Re: [nsp] CEF, BGP tables and memory

From: Basil Dolmatov (dol@office.east.ru)
Date: Sun Feb 11 2001 - 16:40:23 EST


On Sun, 11 Feb 2001, Jared Mauch wrote:

> Barry,
>
> Do you have dampening or soft-reconfiguration enabled on
> any of these peers?
>
> - jared
Oyeah... Any of these will eat all available memory from 128M even
without CEF... ;)

Nevertheless, Barry has got a point.
Router will contain BGP database with information about several possible
paths if available (and additional memory consumed for storing
history information for dampening or soft reconfiguration), but router
will have routing table with only one route for given address installed
(do not mention multiple-path-load-balancing, we all remember about it ;)
and there will be copy of _routing_table_ (not BGP paths table) in FIB
for CEF forwarding...

I can't recall whether CEF contains some memory optimizing features
like fast-switching, when entry in route-cache was created after first
packet forwarded to given destination (so unused routes in routing table
did not consume place in route-cache tables) or it just blindly creates
forwarding tree for CEF, including all possible routes installed in
routing table, whether they are used or not.

In any case one must carefully design routing plan instead of
putting more and more memory in the box, until it would be fed up
completely but still uncapable to handle all routes and features. ;)

Just my 0.02

Basil
>
> On Sun, Feb 11, 2001 at 12:26:50PM -0800, Barry Raveendran Greene wrote:
> >
> > Hi Miguel,
> >
> > I'm running CEF on several 7206s with 128MB with a few BGP views. In the
> > vast majority of cases, BGP's RIB will only send the single best path to the
> > FIB (used in CEF). So the entire BGP table is not copies to CEF.
> >
> > Barry
> >
> > > -----Original Message-----
> > > From: Miguel A.L. Paraz [mailto:map@internet.org.ph]
> > > Sent: Saturday, February 10, 2001 8:09 AM
> > > To: cisco-nsp@puck.nether.net
> > > Subject: [nsp] CEF, BGP tables and memory
> > >
> > >
> > > Hi,
> > >
> > > 128 MB RAM on my 7206 NPE-200 isn't enough to run CEF it seems, with two
> > > full BGP views. I don't think I need CEF for performance, but I do want
> > > CEF for uRPF.
> > >
> > > When you turn on "ip cef", I believe that copies the entire BGP
> > > table to CEF?
> > > I only need the customer static routes to copied to CEF, is that possible
> > > on 12.0.14(S) ?
> > >
> > >
> > >
> > > --
> > >
> > > http://www.internet.org.ph The Philippine Internet Resource
> > > Mobile Voice/Messaging: +63-917-810-9728
> > >
> > >
> > >
> > >
> > >
> > >
>
> --
> Jared Mauch | pgp key available via finger from jared@puck.nether.net
> clue++; | http://puck.nether.net/~jared/ My statements are only mine.
>
>



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