2

Topology of the network: enter image description here

R1 and R2 are iBGP 
R3 and R4 are iBGP

R1 - R3 eBGP
R2 - R4 eBGP

I want R1 to direct the traffic for R2 to go through R3, R4 then to R2 and then back the same way in reverse.

I have tried manipulating LOCAL_PREFERENCE on R3/R4 but when I check the ip bgp there is still only one route to R2.

All routers are next-hop-self to their iBGP neighbor.

Output config show ip bgp 10.2.0.0

Output for R1 is Local 2.2.2.2 from 2.2.2.2 Origin IGP, localpref 100, valid, internal, best

Output on R3 with the inclusion of locpref is: 4.4.4.4 from 4.4.4.4 Origin IGP, localpref 200, valid, internal, best

4

By default R1 will drop the route to R2 received form R3 because the AS path contains R1's AS. On cisco you can use allowas-in to stop this default behaviour though I've never done this myself and I guess you could get yourself in a right pickle if you were to implement it wrong.

  • using allowas-in opens up the potential for alternate routes, thank you – Daniel Nov 10 '16 at 21:08

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