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Understanding the network.pdf - Back to Home

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Control commands:<br />

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RIP is an IGP, distance vec<strong>to</strong>r-based routing pro<strong>to</strong>col defined in RFC 1058. RIP uses<br />

a single routing metric—hop count—<strong>to</strong> determine <strong>the</strong> best route path. RIP, you may<br />

recall, has two versions: 1 and 2. The main differences are that version 1 uses UDP<br />

broadcasts and has no support for au<strong>the</strong>ntication and VLSM. RIP version 2 was<br />

added <strong>to</strong> Cisco IOS version 11.1, and it uses multicast for sending routing updates,<br />

as well as supports MD5 and text key au<strong>the</strong>ntication and VLSM. The IOS, by default,<br />

sends version 1 updates but will receive both version 1 and 2 updates. RIP's<br />

strength as a pro<strong>to</strong>col is that it is supported in some form by virtually every <strong>network</strong><br />

hardware vendor and operating system platform.<br />

In <strong>the</strong> previous example, RIP made <strong>the</strong> <strong>network</strong> announcements between <strong>the</strong> local<br />

Albany <strong>network</strong> and its ISP. The Albany <strong>network</strong> uses both classful and classless<br />

addressing, and since netmasks need <strong>to</strong> be sent in <strong>the</strong> update messages, RIP<br />

version 2 was required. You can force this in <strong>the</strong> configuration by using <strong>the</strong><br />

subcommand. Using <strong>the</strong> version command disables RIPv1<br />

support al<strong>to</strong>ge<strong>the</strong>r. Alternatively, if you need <strong>to</strong> support some legacy hardware that<br />

only speaks RIPv1, you can specify on each interface what message types <strong>to</strong><br />

support:<br />

asbr-a1(config)# interface e0<br />

asbr-a1(config-if)#ip rip send version 1 2<br />

asbr-a1(config-if)#ip rip receive version 2<br />

This configuration would only accept RIPv2 messages but send both v1 and v2<br />

updates. Let's examine <strong>the</strong> RIP configurations used on asbr-a1 and asbr-a2:<br />

asbr-a1#config t<br />

Enter configuration commands, one per line. End with CNTL/Z.<br />

asbr-a1(config)#router rip<br />

asbr-a1(config-router)#version 2

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