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Enabling ISIS on a Cisco router

Ok, now that I have read over 250 pages of IS-IS, I finally get to the part about configuring IS-IS on the Cisco router.

I type:

R1(config)#router isis

R1(config)# The router prompt should change to config-router. It does not.

I don't get the correct prompt, should be


If I type router ?

I get the following options:

bgp, egp, eigrp, igrp, isis, iso-igrp, mobile, odr, ospf, rip, static.

When I try enabling ISIS on my 3620, everything works fine. Cannot enable ISIS on R1 or R2 but I can enable ISIS on R3. Any ideas?

On router R1 2610, my IOS is c2600-d-mz.122-6

On router R2 2620, my IOS is c2600-ik2s-mz.120-7.T

On router R3 3620, my IOS is c3620-p-mz.120-9

Any thoughts, PLEASE!

New Member

Re: Enabling ISIS on a Cisco router

The first code you posted does not support isis I could not find any info on the second but my guess is it also does not support isis.


Re: Enabling ISIS on a Cisco router

Wait - if the CISCO IOS code does not support a feature, why is the feature an option? Are you sure you understand the problem? Thank you for the response anyway.


Re: Enabling ISIS on a Cisco router

Thanks Drogell - you were correct!! but vague.

From Cisco:

The 3620 is running a Service Provider image.

R1 is running desktop and R2 is running IP Plus IPSEC 3DES.

IS-IS is only supported on the Enterprise, Service Provider, and Telco feature sets on the 2600 series.


New Member

Re: Enabling ISIS on a Cisco router

I had a similar problem a few months ago where I had a code that did not support ospf but if do a question mark at the config prompt it shows up. But if you do a search on the code it mentions tahat it does not support ospf. I agree cisco is vague.


Re: Enabling ISIS on a Cisco router

Thanks again for the help . . . I have downloaded IOS code for 2610-2613 enterprise plus, c2600-js-mz.120-8.bin and all is fine. Started configuring

IS-IS last night. I can give more details is anyone would like 'em.


New Member

Re: Enabling ISIS on a Cisco router

I Looked at this is one of my routers and I got this.

gw-2(config)#router isis ?

WORD ISO routing area tag

gw-2(config)#router isis


I would try and make sure that the code you are running supports isis.

I am running 120-12S on this router and it's the Service provider image.

This might be a good link

It is Cisco Feature Navigator it will tell you what the version of code that you are running supports.

Sorry I couldn't be of more help.