[c-nsp] IOS XR filter route from OSPF?

[Aaron]

Are you running BFD on the link as well?

On Thu, Nov 30, 2023 at 8:33 AM Drew Weaver via cisco-nsp <
cisco-nsp at puck.nether.net> wrote:

> Can you point me towards a hint on how you implement import/export filters
> in OSPF on IOS XR?
>
> Are you referring to 'distribute lists'?
>
> Another thing that is a bit quirky from my standpoint is why when the
> remote router gets knocked offline BFD on the OSPF process doesn't kill the
> route immediately.
>
> It seems like it takes 15-20 seconds for the route to be removed entirely
> from OSPF from when the transport goes down.
>
> Thanks,
> -Drew
>
>
>
>
> -----Original Message-----
> From: cisco-nsp <cisco-nsp-bounces at puck.nether.net> On Behalf Of Mark
> Tinka via cisco-nsp
> Sent: Tuesday, November 28, 2023 10:34 AM
> To: cisco-nsp at puck.nether.net
> Subject: Re: [c-nsp] IOS XR filter route from OSPF?
>
>
>
> On 11/28/23 17:02, Nick Hilliard via cisco-nsp wrote:
>
> >
> > prefix filtering is a defining feature of a policy routing protocol.
> > OSPF is a link-state protocol, and doesn't support the concept of
> > having different visibility of prefixes inside the same area.  If you
> > want that with OSPF, you'll need to divide your network into different
> > areas, which is messy. Probably better off using bgp for this.
>
> Filtering in link state routing protocols is a bit of a misnomer,
> technically speaking... but, you can use import/export filters on routers
> with OSPF and IS-IS.
>
> It would not necessarily limit the LSA/LSP flooding scope, but you end up
> with the desired outcome (all manner of caveats apply).
>
> All that said, the usefulness of an IGP is in its homogeneous view of the
> network from and by all participating nodes. Bad things can happen when one
> partitions IGP's, especially in an unintended way. As you say, BGP is
> better for this kind of thing, as typically, IGP's should carry
> infrastructure prefixes, and you don't really want to filter those as they
> provide basic router-to-router connectivity.
>
> Mark.
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