[c-nsp] full routing table / provider-class chassis

[Gert Doering]

Hi,

On Thu, Jun 11, 2009 at 03:57:11PM +0100, Ian MacKinnon wrote:
> > "XL" or "non-XL" has nothing to do with the number of *peers*.
> >
> > "XL" decides on the number of prefixes that you can have in your
> > forwarding table (hardware FIB) - and this will be about the same for
> > "1 peer with a full BGP Table" or "20 peers with the same set of
> > prefixes but just different BGP paths".
> >
> > A higher number of different "full table "peers is going to eat up CPU
> > memory and CPU power - memory is easy (Sup720-3CXL comes with 1Gbyte
> > RAM, which is sufficient for at least 10 "full table" BGP peers), but
> > CPU might reach its limit with 5 full table peers and 91 others.
> 
> I was the under the impression that the limit on these boxes 
> (and ASR1002 R1) was approx 1 Million routes.

True.  *FIB space* routes.

> I had assumed that was the total number of routes from all your peers, 
> eg we see about 280k routes in a full table, 

Correct.

> so that would be approx 4 full tables.

No.

1 full table has 280k routes.

100 full tables have 280k routes as well. (But LOTS of additional BGP path
information - but those are not stored in the FIB, and don't count for 
the "1 million" limit).

> Are you saying that the limit on the number of routes, is actually in 
> the FIB, ie active routes, so currently would always be about 280k, and 
> multiple full tables is OK.

BGP paths that don't go to the FIB are not "routes".  They are just prefixes
with path info.

(In other words: yes).

gert
-- 
USENET is *not* the non-clickable part of WWW!
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Gert Doering - Munich, Germany                             gert at greenie.muc.de
fax: +49-89-35655025                        gert at net.informatik.tu-muenchen.de
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