Hi Experts,
Kindly find attached the network topology in a jpg file. This is the network setup. I am not able to exchange the routes from DC1 to DC2 and vica versa. Both are in same AS. I am using ASR9001 IOS XR 5.3
There are 2 things that need to be catered here.
- When DC-GWs in DC1 send its routing information update over BGP to DC-GWs in DC2 via PEs, DC-GWs in DC2 checks the update and finds AS 65001 in the AS-PATH ; therefore due to BGP loop prevention mechanism DC-GWs in DC2 rejects the routes update from PEs because it finds its own AS in the update.
To overcome above problem I can use BGP AS Override functionality on PE routers. The AS Override command on PE will replace the DC-GWs AS number in DC1 with its own before it get advertised to DC-GWs in DC2 and vice versa.
This is to solve the problem of routes traversing between different Data Centers.
- When you apply above procedure, it will create an other issue which is routes from DC-GW2 in DC1 will also be advertised to DC-GW1 in DC1 (DC-GWs of the same Data Center) . To solve this , normally SOO (Site of Origin) attribute is used.
The configuration of SoO values for BGP neighbors is performed on a provider edge (PE) router as well, which is the VPN entry point. When SoO is enabled, the PE router forwards the prefixes to DC-GWs only when the SoO tag of the prefix does not match the SoO tag configured for the DC-GW.
You can set the SoO tag set as 65201:1 for Data Center 1 that includes routers in DC1 with an autonomous system number of 65201. When DC-GW1 sends prefixes to PE, PE tags the prefixes with 65201:1, which is the SoO tag for DC-GW1 and DC-GW2 in DC1.
Similarly for DC the SoO can be set to 65201:2.
Now please let me know if above thing is correct and if yes then the question is these are the ways to solve issues on PE side.
Is there a way that I can solve these issues on CEs without bothering the PE or they must be solved and resolved on PE ?
Any alternate solution that do not involve PE?
Thanks and Regards,
Ahmed
