BFD for routes learned trough Route-servers in IXPs
nick at foobar.org
Wed Sep 16 09:04:13 UTC 2020
Ryan Hamel wrote on 16/09/2020 03:01:
> Install a route optimizer that constantly pings next hops
or if you want a more reliable IXP experience, don't install a route
optimiser and if you do, don't make it ping next-hops.
- you're not guaranteed that the icmp reply back to the route optimiser
will follow the forward path.
- you are guaranteed that icmp is heavily deprioritised on ixp routers
- the busier the IXP, the busier the control planes of all the IXP
routers you're going to ping, and the more likely they are to drop your
ping packets. This will lead to greater route churn. If this approach is
widely deployed it will lead to wider-scale routing oscillations due to
control plane mismanagement.
- route optimisers are associated with serious bgp leakage issues. if
you're doing this at an IXP, the danger is significantly magnified
because bi-lat peering sessions rarely, if ever, implement prefix filtering.
It is true that IXPs occasionally see forwarding plane failures. These
tend to be pretty unusual these days.
Be careful about optimising edge cases like this. You'll often end up
introducing new failure modes which may be more serious and which may
occur more regularly.
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