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BGP Routing in DMVPN Networks

Once you decide to use BGP as the routing protocol in your DMVPN network, you face a few more design choices:

  • Should you use IBGP or EBGP?
  • Should you use a unique AS number for every DMVPN site, or the same AS number on all spoke sites?

The BGP Routing in DMVPN Access Networks ExpertExpress case study describes these dilemmas in more details; if you face a similar problem and would like me to review your design, get in touch.

4 comments:

  1. Hello, Ivan.

    Do you have any estimations regarding the number of BGP peers (spokes) per Hub?

    Some years ago our company designed DMVPN with BGP, but Cisco experts put a veto, because of number of peers we were expecting.
    We had to go into production with EIGRP that time.

    Thanks.
    Replies
    1. Cisco Live presentations claim BGP scales way better than EIGRP. Look at https://www.ciscolive365.com/connect/sessionDetail.ww?SESSION_ID=7929
  2. Is the use of BGP (whether iBGP or eBGP) over DMVPN still feasible when you peer with your provider using BGP for WAN routing?

    It lends itself easily to address families/VRFs but the only way I could control my own AS numbers was with the replace-as function which feels dirty.
    Replies
    1. If you use BGP for Internet access or MPLS/VPN then you hopefully have different AS number on each site, so it's easy to reuse them for DMVPN (where it's best to use EBGP anyway).

      You might need a transport VRF though.
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