[c-nsp] static route to null0 not visible (BGP)

[Oliver Boehmer (oboehmer)]

Alex Foster <> wrote on Tuesday, July 04, 2006 6:39 PM:

> I have a couple of 3550s with already existing bgp sessions with some
> upstream providers and with iBGP running between them.  Im
> advertising a /24 at present and now want to advertise a /23 netblock
> in addition.  I 
> use static routes to null0 with metric of 254 for the existing /24 (on
> both routers) but when I add new routes to null0 for the /23, only one
> of my routers installs the route - the other learns the /23 via iBGP.
> If I remove the 254 metric on the offending router (and use the
> default 
> metric), the route is installed and advertised.  When the /23 is
> learned 
> by iBGP it has a metric of 200 so does this mean it is preferred over
> the static route ?? - If so why doesn't the /24 installed with a 254
> metric on both routers also behave this way.

Both the /23 and /24 should behave this way, i.e. one of the two routers
install the route as static and advertises it via BGP, the other will
learn the route via iBGP and will remove the floating static as the
static has a higher admin distance (254 vs. 200).
Not sure why your /24 doesn't behave this way, "show ip route 83.245.6.0
255.255.255.0" as well as "show ip bgp 83.245.6.0 255.255.255.0" would
help.. Maybe you learn the /24 via an IGP (OSPF) as well, so the OSPF
route wins over both the iBGP and the static route, so BGP will also
advertise the /24 on this router.

	oli