BGP Path Filtering

Joe Abley jabley at
Sat May 17 15:30:47 UTC 2003

On Friday, May 16, 2003, at 23:58 Canada/Eastern, Sean Donelan wrote:

> Are you suggesting that its a bad idea to make things appear "too 
> easy,"
> and by suggesting more complex configs we'll scare off the bottom rung
> of network engineers.  Maybe.

Not really; I'm suggesting that a few more minutes worth of thinking at 
day one will save many more minutes of pain down the road.

> Barry Greene's & Philip Smith's book "Cisco ISP Essentials: A
> comprehensive guide to the best common practices for Internet service
> providers" uses static prefix filters almost exclusively in all of its
> example "best practices" for ISPs.  Although the ISP book is a useful
> reference for network engineers at any size network, the examples
> work best for networks of a certain size.

And presumably for networks which never expect to grow. In my 
experience the networks that don't grow are also the ones that shrivel 
and die.

I think that the message "community strings are hard" (like its friends 
"BGP is hard" and "let's turn on RIP") need to stop propagating. It is 
just not that difficult to do things right the first time, and you 
don't need to be a bigger network than a pair of 2501s with a small 
handful of external BGP sessions to see the benefit of it.


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