North American Network Operators Group
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RE: router startup behavior

  • From: David Schwartz
  • Date: Mon Jan 14 15:35:05 2002 
On Mon, 14 Jan 2002 13:28:42 -0600, Steve Naslund wrote:

>Here is my best guess as to what you are seeing.  Most likely a large CIDR
>block is announced by a service provider A.  A small CIDR block is given to
>a customer who is connected to multiple service providers and thus running
>BGP.  Now the more specific route is announced by service provider B, he
>does not own the block but is announcing it on behalf of service provider As
>customer.  What is happening is that the customer has a line or router
>failure and that withdraws their more specific announcement from service
>provider B.  Since the service provider A is announcing a supernet route he
>now becomes the only route for that block.

	If that's the problem, a fix might be to not advertise any routes to a BGP 
peer until you receive all the routes that peer has to send you. I think it's 
elegant that when two routers connect, neither sends any routes to the other 
until each has received all the routes the other has to send. Very Zen, don't 
you think?

	DS