BGP Paths

[oneciscokid]

I have three routers set up using BGP, and am curious about the command show ip bgp.

ISP1-------BIGISP-------ISP2

ISP1#show ip bgp
BGP table version is 11, local router ID is 210.210.210.1
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
*> 12.0.1.0/24 0.0.0.0 0 32768 i
*> 172.16.1.0/24 10.0.0.2 0 100 300 i
*> 172.31.1.0/24 0.0.0.0 0 32768 i
*> 192.168.0.0 10.0.0.2 0 0 100 i
*> 192.168.1.0 10.0.0.2 0 0 100 i
*> 210.210.210.0 0.0.0.0 0 32768 i

The Network 172.16.1.0/24, the path it takes is 100 then 300 then i, Why is the i there? I presume it means Internal, because it is an Internal network from ISP2. But why is it there? Isin't it an external network because you issue the command from ISP1. Same goes for the other networks in BIGISP as well, it goes to i.

12.0.1.0/24 - AS200 - ISP1
172.31.1.0/24 - AS200 - ISP1
210.210.210.0 - AS200 - ISP1

192.168.0.0 - AS100 - BIGISP
192.168.1.0 - AS100 - BIGISP

172.16.1.0/24 - AS300 - ISP2


TIA.

 

[KiscoKid]

i means IGP (interior gateway protocol)

Other attributes include:

e (the EGP protocol which BGP replaced)

? (INCOMPLETE meaning the prefix originated from some unknown source)

Origin is a well-known mandatory attribute thus the advertising AS tells its neighbors the origins of its routes.

As your routes are declared as IGP routes, I can only assume that the route in question has been cleanly derived in AS300 (through the use of the bgp "network" command)