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Configuring IGRPConfiguring basic IGRP is a two-step process. Configuring IGRP calls for the definition of an autonomous system (AS). By definition, an autonomous system is a set of routers under a single administrative technical authority. IGRP, EIGRP, and BGP all use the concept of autonomous systems, but BGP is the only routing protocol that actually utilizes the AS in routing decisions. It is not required to have a registered AS when configuring IGRP or EIGRP. This following two-step process can be followed by an optional third step to fine-tune IGRP to specific environments:
Example 10-1 illustrates the IGRP configuration from Figure 10-1. Example 10-1 IGRP Configuration! hostname igrp_rtr ! router igrp 2001 IGRP routing process network 172.16.0.0 Networks running IGRP network 172.18.0.0 network 206.191.241.0 ! ip classless ip default-network 206.191.241.0 Default Network ! Before moving on to configuring other IGRP options, let's take a look at the "Big D" and the "Big show" commands for IGRP. The "Big show" and "Big D" for IGRPTroubleshooting IGRP is similar to troubleshooting RIP. Most of the configuration errors around IGRP involve a bad network statement, discontinuous subnets, or inconsistent bit masks across the IGRP domain. The following is list of what I find to be the most useful show and debug commands for IGRP.
The sections that follow explain these commands in greater detail. show ip protocols [summary] CommandThis command displays all routing protocols, detailed timer and metric information, as well as routing update information. Example 10-2 lists the output of the show ip protocols command. Example 10-2 Output of the show ip protocols Commandigrp_rtr# show ip protocols Routing Protocol is "igrp 2001" AS number Sending updates every 90 seconds, next due in 19 seconds Update Timer Invalid after 270 seconds, hold down 280, flushed after 630 Other 3 timers Outgoing update filter list for all interfaces is Incoming update filter list for all interfaces is 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 Metrics IGRP maximum hopcount 100 IGRP maximum metric variance 1 Redistributing: igrp 2001 Routing for Networks: Networks IGRP is routing for 172.16.0.0 172.18.0.0 206.191.241.0 Routing Information Sources: Networks reporting routes Gateway Distance Last Update 172.18.1.55 100 00:00:29 206.191.241.42 100 00:00:06 172.18.1.7 100 00:01:06 172.16.2.4 100 00:38:38 172.16.1.1 100 00:50:01 Distance: (default is 100) Administrative Distance igrp_rtr# show ip route CommandThis command lists the router's current routing table and the one that it uses to make forwarding decisions. The output lists what routing protocol the route is from ”in this case, I for IGRP. The number behind the route is the administrative distance of the route followed by the composite metric of IGRP. The via field explains who the route is from, how long ago an update was received, and by what interface it was received. Example 10-3 lists the output of the show ip route command. In this example, the route 206.191.241.0/24 is the default route, marked by the *. It has an administrative distance of 100 and a composite metric of 1200. The IGRP neighbor informing the router about the route is 172.18.1.5. The last update about the route occurred 52 seconds ago, through the Ethernet 0 port. Example 10-3 show ip route Command Outputr7# show ip route Codes: C - connected, S - static, I - IGRP, R - RIP, M - mobile, B - BGP D - EIGRP, EX - EIGRP external, O - OSPF, IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 - OSPF NSSA external type 2 E1 - OSPF external type 1, E2 - OSPF external type 2, E - EGP i - IS-IS, L1 - IS-IS level-1, L2 - IS-IS level-2, * - candidate default U - per-user static route, o - ODR Gateway of last resort is 172.18.1.5 to network 206.191.241.0 I* 206.191.241.0/24 [100/1200] via 172.18.1.5, 00:00:52, Ethernet0 I 172.16.0.0/16 [100/1200] via 172.18.1.5, 00:00:53, Ethernet0 172.18.0.0/24 is subnetted, 3 subnets I 172.18.18.0 [100/1600] via 172.18.1.55, 00:00:29, Ethernet0 C 172.18.19.0 is directly connected, Loopback20 C 172.18.1.0 is directly connected, Ethernet0 r7# Router(config-router)#debug ip igrp [ transactions events ] CommandThe debug ip igrp transactions command shows detailed information about the routing updates being sent and received by the various interfaces. The debug ip igrp transactions command provides comprehensive routing detail, listing the networks and composite metric of each network. Both the commands show which interfaces are sending and receiving routes. The debug ip igrp events command provides only what type of routes are being advertised and received. Example 10-4 lists the output of the debug ip igrp transactions command, whereas Example 10-5 lists the output of debug ip igrp events. Use Figure 10-1 as reference for this output, which was performed on the igrp_router. Example 10-4 debug ip igrp transactions Command Output01:40:07: IGRP: received update from 206.191.241.42 on Ethernet0 01:40:07: network 172.16.0.0, metric 1121211 (neighbor 1121111) 01:40:27: IGRP: sending update to 255.255.255.255 via Ethernet0 (206.191.241.46) 01:40:27: network 172.16.0.0, metric=1100 01:40:27: network 172.18.0.0, metric=1100 01:40:27: IGRP: sending update to 255.255.255.255 via Ethernet1 (172.18.1.5) 01:40:27: network 172.16.0.0, metric=1100 01:40:27: exterior 206.191.241.0, metric=1100 01:40:27: IGRP: sending update to 255.255.255.255 via Ethernet3 (172.16.2.5) 01:40:27: subnet 172.16.1.0, metric=1100 01:40:27: network 172.18.0.0, metric=1100 01:40:27: exterior 206.191.241.0, metric=1100 01:40:27: IGRP: sending update to 255.255.255.255 via Ethernet5 (172.16.1.5) 01:40:27: subnet 172.16.2.0, metric=1100 01:40:27: network 172.18.0.0, metric=1100 01:40:27: exterior 206.191.241.0, metric=1100 igrp_rtr# Example 10-5 debug ip igrp events Command Output02:52:53: IGRP: sending update to 255.255.255.255 via Ethernet0 (206.191.241.46) 02:52:53: IGRP: Update contains 0 interior, 2 system, and 0 exterior routes. 02:52:53: IGRP: Total routes in update: 2 02:52:53: IGRP: sending update to 255.255.255.255 via Ethernet1 (172.18.1.5) 02:52:53: IGRP: Update contains 0 interior, 1 system, and 1 exterior routes. 02:52:53: IGRP: Total routes in update: 2 02:52:53: IGRP: sending update to 255.255.255.255 via Ethernet3 (172.16.2.5) 02:52:53: IGRP: Update contains 1 interior, 1 system, and 1 exterior routes. 02:52:53: IGRP: Total routes in update: 3 02:52:53: IGRP: sending update to 255.255.255.255 via Ethernet5 (172.16.1.5) 02:52:53: IGRP: Update contains 1 interior, 1 system, and 1 exterior routes. 02:52:53: IGRP: Total routes in update: 3 02:52:55: IGRP: received update from 172.18.1.7 on Ethernet1 02:52:55: IGRP: Update contains 1 interior, 0 system, and 0 exterior routes. 02:52:55: IGRP: Total routes in update: 1 |
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