[j-nsp] Ideas on failure detection for a peering exchange shared between two routers.

[Dave Bell]

Advertise the routes to the rest of your network using next hop self. This
way the next hop is the loopback address of your routers, rather than the
peering LAN itself.

Regards,
Dave

On Tue, 2 Mar 2021 at 21:08, Jonathan Call <lordsith49 at hotmail.com> wrote:

> I've run into a corner case with a peering exchange that has me a little
> stumped for a solution that doesn't require redesigning the whole thing:
>
> Two MX80 routers participate in the same peering exchange. (A Primary and
> Secondary) Each has an interface configured in the same IP network within
> that IX. During a random bad event (maintenance error or fiber failure
> within the IX) the primary router loses access to everything on the IX
> network but it's link stays up. The secondary router is not impacted by the
> event. When this happens BGP on the primary router detects the loss of
> connectivity to its peers and updates all of its routes based on the BGP
> table from the secondary router. But because the peering link on the
> primary router is still UP/UP, the forwarding table says the next-hop is
> available via the bad interface. Here is an example of a Google route being
> learned on the IX:
>
> 34.84.0.0/14       *[BGP/170] 1d 02:06:40, MED 0, localpref 220, from
> 172.xx.xx.49
>                       AS path: 15169 I, validation-state: unverified
>                     > to 19x.xx.x.113 via xe-0/0/2.0
>
> Any way to work around this scenario?
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