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Cisco 2611 routing issue

I am having a strange problem. For some reason my router is not using its route of last resort. I have a CISCO2611 using IOS (tm) C2600 Software (C2600-I-M), Version 12.2(8)T10, RELEASE SOFTWARE (fc1).

Here is the routes from the router.

Gateway of last resort is 172.29.222.234 to network 0.0.0.0

S 172.17.0.0/16 [1/0] via 172.16.128.81

C 172.16.0.0/16 is directly connected, FastEthernet0/0

172.29.0.0/16 is variably subnetted, 4 subnets, 3 masks

C 172.29.222.232/30 is directly connected, Serial0/0

C 172.29.223.252/32 is directly connected, Loopback0

C 172.29.3.0/24 is directly connected, FastEthernet0/0

C 172.29.242.252/30 is directly connected, BRI0/0

S* 0.0.0.0/0 [1/0] via 172.29.222.234

For some reason if I try to traceroute to a network with the first two octets being 172.29.X.X that is not a subnet on my router, it will not try the default route. If I try to get to any other network

not configured on my router it will use the default. I have other routers with the same configuration and they all work fine. Could this be an IOS bug? Any help is appreciated.

3 REPLIES
Cisco Employee

Re: Cisco 2611 routing issue

This is typical classfull behavior. Try configuring "ip classless" in global configuration mode.

It should take care of it.

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
New Member

Re: Cisco 2611 routing issue

Boy is my face red. I checked for that but overlooked that somebody put 'no' in front of the ip classless command. It is usually on by default. What are the advantages of turning ip classless off? Thanks for the help.

Cisco Employee

Re: Cisco 2611 routing issue

I don't really see any advantage of using the classfull mode. That is probably why the default behavior is now classless.

Harold Ritter
Sr. Technical Leader
CCIE 4168 (R&S, SP)
harold@cisco.com
México móvil: +52 1 55 8312 4915
Cisco México 
Paseo de la Reforma 222 Piso 19
Cuauhtémoc, Juárez
Ciudad de México, 06600
México
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