Student in need

Unanswered Question
Aug 13th, 2008
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Is this post in the correct section?


I am working with 5 2811 Cisco routers with fairly up-to-date software (not sure exactly what version). They are all connected to each other in a ring via serial cables. I am using RIP and a B-class network scheme; I am programming S0/0/0, S0/1/0 and FA0/0. When I program them, I can ping all serial ports when logged into any router. However, I can ping FA port (Ethernet) on the router I'm logged into but I can't ping any other FA port on any other router; or any host connected to ethernet portof the logged in router. I attached a .txt file with my programming. I REALLY need these routers to talk to the ethernet ports! It has been driving me nuts for weeks; my teachers can't help me but I can out-source (oddly enough)


Thanks in advance,

Ian S. Kocher




Edit: I forgot to add this

FA0/0 Changes with the router names

Central - 181.171.100.1

North - 181.171.110.1

South - 181.171.120.1

East - 181.171.130.1

West - 181.171.140.1


I'm doing it this way to indicate where the host is based on the IP Address.


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Richard Burts Wed, 08/13/2008 - 13:24
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Ian


This is a fairly common problem and not so difficult to fix. The problem is that all of the FastEthernets are configured as subnets in the same class B network and the serials are configured in different class B networks. One of the basic behaviors of RIP is that it automatically summarizes at network boundaries. So Central does not advertise 181.171.100.0 over its serial but advertises 181.171.0.0. And simmilarly North does not advertise 181.171.110.0 but advertises 181.171.0.0.


So no router has a route to the subnets of the FastEthernet on any other router.


There are a couple of ways that you might fix this.

- if you change the routing protocol and run RIPv2 or EIGRP there is a configuration option within the routing protocol for no auto-summary. This option tells the router to not summarize at network boundaries and will advertise the subnets of 181.171.0.0. Or run OSPF as the routing protocol since OSPF does not summarize by default.

- if you change the addressing scheme so that the serial links are also subnets of 181.171.0.0 then there would not be automatic summarization and all the routers would have routes to the other router subnets.

- if you change the addressing scheme so that the FastEthernet interfaces are each a unique class B network then summarization will not impact the advertisements and all routers will have routes to the FastEthernet of all other routers.


HTH


Rick

ianskocher Wed, 08/13/2008 - 13:36
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Rich,


Thanks for a quick reply. My skills as a router Jedi are limited; I have much to learn. Can you post an example of RIPv2's config option? I would much appreciate it!


Ian S. Kocher

Richard Burts Wed, 08/13/2008 - 13:43
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Ian


router rip

version 2

no auto-summary


HTH


Rick

ianskocher Wed, 08/13/2008 - 13:52
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Rich,


Sweet. That's a much simplified version of the examples I was looking at. I can't tell you how much better I feel. I can't wait to add that into the code as soon as I can get to the routers again.


Ian

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