Sybex CCENT Chapter 8: IP Routing Instructor & Todd Lammle

Chapter 8 Objectives Understanding IP routing Static routing Dynamic routing –RIP –RIPv2 –Verifying routing 2

To route a router need to know: –Remote Networks –Neighbor Routers –All Possible routes to remote network –The absolute best route to all remote networks –Maintain and verify the routing information What is Routing? CB A D

Basic Path Selection What interface will the router send out a packet if it has destination address of ?

Simple IP Routing

Routing/PDU Example: Host A Web browses to the HTTP Server….

Routing/PDU Example 2

ICMP Error example

Basic Routing Using MAC and IP Addresses

Testing basic routing Knowledge

Configuring IP Routing Network

ip route remote network [mask] {address|interface} [distance] [permanent] Router(config)#ip route remote_network mask next_hop Static Route Configuration

ip route or ip route s0 Static Route Example SO B A B Stub Network SO

Default Routes SO B A B Stub Network SO ip route ip classless

Configuring a gateway of Last resort

Routing protocols are used between routers to: –Determine the path of a packet through a network –Maintain routing tables –Examples? Routed protocols are: –Assigned to an interface –Once the path is determined by the Routing protocol, determines method of delivery –Examples? Routing vs. Routed

Autonomous System 1Autonomous System 2 IGPs: RIP, IGRP EGPs: BGP Routing Protocols An autonomous system is a collection of networks under a common administrative domain. IGPs operate within an autonomous system. EGPs connect different autonomous systems.

Classful Routing Overview Classful routing protocols do not include the subnet mask with the route advertisement. –Within the same network, consistency of the subnet masks is assumed. –Summary routes are exchanged between foreign networks. –Examples of classful routing protocols: RIP Version 1 (RIPv1) IGRP

Classless Routing Overview Classless routing protocols include the subnet mask with the route advertisement. –Classless routing protocols support variable-length subnet masking (VLSM). –Summary routes can be manually controlled within the network. –Examples of classless routing protocols: RIP Version 2 (RIPv2) EIGRP OSPF IS-IS

IGRP Administrative Distance=100 Router D Router B Router A Router C RIP Administrative Distance=120 Default Administrative Distance Directly Connected: 0 Static Route: 1 RIP: 120 IGRP: 100 EIGRP: 90 OSPF: 110 Administrative Distance

CB A D Routing Table Routing Table Routing Table Routing Table Routing Table Routing Table Routing Table Routing Table Distance—How far Vector—In which direction Distance vector algorithms do not allow a router to know the exact topology of an internetwork. All routers just broadcast their entire routing table out all active interfaces on periodic time intervals Distance Vector

Pinhole Congestion

Discovering Routes

Converged Routes

Routing Loops

64kbps T1 –Hop count metric selects the path, 16 is unreachable –Full route table broadcast every 30 seconds –Load balance maximum of 6 equal cost paths (default = 4) –RIPv2 supports VLSM and Discontiguous networks RIP Overview

Router(config)#router rip Router(config-router)#network network-number* network network router RIP network network router RIP *Network is a classful network address. Every device on network uses the same subnet mask RIP Routing Configuration

RIP Routing Example 2

RIP Version 2 Allows the use of variable length subnet masks (VLSM) by sending subnet mask information with each route update Distance Vector – same AD, and timers. Easy configuration, just add the command “version 2” under the router rip configuration router rip network version 2

Discontiguous Addressing Two networks of the same classful networks are separated by a different network address / / /24 –RIPv1 and IGRP do not advertise subnet masks, and therefore cannot support discontiguous subnets. –OSPF, EIGRP, and RIPv2 can advertise subnet masks, and therefore can support discontiguous subnets.

A Discontiguous network

Verifying RIP Router#show ip protocols Router#show ip route Router#debug ip rip Router#undebug all (un all)

Summary –Open your books and go through all the written labs and the review questions. –Review the answers in class. 33