[c-nsp] route maps and bgp

[Pete Templin]

Gert Doering wrote:
> Hi,
> 
> On Tue, Oct 04, 2005 at 10:53:26AM +0200, Alexander Koch wrote:
> 
>>Be careful! Whenever you have BGP customers change that
>>please. A prefix-list is no good in that case, as when your
>>customer is not sending you his network range you will send
>>whatever is best in your routing table. Usually you then
>>'leak' that range from your transit (because it's best).
>>
>>BGP communities is the only sane thing to do here.
> 
> 
> I tend to disagree.  For a network that gets such basic things wrong, a
> configuration that errs on the side of *not* announcing things is 
> much better for everyone involved.

There might have been a misunderstanding here - what Alexander wrote is 
correct; if the customer stops announcing the prefix to <you> but you 
are still learning the prefix from <other-provider>, the prefix will 
match the prefix-list and <you> will provide transit from 
<other-provider> to <provider>.  Long story short, using only a prefix 
list means you will err on the side of over-announcing things.

BTDT, fixed my stuff, wear the t-shirt regularly.

pt