6 Replies Latest reply: Apr 4, 2012 5:29 PM by riedmueller RSS

    show ip bgp "i" in AS path? but its eBGP...

    Stephen

      Hey guys,

       

      Just reading the Wendell Odom 642-902 book and come accross the following table:

      eBGPwtf.jpg

       

      He states that all routes learned in the table are eBGP routes because there is no i in the 3rd column.  Not too sure what he means by this, however, my question is; if all these routes are eBGP, then what does the "i" mean in the Path column (on the far right hand side)?

       

      Regards,

      Stephen

        • 1. Re: show ip bgp "i" in AS path? but its eBGP...
          Brian

          The "i" in the path column as in the below example:

           

          I3_1#sh ip bgp

          BGP table version is 4, local router ID is 3.3.3.3

          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

          *> 128.107.0.0      192.168.1.5              0             0 11 i

          *> 172.20.0.0       0.0.0.0                  0         32768 i

          *> 172.30.0.0       0.0.0.0                  0         32768 i

          I3_1#

           

          relates to the "Origin codes" above in RED.  Key thing to note, i = IGP does not stand for Internal Gateway Protocol nor does e = EGP stand for External BGP.  The "e = EGP" stand for the old EGP protocol which has not been used since 12.3 or there abouts and you should not see this in use today.  The "i = IGP" stands for routes injected via the "network", "aggregate-address" or "neighbor-default-originte" commands.

           

          Brian

           

          • 2. Re: show ip bgp "i" in AS path? but its eBGP...
            cadetalain

            Hi,

             

            If ther is no i just after the >  or * sign then this is not an iBGP learned route so it is a locally generated route in which case next-hop is 0.0.0.0 or an eBGP route.

            The last I as explained above is for the origin of the route that is how was he first put into the BGP table, it could be i or e or ? where e stands for egp which is predecessor to BGP and ? stands for unknown so was redistributed and i is via a network command or aggregate or the last one cited by Brian( I would have forgot this one).

             

            Regards.

             

            Alain.

            • 3. Re: show ip bgp "i" in AS path? but its eBGP...
              taz

              Hi. I'm stuggling with the difference too. I understand the 'i" at the end means its from "network" or "aggreagate" - i imagine for the AS whose number is to the left of it. This would be the origin in path selection ?? (weight/local pref/route originate/aspath/origin)

               

              So what is the "i" in the 3rd column meaning? Would that mean it originated on the router being looked at as opposed to another router? I think I need an example to clarify

              many thanks

              • 4. Re: show ip bgp "i" in AS path? but its eBGP...
                riedmueller

                Try this (stolen from a powerpoint)

                show ip bgp output.jpg

                • 5. Re: show ip bgp "i" in AS path? but its eBGP...
                  taz

                  THANK YOU!!!!!!!!

                   

                  That powerpoint slide is so sweet

                  • 6. Re: show ip bgp "i" in AS path? but its eBGP...
                    riedmueller

                    I agree. I wish I could remember where I found it so I could credit the author...