Deaggregation Disease

Richard A Steenbergen ras at
Fri Jul 21 18:55:16 UTC 2006

On Fri, Jul 21, 2006 at 01:59:35PM -0400, Jon Lewis wrote:
> As we push closer to the ipv4 route table limits of cisco's 6500/7600 
> series (with anything less than Sup720-3bxl), I suspect lots of networks 
> are going to be forced to start doing some sort of filtering of routes 
> beyond just refusing >24-bit networks or cisco's going to sell a lot more 
> Sup720-3bxl's, FAN2 trays, and power supplies in the next year or two.

It should be noted that the sup720-3a/3b tcam allocations (cef 
maximum-routes) only gives 190k of the 256k theoretical max to IPv6 routes 
by default. Anyone running a sup720 non-3bxl who has not manually adjusted 
those cef maximum-routes is either blowing up or about to blow up any day 
now, depending on how many internal routes they have and how much 
filtering their upstreams are doing.

Of course this isn't a new problem, many of us are still running old 
Foundry ironcore boxes with 700+ day uptimes and software so old it came 
with 120k or 140k default maximum routes. Similiarly, cam aggregation on 
such platforms (without enough cam to hold even close to enough routes for 
a full table) is nothing new either. Cisco could easily implement cam 
aggregation where they do not install a cef route entry if there is a 
covering less-specific route pointing to the same nexthop(s). It is 
hardly rocket science, and could extend the life of a 256k route tcam 
platform for many years to come. But clearly Cisco would rather just sell 
3bxl's. :)

Richard A Steenbergen <ras at>
GPG Key ID: 0xF8B12CBC (7535 7F59 8204 ED1F CC1C 53AF 4C41 5ECA F8B1 2CBC)

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