ISIS route summarization (it's a wrap)

Jack Bates jbates at
Tue Feb 24 13:28:59 UTC 2009

People were nice to point out that my memory does function correctly, 
but I did receive a single suggestion to spark the fire back to life in 
my brain. The suggestion was ISIS for infrastructure only, and iBGP for 
carrying all customer routes, which will lower the ISIS costs during a 
state change and give aggregation abilities at any level (useful for 
IPv4 primarily while we finish up adding IPv6).

Thanks for the help. Life slowly returns to normal in Lone Grove, OK, 
but it's amazing how much a tornado takes out of you; even when it 
doesn't take your IP network down.


Jack Bates wrote:
> In a level2 only ISIS network (not using multiple areas due to MPLS 
> limitations), is there a better method for handling aggregate routes 
> than creating an aggregate and redistributing it into ISIS for each 
> router? Primarily Cisco/Juniper based. Cisco I believe has an aggregate 
> option in ISIS (similar to OSPF) and Juniper has a separate aggregate 
> function which can be distributed into ISIS. Neither can do 
> summarization per say unless they cross between levels; unless I'm 
> mistaken.
> Offlist input is fine. Just trying to double check my brain while 
> setting up IPv6 on the access edges.
> Link state does have it's limitations. ;)
> -Jack

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