Using Route Servers

A couple of you have asked me how to check the Internet's BGP tables to see which ISP the Internet will send traffic to us through.

The answer is to use a route-server. These are usually Cisco or Juniper routers located at ISPs. They allow anyone to log in without a password and issue "show" commands. Each route-server has its own unique view of the Internet, and will accordingly show different routes that the others.

Here's a good list of route-servers. If you have the "telnet:" URL set up properly on your PC, clicking on a link will fire up your telnet program (PuTTY?) and connect to one of the servers.

Once on the server, just type "sho ip bgp regexp 11322". See below for additional useful commands. Here's a sample session:

.....................................................

.BBBBBB.................WW........WW..uu..uu.........Baden-

.BB...BB..........ll....WW........WW.................Wuerttembergs

.BB...BB.. eeee...ll.....WW......WW...uu..uu.........extended

.BBBBBB...ee..ee..ll.....ww..ww..ww...uu..uu.........

.BB...BB..eeeee...ll.....WW.WWWW.WW...uu..uu.........

.BB...BB..ee......ll......WWW..WWW....uu..uu.........

.BBBBBB....eeeee..lllll...WW....WW.....uuuu..........

.....................................................

BelWue-Cisco-Router Route-Server

cisco software Rel. 12.2

Konfiguration 1.47 erzeugt am 02/12/19 von merdian

01803/235638, ip@belwue.de





route-server>sho ip bgp regexp 11322

BGP table version is 2477141652, local router ID is 193.196.190.135

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal,

              r RIB-failure, S Stale

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          Next Hop            Metric LocPrf Weight Path

* i12.1.45.0/24     213.248.79.41            0    100      0 1299 7018 11322 i

* i206.24.119.0     213.248.79.41            0    100      0 1299 7018 11322 i

route-server>

This route-server, apparently in Germany, shows routes to both our prefixes via AS 7018, which is AT&T.

Here's another:

                   This system is the property of Energis



         Public access is allowed for the purpose of network management





route-server.as5388.net>sho ip bgp regexp 11322

BGP table version is 2234992752, local router ID is 195.92.201.108

Status codes: s suppressed, d damped, h history, * valid, > best, i - internal

Origin codes: i - IGP, e - EGP, ? - incomplete



   Network          Next Hop            Metric LocPrf Weight Path

*>i12.1.45.0/24     195.92.201.149          90    100      0 5511 3561 11322 i

* i                 195.92.201.150          90    100      0 5511 3561 11322 i

*>i206.24.119.0     195.92.201.149          90    100      0 5511 3561 11322 i

* i                 195.92.201.150          90    100      0 5511 3561 11322 i

route-server.as5388.net>

This one would route to AS11322, which is us, via AS3561, which is Savvis.

You shold always see a route or a set of routes for each of our two prefixes. The prefix (which means the network number, such as 12.1.45.0/24) is on the left, and the "AS PATH" is on the right.

Note: is it asked that you never type "sho ip bgp" by itself without qualifiers because that would be abusing the router, asking it to show all routes on the Internet. Always use qualifiers to cut down on the output, as I did above.

Other useful commands

Here are some other commands to try. Let's assume your AS is 6666.

sho ip bgp regexp 6666
Shows any path to or through your AS.
sho ip bgp regexp 6666$
Shows any path to your AS. Use this to make sure there is a path to each prefix in your AS.
sho ip bgp regexp 6666.+
Shows those ASPATHs where your AS is not at the end. Use this to make sure your AS is not being advertised as a transit AS.
sho ip bgp regexp [1111|2222] 6666$
Shows paths to your AS only if through either AS1111 or AS2222
sho ip bgp damp para
Shows dampening parameters on this router, if any.
sho ip bgp dampening flap regexp 6666
Shows whether this router thinks your route has been flapping.
sho ip bgp damp damp | incl 6666
Lists your AS if it has been damped.