/0.2 s0.2 s0/1.1 f0/0.1 f0/0.1 e0.1

Debugging RIP Router#debug ip rip To debug remote (telnet) router you need to use the command: Router#terminal monitor Router#undebug ip rip Router#no debug ip rip Router#undebug all Router#no debug all

/ / / / / / / A1700B2600A B.2 f0.2 f0.1 s0.1 s1.1 s0/0.2 s0/0.2 s0.2 s0/1.1 f0/0.1 f0/0.1 e0.1 Setup #3: VLSM

/ / / / / / / A1700B2600A B.2 f0.2 f0.1 s0.1 s1.1 s0/0.2 s0/0.2 s0.2 s0/1.1 f0/0.1 f0/0.1 e0.1 Setup #4: Discontiguous

RIPv1 vs RIPv2 RIPv2RIPv1 Classless R.PClassful R.P Use multicast Use Broadcast in sending update Supports VLSM & DiscontiguousDoes not support VLSM & Discontiguous AuthenticationNo authentication Auto-summery can be disabled (ON by default) Auto-summery cannot be disabled To enable RIPv2 Router(config)#router rip Router(config-router)#version 2 To disable auto-summery in RIPv2 Router(config-router)#no auto-summery

RIPv1 vs RIPv2 Both versions have: Same metric and hop count Same AD Router(config-router)#distance Same number of paths to be load balanced (4 by default/ 6 maximum) Router(config-router)#maximum-paths 6 Same timers: Update interval: 30 sec. Invalid interval: 180 sec. (6*update) Holddown interval: 180 sec. (6*update) Flush interval: 240 sec. (8*update) Router(config-router)#timers basic

Interior Gateway Routing Protocol (IGRP) Cisco Prorietary R.P Distance vector R.P Classful R.P Cannot support VLSM & discontiguous networks AD = 100 “I” in Route Table Use composite metric (B.W, Reliability, Delay, Load, MTU) Inaccessible max metric is {(2^32)-1} or Max. hops 255 (100 by default) Used within one autonomous system (AS 1~65535) / / /24 Router(config)#router igrp 10 Router(config-router)#network Router(config-router)#network

IGRP timers: Update interval 90 sec. Invalid interval 270 sec. (3*update) Holddown interval 280 sec. (3*update+10) Flush interval 630 sec. (630*update) Router(config-router)#timers basic Router(config-router)#metric-maximum hops 255 Router(config-router)#maximum-paths 6 Router(config-router)#distance 100 Router(config-router)#redistribute static Router(config-router)#passive-interface

Debugging IGRP Router#debug ip igrp events Interior: Same AS, directly connected System: Same AS, indirectly connected Exterior: Other AS Router#debug ip igrp transactions Shows requests from neighbor routers and the broadcasts sent from your router.

Solutions to Distance Vector Problems Maximum Hop Count Split Horizon Route Poisoning Triggered Update