Is Cisco 2821 with 512MB memory capable of handling full BGP routes?

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Jun 14th, 2010

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I have done some research online as well as on this forum. Some say yes and others say no. The posts were also couple of years old. I'm wondering if anyone are running full routes on the 2821 or have seen networks doing the same? Any input would be appreciated.

I have this problem too.
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Federico Coto F... Mon, 06/14/2010 - 11:45


I'm no BGP expert, but I've only seen full Internet routing table on some 7600s or higher.

I don't think you can do this with 2800s (or even 3800s)


jackawang Mon, 06/14/2010 - 12:05

Thanks for your reply, Federico.

That's was my initial thought also because all I've seen was 7200s and 7600's running BGP. But nowadays newer 2800 and 3800 routers are built so efficient that Cisco is stating it can run BGP without problem if it meets the memory requirement.  Unlike an ISP network, my setup will not become a transit of AS cloud. That makes think it might be possible running full routes on the existing 2821. I just wanted to see if anyone here have seen a similar setup running in production. Maybe it is just impossible.

Giuseppe Larosa Mon, 06/14/2010 - 12:24

Hello Jack,

memory is only  one component to build a router capable of receiving a full BGP table also a powerful CPU is needed or the device will stay with cpu at 100% for half an hour to all time in the worst case.

So even if a C2821 can have 512 MB of RAM it is not recommended to use it to receive 320,000 BGP routes.

Also the IOS code running on a C2821 has not been tested with full BGP tables leaving space to possible problems

You should go for a cisco 7200 with NPEG2 as a minimum with 2GB of RAM and much more powerful CPU

Hope to help


Latchum Naidu Mon, 06/14/2010 - 12:46

Hi Jack,

You got better suggestion from Giuseppe, this will help us in case you are in ISP end and doing some kind of BGP multihome and advertising public AS directly.

For me it seems that your 2811 routers connected to two ISP routers and pointing your default route to them is that correct?

And you are not advertising any public AS, am i right?

Though where the PE routers will face public AS traffic and advertise your private AS routes through their public AS

If that is the case then you can go for 2811 routers.

Because in my environment I am using only 1841 routers which are pointing to providers routes and advertising my networks and default route pointing to their gateway.



Latchum Naidu Mon, 06/14/2010 - 15:02

Hi Jack,

By seeing the diagram you are only advertising your private ASN /24 (your PA) to PE routers.

The PE devices will face full internet routing table/updates and public ASN routing capability.

PE routers will take away your ASN into internet and do the routing.

So you don't have any issues, you can go a head with 2811's.




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