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I'm trying to establish connectivity between Hub and Spoke locations of same enterprise with same AS using BGP. Within DC (hub) iBGP and OSPF is used and eBGP is established between Spokes and MPLS Routers and Hub and MPLS routers.

Want that HUB and Spoke to communicate with each other without changing the MPLS and HUB redundancy. But the problem is HUB and Spoke are not able to communicate because they have same ASN. How can I deal with this ?

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  • It's not clear what you're asking. Do you want 5.5.5.5 to learn the prefix 6.6.6.6? Your design would be much simpler if you removed the cross links from the HUB to the MPLS network. DC-1 should connect to AS100 only and DC-2 should connect to AS 200 only. – Ron Trunk May 23 at 14:01
  • a. Want connectivity between Spokes (BR-1,Br-2) to access 192.168.1.0 network on R11 – danish May 23 at 14:07
  • b. DC-1,DC-2 are deliberately connected with multiple links to establish redundancy – danish May 23 at 14:08
  • Br1 can't learn br2's routes because they're in the same AS. You can make each site their own AS. – Ron Trunk May 23 at 14:23
  • Correct but Hub and spoke belong to same organization and have same AS – danish May 23 at 14:45
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Now Routes learned by AS100/200 Routers from HUB and Spoke are not advertise to each other. How can I deal with this?

One method is to build a GRE tunnel between:

  • BR-1 and DC-1
  • BR-2 and DC-2

Ensure you run a single IGP in AS1 (including the tunneled interfaces). Now fire up iBGP between your disparate AS1 sites (note I'm assuming you know how to fully mesh an iBGP topology).

Preferrably you should use routers which process GRE tunneled packets in hardware (as opposed to the IOS software path).

Note... the best way to solve this problem is to get some private lines between the two AS1 instances... that way you don't need GRE or to run iBGP through AS100 and AS200.

  • In that case, MPLS routers needs to have static route to hub and spoke. Also can I ensure redundancy of MPLS and HUB routers using this ? – danish May 23 at 15:25
  • The MPLS routers already have the routes for your AS1 external interfaces in their IGP / routing tables because your external interfaces are connected to them. To the question of redundancy, yes this response above is both router and link redundant. – Mike Pennington May 23 at 15:27
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Another option is to use private AS numbers for each location. In this way, the MPLS networks become the hub. You will have to decide if changing the AS numbers is more complicated than building and addressing GRE tunnels.

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