BGP Routes Advertised Twice

[sabina-anja]

So, the general idea of the config is as it follows - the peering for this setup is done from one AS to two other ASes (that are also connected via another provider, so the two other ASes belong to the same entity, while they connect to my AS). The trouble is, every time I do a sh ip bgp vpnv4 for that particular VRF I can see the routes advertised twice.

The 10.250.250.127 is the other peer for the current router and it travels a number of other devices (it's a U-shaped deployment, in which the node listed below is one end and the 127 is the other end). At the bottom there are two route reflectors which might responsible for this.

The 10.64.66.9 is the directly connected peer from one of the ASes.

The question is, is this kind of advertisement normal? I know that only one path is chosen as valid and best, while the other one is just a valid route, but then again, should it look like this?

#sh ip bgp vpnv4 vrf <vrf name>

 *>i 10.64.66.16/30   10.250.250.127           0    100      0 65128 ?
 * i                  10.250.250.127           0    100      0 65128 ?
 *>i 10.64.66.20/30   10.250.250.127           0    100      0 ?
 * i                  10.250.250.127           0    100      0 ?
 * i 10.64.68.248/29  10.250.250.127           0    100      0 65128 65222 6830 6830 ?
 *>                   10.64.66.9                             0 65110 65222 6830 6830 ?
 * i 10.64.71.0/25    10.250.250.127           0    100      0 65128 65222 6830 6830 ?
 *>                   10.64.66.9                             0 65110 65222 6830 6830 ?
 * i 10.64.71.128/25  10.250.250.127           0    100      0 65128 65222 6830 6830 ?
 *>                   10.64.66.9                             0 65110 65222 6830 6830 ?
 * i 10.64.72.0/25    10.250.250.127           0    100      0 65128 65222 6830 6830 ?
 *>                   10.64.66.9                             0 65110 65222 6830 6830 ?
 * i 10.64.72.128/25  10.250.250.127           0    100      0 65128 65222 6830 6830 ?
 *>                   10.64.66.9                             0 65110 65222 6830 6830 ?
 * i 10.64.73.0/25    10.250.250.127           0    100      0 65128 65222 6830 6830 ?
 *>                   10.64.66.9                             0 65110 65222 6830 6830 ?

Thanks!

[Nagendra Kumar Nainar]

Hi Sabina,

Not sure, I understood your query. Do you mean routerX from where you took this bgp output have 10.64.66.9 as eBGP and 10.250.250.127 as iBGP?.

If so, and if there is no RR in between and if both are choosing eBGP advertised as best path, it is normal to see the iBGP received prefix in table.

If your query is different, please clarify and a simple topology will be helpful for better clarity.

-Nagendra