Re: Routing Table Capacity At Cisco Router

There's a difference between the BGP RIB, the global RIB, and the FIB. The BGP RIB is all routes learned from all neighbors. On a route server it has an artificially large number of peers so that it's view is as diverse as possible. This is why you see the BGP RIB of 13 million routes.

All the "best" BGP routes then get promoted to the global RIB. The global RIB is what you see when you "show ip route". The FIB is then the combination of the global RIB plus other layer 2 information like next-hop layer 2 addresses, MPLS labels, etc. The FIB is what you see when you "show ip cef". When the platform says it supports X number of routes it's talking about the global RIB and FIB.

ASR 1K can surely hold the full Internet table with multiple views. Most of the "route-server.xyz.com" routers are 7200VXR, which is basically ASR 1K's precursor. Login to some of the route servers and "sh ver" and "sh mem".

With one or two views of the Internet table 1GB RAM is comfortable for holding the table and running most features you want. Keep in mind that the route-servers aren't running features. The only thing they do is host the BGP table so they don't even need extra RAM for packet forwarding features. It's basically just a control plane box.

HTH,

Brian McGahan, CCIE #8593 (R&S/SP/Security)
bmcgahan_at_INE.com
 
Internetwork Expert, Inc.
http://www.INE.com

On May 24, 2012, at 9:12 PM, "Mark Chandra" <mark.chandra_at_gmail.com> wrote:

> HI Guys,
>
> This is where I got the information :
>
>
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> route-views>show ip bgp summary
> 1. BGP router identifier 128.223.51.103, local AS number 6447
> 2. BGP table version is 2834042352, main routing table version 2834042352
> 3. 430131 network entries using 56777292 bytes of memory
> 4. 13237848 path entries using 688368096 bytes of memory
>
>
> So - third line tells me that curently 430131 best routes that are
> inserted into RIB, takes 56MB of memory. And whole BGP table from all
> neighbors takes 688MB right? And this router has learned 13milion
> routes/prefixes. If this is correct, then it's not so large amount.
> soft-reconfiguration however doubles the memory consumption and CEF also.
> I guess that router with 128MB of ram should be enough to hold 2 internet
> tables? in theory.
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>
>
> Regards
> Mark Stephanus Chandra - CCIE#23887
>
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> On 5/25/12 8:18 AM, "Alexander Halim" <cisco.alexand_at_gmail.com> wrote:
>
>> Interesting
>
>
> Blogs and organic groups at http://www.ccie.net
>
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Received on Thu May 24 2012 - 21:54:56 ART