[c-nsp] Cat7600/Sup720 and IPv4 vs IPv6 performance

Łukasz Bromirski lukasz at bromirski.net
Thu May 7 18:24:58 EDT 2009

On 2009-05-07 23:52, Rick Ernst wrote:
> The specs for the Sup720/3BXL indicate support for 1,000,000 IPv4
> routes and 400Mpps. The numbers drop in half for IPv6 (500K
> routes,200Mpps)

Yep, assuming you're doing either IPv4 or IPv6, not both at the same

> I can't find information on how the routing/capacity is partitioned.
> If I run IPv6 are my combined IPv4 and IPv6 table limited to 500K
> routes?  Can I carve out the memory so I can support a combination
> like 500K IPv4 routes and 250K IPv6 routes?  Will the platform mix
> and match v4 and v6 in the same chunk of memory?  Same/similar
> question for a combined IPv4/IPv6 platform; if I run both protocols
> is the aggregate traffic limited by the IPv6 specs?

The 6500 PFCs and DFCs TCAMs can be partitioned to support IPv4, MPLS,
IP multicast and IPv6. The IPv4 and MPLS entries take 72 bits, the
IP mutlicast and IPv6 entries take two entries - thus 144 bits are
needed. TCAMs have to be statically configured to serve this, so
after changing the allocation you have to reload the box.

For current settings you can check 'sh mls cef maximum-routes'
which will show (among other things):

FIB TCAM maximum routes :
Current :-
IPv4 + MPLS         - 512k (default)
IPv6 + IP Multicast - 256k (default)

To change the scheme to be able to fit more IPv4 or IPv6 routes you
can do a 'mls cef maximum-routes ip | ipv6' (and other options),
but if You're allocating more for IPv6 you will loose capacity for
IPv4 and vice versa.

> I don't know much more about IPv6 than how it is spelled, and I need
> to start hitting the books for it.  I've seen the IPv4 BGP table grow
> from less than 100,000 routes 10 years ago to almost 300,000 routes
> now, but don't have the same feel for IPv6.  I'm trying to get an
> idea of expected lifetime/capacity when deploying new equipment.

If you're looking for edge BGP peering router, you should look at
ASR 1k series, not 6500 which is positioned as a switch for enterprises.

"Don't expect me to cry for all the     |               Łukasz Bromirski
  reasons you had to die" -- Kurt Cobain |    http://lukasz.bromirski.net

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