[nsp] CEF routing bug?

[Ilker Temir]

> It looks like CEF creates the /32 adjacency based on the ARP irrespective
of
> whether or not its the correct route.

Wrong interpretation, CEF creates a /32 adjacency only if the entry is
directly connected. Adjacency is created when there is no IGP route in the
routing table.

Ilker

> The basic bug is that the route used is different based on whether or not
CEF is
> on and that seems to be a bug.
>
> Ilker Temir wrote:
>
> > If you lose the route from your IGP, the network will be directly
connected.
> > And CEF will create /32 adjacency based on ARP, as long as this spesific
> > adjacency exists it will be used even if the route is relearned from IGP
> > (since adjacency created from IGP will be less spesific).
> >
> > If arp times out, corresponding /32 CEF adjacency will be removed and
there
> > will be no problem. However arp will never time out in this case (unless
> > remote goes down). And to me, it is logical. Why would you want to
remove an
> > arp entry when the directly connected destination is still reachable ?
> >
> > Better change your design.
> >
> > Ilker
> >
> > ----- Original Message -----
> > From: "Ed Ravin" <eravin at panix.com>
> > To: <cisco-nsp at puck.nether.net>
> > Sent: Thursday, January 30, 2003 12:33 AM
> > Subject: [nsp] CEF routing bug?
> >
> > > Roy writes:
> > > > I have two routers ("A" and "B") and both are directly connected to
LAN
> > > > "C" ( a /26 subnet) [...]
> > > > For various reasons, I prefer the traffic on router "A" to go to LAN
"C"
> > > > via router "B".  I do this my entering more specific routes for LAN
"C"
> > > > pointing to router "B" (two route of /27).  This works fine until I
turn
> > > > on CEF.  When I do that, the direct connection is always used
instead of
> > > > the indirect routes.
> > >
> > > I'm seeing similiar problems on two different routers - a 7206 with
> > > 12.2(7c) and a 7513 with 12.0(21)S1.  On one router, routes received
> > > via OSPF or RIP do not override CEF when the CEF route is on a
> > > FastEthernet interface.  On the other router, the dynamic routes are
> > > used when the router is restarted, but if the dynamic routing
> > > protocol drops the route and CEF takes over, we can't lose the CEF
> > > route without rebooting the router again.
> > >
> > > _______________________________________________
> > >
>