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Cisco CCNA Examination Tutorial: IGRP And Equal Value Load Balancing
To pass the CCNA Examination, you’ve acquired to learn the purpose in the bandwidth command with IGRP and EIGRP and when to utilize it. With this tutorial, we’ll configure IGRP more than a body relay hub-and-spoke community making use of the following networks:
R1 (the hub), R2, and R3 are functioning IGRP about the 172.12.123.0 /24 community. This can be a T1 line.
R1 and R3 may also be related on a distinct subnet, 172.12.thirteen.0 /24. The bandwidth of the link is 512 KBPS.
R2 and R3 are also connected by an Ethernet section, 172.23.0.0 /sixteen.
We’ll configure IGRP on R1, R2, and R3 With all the router igrp 1 command. IGRP will run on all interfaces during the 172.twelve.0.0 and 172.23.0.0 network.
R1#conf t
R1(config)#router igrp one
R1(config-router)#community 172.twelve.0.0
The 1 during the router igrp command refers back to the Autonomous Technique (AS). IGRP is actually a classful routing protocol, so wildcard masks are usually not Utilized in the community statements.
R2#conf t
R2(config-if)#router igrp one
R2(config-router)#network 172.twelve.0.0
R2(config-router)#community 172.23.0.0
R3#conf t
R3(config-if)#router igrp 1
R3(config-router)#network 172.12.0.0
R3(config-router)#network 172.23.0.0
Run clearly show ip route on R1. R1 will see three equivalent-Charge paths on the Ethernet network. IGRP supports load-sharing around up to 4 equivalent-Price paths by default, so all 3 paths show up while in the routing table. R1 may even see a path to the loopback address on R2 and two routes for the loopback address on R3. (You may as well operate exhibit ip route igrp to be able to see just the IGRP routes.)
R1#display ip route igrp
I 172.23.0.0/sixteen [a hundred/8576] by using 172.12.123.two, 00:00:02, Serial0
[100/8576] by means of 172.12.13.3, 00:00:02, Serial1
[100/8576] by using 172.twelve.123.three, 00:00:01, Serial0
Bear in mind the figures while in the brackets following the network quantity within the routes are the executive Distance and also the IGRP metric, in that purchase.
Be aware that classful masks are in use. IGRP won't assistance variable-size subnet masks (VLSM).
There are two serial connections in between R1 and R3. IGRP is assuming that equally strains are T1 traces, jogging at 1544 KBPS. The 172.12.13.0 community is participating in equivalent-Price tag load sharing due to IGRPs bandwidth assumption – that all serial interfaces are linked to T1 lines.
To present IGRP a more exact image from the networks bandwidth, configure bandwidth 512 on R1 and R3s Serial1 interface (the interfaces around the 172.twelve.thirteen.0 community).
R1(config)#interface serial1
R1(config-if)#bandwidth 512
R3(config)#interface serial one
R3(config-if)#bandwidth 512
IGRPs assumption that every one serial lines operate at 1544 KBPS is overridden because of the bandwidth 512 command. IGRP now believes this line operates at 512 KBPS.
To see the effect of this command, distinct your routing desk on R1.
R1#clear ip route *
I 172.23.0.0/16 [a hundred/8576] through 172.twelve.123.3, 00:00:24, Serial0/0
[a hundred/8576] by way of 172.12.123.2, 00:00:seventeen, Serial0/0
The routing desk is cleared with apparent ip route *. To view just the routes been given in IGRP updates in lieu of the entire desk, operate demonstrate ip route igrp.
One of the paths to 172.23.0.0 is currently long gone – the route https://socialhattori.com/ that went in the 172.12.thirteen.0 community. Now that IGRP sees that website link as slower than the Many others, equivalent-Value load balancing will not likely take place around the 172.twelve.thirteen.0 network.
Its essential to know that the bandwidth command will not essentially change the bandwidth on the relationship; it changes IGRPs assumption of exactly what the bandwidth is.
In another portion of this IGRP load-balancing tutorial, we’ll Have a look at the way to configure unequal-cost load balancing.