Thanks Mark for the reply. Let me try to check what I understood is correct. Does the 'i' on the left (status code) only shows whether the prefix belongs to this AS?
What I want to figure out is if this two ASes (the owner of the router and and the first one on the AS-PATH) connect at the location of the router, or if packets need to stay for some hops in the local AS. On Wed, Mar 11, 2015, 2:51 PM Mark Tinka <mark.ti...@seacom.mu> wrote: > > > On 11/Mar/15 20:32, Reza Motamedi wrote: > > Hi Nanog, > > > > For a research I want to distinguish the external AS peering from "show > ip > > BGP". In other words I want to see which entry show a path that > immediately > > sends packets to another AS. My understanding is that *status code* shows > > if the route is internal, right? Does this mean if the *'i' *is not > > present, the route is goes out of the AS in the next hop. On the same > note, > > can I use "Next Hop" to identify such entries? > > > > I just included a sample report from a public looking glass in XO. > > > > > > show ip bgp 207.108.0.0/15 longer-prefixes > > BGP table version is 529230540, local router ID is 65.106.7.145 > > * * *Status codes: s suppressed, d damped, h history, * valid, > best, > i - > > internal, > > r RIB-failure, S Stale, m multipath, b backup-path, x > > best-external, f RT-Filter, a additional-path > > Origin codes: i - IGP, e - EGP, ? - incomplete > > > > Network Next Hop Metric LocPrf Weight Path > > * 207.108.0.0/15 216.156.2.164 3 0 2828 209 > i > > * 65.106.7.101 2 0 2828 209 i > > * 65.106.7.246 3 0 2828 209 i > > * 65.106.7.55 3 0 2828 209 i > > *> 216.156.2.162 2 0 2828 209 i > > * 65.106.7.54 3 0 2828 209 i > > * 65.106.7.252 2 0 2828 209 i > > * 216.156.2.160 2 0 2828 209 i > > * 65.106.7.56 3 0 2828 209 i > > * 216.156.2.165 2 0 2828 209 i > > * 65.106.7.144 2 0 2828 209 i > > There are two uses of the "i" code in IOS: > > 1. "i" for Status codes refers to the route being learned via iBGP. > 2. "i" for Origin codes refers to the route being learned via a > locally-generated route at the origin (or more historically, the IGP). > > In IOS "show ip bgp" output, the "i" for Status code (iBGP) is to the > left of the prefix. On the other hand, the "i" for Origin code > (IGP-originated route) is to the right of the originating AS in the > AS_PATH. > > So you need to be more interested in the "i" to the left of the prefix. > In your output above, no such "i" exists; ergo, these are eBGP-learned > routes from this router's point of view. > > Use of the NEXT_HOP attribute to identify whether a route is > eBGP-learned is not reliable, especially if you do not own the network > you're getting your data from. > > Mark. > >