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Cisco CCNA Test Tutorial: IGRP And Equal Expense Load Balancing

To go the CCNA Examination, you’ve obtained to grasp the part in the bandwidth command with IGRP and EIGRP and when to work with it. On this tutorial, we’ll configure IGRP over a frame relay hub-and-spoke network using the subsequent networks:

R1 (the hub), R2, and R3 are operating IGRP around the 172.twelve.123.0 /24 network. This can be a T1 line.

R1 and R3 can also be connected on a special subnet, 172.12.13.0 /24. The bandwidth of the relationship is 512 KBPS.

R2 and R3 can also be related by an Ethernet section, 172.23.0.0 /sixteen.

We’ll configure IGRP on R1, R2, and R3 Using the https://socialhattori.com/ router igrp one command. IGRP will run on all interfaces during the 172.12.0.0 and 172.23.0.0 network.

R1#conf t

R1(config)#router igrp 1

R1(config-router)#network 172.twelve.0.0

The one from the router igrp command refers to the Autonomous System (AS). IGRP is usually a classful routing protocol, so wildcard masks usually are not Employed in the community statements.

R2#conf t

R2(config-if)#router igrp 1

R2(config-router)#network 172.twelve.0.0

R2(config-router)#network 172.23.0.0

R3#conf t

R3(config-if)#router igrp 1

R3(config-router)#network 172.twelve.0.0

R3(config-router)#network 172.23.0.0

Run present ip route on R1. R1 will see 3 equivalent-cost paths towards the Ethernet community. IGRP supports load-sharing over as many as 4 equivalent-cost paths by default, so all three paths look in the routing table. R1 will even see a route to the loopback handle on R2 and two routes for the loopback handle on R3. (You can also operate demonstrate ip route igrp in order to see just the IGRP routes.)

R1#clearly show ip route igrp

I 172.23.0.0/sixteen [100/8576] through 172.twelve.123.2, 00:00:02, Serial0

[one hundred/8576] by using 172.12.thirteen.three, 00:00:02, Serial1

[one hundred/8576] by means of 172.12.123.3, 00:00:01, Serial0

Keep in mind that the figures during the brackets pursuing the community range from the routes are the executive Distance plus the IGRP metric, in that get.

Notice that classful masks are in use. IGRP does not assistance variable-duration subnet masks (VLSM).

There's two serial connections concerning R1 and R3. IGRP is assuming that both equally lines are T1 lines, jogging at 1544 KBPS. The 172.12.13.0 community is taking part in equivalent-Price load sharing due to IGRPs bandwidth assumption – that each one serial interfaces are linked to T1 lines.

To present IGRP a more accurate photo of your networks bandwidth, configure bandwidth 512 on R1 and R3s Serial1 interface (the interfaces about the 172.twelve.13.0 network).

R1(config)#interface serial1

R1(config-if)#bandwidth 512

R3(config)#interface serial 1

R3(config-if)#bandwidth 512

IGRPs assumption that every one serial lines operate at 1544 KBPS is overridden by the bandwidth 512 command. IGRP now thinks this line runs at 512 KBPS.

To begin to see the impact of the command, apparent your routing desk on R1.

R1#very clear ip route *

I 172.23.0.0/16 [one hundred/8576] by way of 172.12.123.three, 00:00:24, Serial0/0

[a hundred/8576] via 172.twelve.123.two, 00:00:17, Serial0/0

The routing table is cleared with crystal clear ip route *. To see only the routes received in IGRP updates as an alternative to the entire table, operate present ip route igrp.

Among the paths to 172.23.0.0 is now long gone – the route that went in the 172.12.thirteen.0 network. Now that IGRP sees that url as slower when compared to the Many others, equivalent-Price load balancing will never occur above the 172.12.thirteen.0 community.

Its important to understand that the bandwidth command will not in fact alter the bandwidth on the connection; it variations IGRPs assumption of exactly what the bandwidth is.

In the following part of this IGRP load-balancing tutorial, we’ll Check out how to configure unequal-Expense load balancing.