route converge time

Daniel Corbe dcorbe at
Sat Nov 21 15:17:22 UTC 2015

Baldur Norddahl <baldur.norddahl at> writes:

> Hi
> I added a default static route to provider A on router A and did
> the same to provider B on router B. This is supposed to be a trick that
> allows the network to move packets before everything is fully converged.
> Traffic might not leave the most optimal link, but it will be
> delivered.

The other thing here is the one of the main advantages of taking a full
routing table is so that you can be free of default routes.

> Anyone got any tricks or pointers to what can be done to optimize the
> downtime in case of a IP transit link failure? Or the related case of one
> my routers going down or the link between them going down (the traffic
> would go a non-direct way instead if the direct link is down).

With only two providers, route convergence is always going to be a
painful process.  Especially if you're still using old equipment on your

But you shouldn't be losing transit links often enough for it to be a
major problem for your users.  If you are, I'd start looking at other
options for transit.

You could also take smaller tables from a wider variety of providers.
Most folks in the wholesale transit business offer default routing and
customer specifics.  This won't give you best path selection in the
truest sense but if you're connected to enough upstream providers it can
get you pretty close.

And if you're a content consumer rather than a content provider, go and
peer with anyone that has an open peering policy.  Most important
content providers will peer with anyone that services customer and have
relatively flexible traffic minimums.  Off the top of my head that's
facebook, google, netflix, yahoo, microsoft and several others.

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