BGP Multihoming 2 providers full or partial?

Sun May 31 18:13:56 UTC 2015

Remember this:

1) for inbound traffic there will be no difference at all.

2) routers will ignore a static route if the link is down. If you can get
BFD from the providers then even better.

So you can emulate 99% of what you get with full routes by loading in
static routes. A simple example would be adding a 0.0.0.0/1 route to one
provider and 128.0.0.0/1 route to the other and get approximately 50% load
sharing.

You will still get redundancy as the route will ignored if the link is down
and traffic will follow the default route to the other transit provider.

If you find an offline source for IP ranges originated by each provider and
their peers, you can add routes for that to improve routing. Taking in
partial routes is also good if this provides you with a route count that
your routers can handle.

BGP shortest AS length routing is really not very good to begin with. If
you want the best routes, you need to analyse your traffic, sort by volume
or other metric and figure out which way is best for your top x AS
destinations.  It may be more work, but you will get better routing
compared to investing in expensive routers to take in full routes and then
hope BGP magic takes cares for the rest automatically.

Regards,

Baldur