[nsp] BGP backup transit link

[Steve Francis]

Look at BGP conditional advertisements.

Nick Kraal wrote:
> We have 2 transit links and running BGP and receiving about 110,000 prefixes
> from both providers. We are trying to use only one provider as our primary
> transit link and the other only when the first link is kaput.
> 
> This is as:
> 1. the primary link is actually 5x larger than the secondary (which was the
> old primary link before an upgrade). so we do see the secondary link
> bordering congestion. we have tried as_prepending at our upstream (up to 4x
> prepend -is this enough?) and inbound as_path filters restricting installing
> routes further than 3 as_hops away. we see that inbound traffic is the main
> culprit here -duh.
> 2. then this will then lead avoid a very obvious asymmetrical return route
> problem/issue -which in this part of the world can lead from jumps from 20ms
> to a sudden 300ms as traffic wants to return via the south pole.
> 
> Any ideas or is tweaking with as_prepends the only way we have. been looking
> at BGP link bandwidth but i think this is the secret recipe between two
> autonomous systems only.
> 
> Thanks in advance.
> 
> -nick/
> 
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