[j-nsp] Loop-free Alternate Paths for IS-IS Routes

Phil Bedard philxor at gmail.com
Wed Jan 13 09:51:13 EST 2010

It's new enough you probably won't find too many people with deployment experience outside of lab work.   It's something I looked at recently for OSPF and I think it's worth lab testing.   It's definitely easier to just turn on OSPF/IS-IS/LDP and forget it than maintain RSVP LSPs.  

http://www.juniper.net/us/en/community/junos/live/091103/  is a presentation given by Juniper and may answer some of the questions you have. 

There are topologies where it may not be able to find backup paths where MPLS FRR can, I think that's the biggest drawback.  There are ways to mitigate that concern with some static configuration, but you can't just turn it on and have it immediately replace RSVP.    Another potential large caveat is lack of SRLG information, if you have multiple WDM circuits riding the same fiber span.  


On Jan 13, 2010, at 1:48 AM, Stefan Fouant wrote:

> I'm wondering if anyone here has had any experience configuring the
> loop-free alternate paths for IS-IS in JUNOS, as described in the following
> drafts:
> - Internet draft draft-ietf-rtgwg-ipfrr-spec-base-12.txt, Basic
> Specification for IP Fast-Reroute: Loop-free Alternates 
> - Internet draft draft-ietf-rtgwg-ipfrr-framework-06.txt, IP Fast Reroute
> Framework
> And covered in
> http://www.juniper.net/techpubs/software/junos/junos95/swconfig-routing/jd0e
> 44501.html#jd0e44501.
> I'm looking for general guidance towards implementation, and any caveats
> which might be experienced in a typical deployment.  It seems to me that
> using this, we can entirely get rid of Fast Reroute, or Link/Node protection
> within RSVP/MPLS, but perhaps my understanding is a bit off.
> I'm also curious what experiences others have had with regards to
> troubleshooting backup paths that might be established as a result of a
> given failure.
> Thanks in advance!
> Stefan Fouant, CISSP, JNCIE-M/T
> www.shortestpathfirst.net
> GPG Key ID: 0xB5E3803D
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