BGP prefix filter list

Blake Hudson blake at
Mon May 20 14:14:58 UTC 2019

Baldur Norddahl wrote on 5/18/2019 3:57 AM:
> ...
> One router knows about 2 paths, the other about 4 paths. Why? Because 
> BGP only advertises the route that is in use. Everyone here of course 
> knows this, I am just pointing it out because culling information 
> before allowing it to be redistributed within your network is what BGP 
> is already doing anyway. It is possible to remove some of that 
> information from the local FIB too without losing anything at all.
> Using a default also gives you a dramatically shorter convergence time 
> if one of the transits goes down. Having 800k routes can be harmful to 
> your network even with equipment that can handle it. Yes I am aware 
> that I am not doing what I am preaching here, but I am considering it :-).

Thanks for the clarification. Yes, you are correct that each router will 
have its own unique view. By full view I meant that a router has at 
least one route for every prefix advertised into the DFZ. One should 
also expect that each transit provider will provide a slight variation 
in the routes provided via its "full BGP feed" because each transit 
provider has its own unique view and may include routes in its feeds 
that are not advertised into the DFZ.

Appreciate the discourse my friend,
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