[c-nsp] Preventing IS-IS adjacencies over 1Q trunk

[Bruce Pinsky]

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Justin Shore wrote:
> I have a situation with IS-IS that's perplexing me.  I have a pair of 
> core routers connected via an etherchannel.  The etherchannel is also a 
> 1Q trunk.  The core routers have both routed connections to other 
> routers as well as common VLANs w/ HSRP for non-router devices.  My 
> intention was to build and IS-IS adjacency over the native VLAN on the 
> trunk.  However I noticed that both routers are building adjacencies 
> over 3 different VLANs that are permitted over that trunk.  All 3 SVIs 
> have IS-IS enabled on them.
> 
> I'm assuming that I probably shouldn't have IS-IS enabled on the SVIs 
> but is redistributing connected interfaces that appropriate solution? 
> I'm trying to eliminate as much redistribution as possible.  Is there a 
> better way to handle this?  I do need L2 between the chassis for the 
> non-routed links.
> 

If your IOS version supports it, you could use the "advertise-passive-only"
option in IS-IS.

http://tools.cisco.com/Support/CLILookup/cltSearchAction.do?Application_ID=CLT&IndexId=IOS&IndexOptionId=123&SearchPhrase=%22passive%22&Paging=25&ActionType=getCommandList&Bookmark=True

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bep

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