nanog mailing list archives

Re: useful bgp example


From: Dan White <dwhite () olp net>
Date: Wed, 19 May 2010 13:58:38 -0500

On 19/05/10 13:37 -0500, Jeff Harper wrote:
-----Original Message-----
From: Jared Mauch [mailto:jared () puck nether net]
Sent: Wednesday, May 19, 2010 1:29 PM
To: Jeff Harper
Cc: Deric Kwok; nanog () nanog org
Subject: Re: useful bgp example

Nice, but you don't show it as-path filtering your transits out.  I
frequently see people take something learned from transit A and
sending
it to transit B, and if it happens to be the backup path in-use for
your customer, your transits will accept it and likely pick you as
best-path and hairpin through your network.

- Jared

Yeah, I left out the actual prefix-list contents, in hindsight I should
have added it, so here it is. Also, a typo in the network statement,
lol.

network 1.1.1.0 mask 255.255.0.0

ip prefix-list NETZ description The networks we advertise via BGP
ip prefix-list NETZ seq 10 permit 1.1.1.0/16
ip prefix-list NETZ seq 1000 deny 0.0.0.0/0 le 32

You should be using 192.168.2.0 for documented examples,or at least private
space. Configs like this tend to get cut and pasted into routers and get
changed only when they don't work.

I just had to change a router config a couple of months ago that a consult
had set up using 11.0.0.0/24 and 12.0.0.0/24, for point to point links.

--
Dan White


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