Routing Protocol Configuration and Review

This section highlights the basic router commands necessary to add the RIP and IGRP to a router configuration.

RIP

Table 10.7 lists the configuration commands necessary to enable RIP on a router.

Table 10.7. RIP Configuration Commands

Task	Router Command
Enter global configuration mode	RouterA#configure terminal
Enter RIP configuration mode	RouterA (config)#router rip
Configure network 172.16.0.0 to be advertised	RouterA (config-router)#network 172.16.0.0
Exit configuration mode	RouterA (config-router)#<CTRL>Z

The show IP protocol command displays detailed information about each IP routing protocol that has been configured on the router.

The following output displays the results of the show IP protocol command after RIP has been configured:

 RouterA#show ip protocol Routing Protocol is "rip"   Sending updates every 30 seconds, next due in 2 seconds   Invalid after 180 seconds, hold down 180, flushed after 240   Outgoing update filter list for all interfaces is not set   Incoming update filter list for all interfaces is not set   Redistributing: rip   Default version control: send version 1, receive any version     Interface        Send  Recv   Key-chain     Ethernet0        1     1      2     Loopback0        1     1      2     Serial0          1     1      2   Routing for Networks:     172.16.0.0   Routing Information Sources:     Gateway         Distance      Last Update     172.16.24.252        120      00:00:12   Distance: (default is 120) RouterA# 

By default, RIP sends updates every 30 seconds. Also, the RIP hold-down timer is set to 180 seconds, and a neighbor router has an IP address of 172.16.24.252.

IGRP

Table 10.8 lists the configuration commands necessary to enable IGRP on a router.

Table 10.8. Configuring IGRP

Task	Router Syntax
Enter global configuration mode	RouterA#configure terminal
Enter IGRP routing protocol configuration mode for autonomous system 1	RouterA(config)#router igrp 1
Configure network 172.16.0.0 to be advertised	RouterA(config-router)#network 172.16.0.0
Exit configuration mode	RouterA (config-router)#<CTRL>Z

The following output displays the results of the show IP protocol command after IGRP has been configured.

 RouterA#show ip protocol Routing Protocol is "igrp 1"  Sending updates every 90 seconds  , next due in 7 seconds   Invalid after 270 seconds, hold down 280, flushed after 630   Outgoing update filter list for all interfaces is not set   Incoming update filter list for all interfaces is not set   Default networks flagged in outgoing updates   Default networks accepted from incoming updates   IGRP metric weight K1=1, K2=0, K3=1, K4=0, K5=0  IGRP maximum hopcount 100  IGRP maximum metric variance 1   Redistributing: igrp 1   Routing for Networks:     172.16.0.0   Routing Information Sources:  Gateway  Distance      Last Update  172.16.24.252  100      00:00:15   Distance: (default is 100) RouterA# 

By default, IGRP sends updates every 90 seconds. Also, the IGRP maximum hop count is set to 100, and a neighbor router has an IP address of 172.16.24.252.

The next section of this chapter covers access lists for IP and IPX traffic. Access lists allow network administrators to restrict access to certain networks, devices, and services. They provide an effective means of applying security within an organization; they also permit or deny specific types of traffic to pass through an interface. The types of IP traffic they filter can be based on source or destination address or address range, protocol, precedence, type of service, icmp-type, icmp-code, icmp-message, igmp-type, port, or state of the TCP connection. A full list of access lists is provided in Table 10.9.

Table 10.9. Types of access lists.

Numeric Range	Description
1 through 99	IP standard access list
100 through 199	IP extended access list
200 through 299	Ethernet access list
300 through 399	DECnet access list
600 through 699	AppleTalk access list
700 through 799	48-bit media access control (MAC) address access list
800 through 899	IPX standard access list
900 through 999	IPX extended access list
1000 through 1099	Service Access Point (SAP) access list

Access lists provide a powerful set of tools that can deny and permit users to access specific applications or hosts . The tradeoff for using access lists, however, is that they require processing power to compare packets entering or exiting an interface with the entries in the list.

A wide variety of access lists can be applied to a router interface. This chapter focuses only on the IP standard and extended access lists, IPX SAP access lists, and IPX standard and extended access lists.