"2M today, 10M with no change in technology"? An informal survey.

William Herrin herrin-nanog at dirtside.com
Tue Aug 28 19:11:52 UTC 2007

On 8/27/07, Deepak Jain <deepak at ai.net> wrote:
> an MSFC2 can
> hold 256,000 entries in its FIB of which 12,000 are reserved for
> Multicast. I do not know if the 12,000 can be set to serve the general
> purpose.
> The MSFC2 therefore can server 244,000 routes without uRPF turned on.

I'm hit square on with this because I use Sup2's with the msfc2/pfc2
for the link to both of my transit providers. I took this up with the
Cisco TAC overnight to find out where I stand. Here's what I found:

1. The msfc2/pfc2 does in fact have a limit that starts at 244,000 routes.

2. Once the limit is reached, excess routes will fail over to software
switching. TAC did not specify how routes are designated as excess.

3. The Sup 720 (except for the 3bxl) has a similar limit, however the
"mls cef maximum-routes" command can be used to make upwards of
260,000 TCAM entries available to IPv4 unicast routing. The Sup 2 does
not support this command.

4. The suggested upgrade path is the Supervisor 720-3BXL whose TCAM
can support up to 1M IPv4 FIB entries or 500k IPv6 FIB entries. With a
7600 (instead of a 6500) the RSP 720-3CXL can do the same and also has
a faster processor, more memory, etc.

Now, my request for help:

I have a leaf node on the DFZ handled by a pair of Sup2's
(pfc2/msfc2), two transit providers and several peers. My focus is
very heavily domestic, and I'd like to delay my upgrade. I'd like to
buy some time by aggregating the incoming APNIC region prefixes
(http://www.iana.org/assignments/ipv4-address-space) into the
following FIB entries:

Can anyone suggest how to program that into the router or refer me to
the URL of the correct documentation at Cisco's site?

Thanks in advance,
Bill Herrin

William D. Herrin                  herrin at dirtside.com  bill at herrin.us
3005 Crane Dr.                        Web: <http://bill.herrin.us/>
Falls Church, VA 22042-3004

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