[c-nsp] How many maximum routes does Cisco 2900 router support?

Adam Greene maillist at webjogger.net
Fri Jan 8 09:23:52 EST 2016

Our 2921 with a full routing table, 2GB RAM, and around 60M aggregate
throughput hovers around 40-50% CPU utilization, with occasional higher
spikes. When we were pushing >100M aggregate through it, the CPU was
regularly spiking to near 100%.

We have another one with multiple BGP sessions, 512MB RAM, but only a few
actual routes. However, we are also running QoS policies on it, including
NBAR. When aggregate throughput gets up near 100M, CPU tends to spike above


-----Original Message-----
From: cisco-nsp [mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of
Robert Hass
Sent: Thursday, January 7, 2016 9:20 AM
To: Patrick M. Hausen <hausen at punkt.de>
Cc: Try Chhay <try.chhay at gmail.com>; cisco-nsp at puck.nether.net
Subject: Re: [c-nsp] How many maximum routes does Cisco 2900 router support?

On Thu, Jan 7, 2016 at 9:00 AM, Patrick M. Hausen <hausen at punkt.de> wrote:

> > However, I suspect CPU resources and route convergence time would be
> more of the limiting factor than absolute route count.
> We've been running IPv4 full tables with two 3825 for a couple of 
> years. 1 GB of RAM, which is AFAIK the maximum this platform supports. 
> Switched them for 6500 just a little over a year ago.

It depends what more you have on this 2901. Programming FIB, RIB,
calculating routing is CPU consuming operation. With 2.5GB RAM I don't have
problems putting 1MLN IPv4 routes even in C2901.

If you're looking for small, cheap BGP router for 100Mbps/s link - 2901 is
OK. But be prepared that configuration should be minimum - no NAT, no IPSEC

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