[c-nsp] BGP Advertised Prefixes

[Jason Lixfeld]

max-prefix isn't an outbound mechanism, it's in inbound one.  Setting max prefix on a neighbor won't prevent it from announcing a zillion prefixes to that neighbor, it will only prevent that session from receiving a zillion prefixes from the neighbor where the max prefix setting is configured.

That detail output for Prefixes advertised has nothing to do with the total number of prefixes advertised to that neighbour at the time the command was run.  I think it just tells you how many prefixes it's announced throughout the lifetime of the session.   I think that number will increment anytime a prefix is added for whatever reason (downstream link flap, static route removal, whatever).

On 2013-04-09, at 4:27 PM, Ahmed Hilmy <hilmy.aa at gmail.com> wrote:

>  Hello Jason,
> thanks for your reply, i know that it clear but why this is happened, the filter has been set on both side identical.
> Kindly, find below log,
> # sh bgp neighbor x.x.x.x detail | i Prefix advertised
> 
>   Prefix advertised 2735, suppressed 0, withdrawn 1855, maximum limit 524288
> 
> #sh bgp neighbor  x.x.x.x advertised-routes
> 
> i count the number of advertised prefixes are only 215
> 
> Neighbor  x.x.x.x is my UP Link, Prefix list filter has been configured to allow a specific prefixes to be announced.
> 
> What do you think ?
> 
> 
> 
> On Tue, Apr 9, 2013 at 11:21 PM, Jason Lixfeld <jason at lixfeld.ca> wrote:
> The message is pretty clear.  x.x.x.x is announcing more prefixes than what your max prefix setting is configured for.  Either the uplink side is misconfigured or your max prefix setting is too small.
> 
> On 2013-04-09, at 4:13 PM, Ahmed Hilmy <hilmy.aa at gmail.com> wrote:
> 
> > Dear Friends,
> >
> > Recently i have faced a strange issue, BGP session with my UP Links goes
> > down due this log at UP Link side:
> > ---------------------------------------------------
> >
> > RP/0/RSP0/CPU0:Apr  8 13:10:54.818 : bgp[1044]: %ROUTING-BGP-4-MAXPFXEXCEED
> > : No. of IPv4 Unicast prefixes received from x.x.x.x: 401 exceed limit 400
> >
> > RP/0/RSP0/CPU0:Apr  8 13:10:54.818 : bgp[1044]: %ROUTING-BGP-5-ADJCHANGE :
> > neighbor x.x.x.x Down - Peer exceeding maximum prefix limit (CEASE
> > notification sent - maximum n           umber of prefixes reached) (VRF:
> > default)
> >
> >
> > -------------------------------------------------------------
> >
> > # sh bgp neighbor x.x.x.x detail | i Prefix advertised
> >
> >  Prefix advertised 2735, suppressed 0, withdrawn 1855, maximum limit 524288
> > #sh bgp neighbor  x.x.x.x advertised-routes
> >
> > i count the number of advertised prefixes are only 215
> >
> > So what Prefix advertised 2735 does it mean ?
> > Why i faced this issue with my UP Links , it happened sometime , if i have
> > configured BGP filter in wrong way so i have to face this
> > issue continuously.
> >
> > Any suggest plan to check ?
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