Re: ASN to prefix list

[Michael Douglas <Michael.Douglas () IEEE org>]

If you know Cisco IOS at all you could query a public route server for
whatever command output you could want.  Easily scriptable with expect.

This project maintains a bunch of routers with open CLI access for show
commands, and full internet BGP tables from multiple providers:
http://www.routeviews.org/

Typically one would use a regex for the AS number & AS path.

route-views>sh ip bgp | inc ?
  LINE  Regular Expression

show ip bgp | inc _701$  <-this gives you all the prefixes originated with
AS 701 (UUNet) at the end of the AS path.

I'm not sure what it is you're trying to accomplish, or if this would even
be an appropriate method.  AS path filtration can get pretty complex on the
internet. Customers may have their own AS number "C" behind their ISP "B".
And ISP "A" may be in front of ISP "B" in the AS path.

A B C <-AS path.  Depending on with AS you want to see prefixes from, which
could be multiple ones, the regex syntax is going to be different.

_B_ <- prefixes transiting AS B
_C$ <- prefixes originating from AS C; which would be a subset of what is
transiting B

This goes into the syntax and issues with BGP AS path filtration with
regex: http://blog.ine.com/tag/as-path/

Actually, the robtex swiss army knife might be a lot easier to use, but
it's web based.

http://www.robtex.com/  AS701 example http://as.robtex.com/as701.html

Regards,

michael.douglas<at>ieee.org

ccie #26817 || cissp-issap #69713

_______________________________________________
Pauldotcom mailing list
Pauldotcom () mail pauldotcom com
http://mail.pauldotcom.com/cgi-bin/mailman/listinfo/pauldotcom
Main Web Site: http://pauldotcom.com