In mVPN,what means " bgp peering address of PE " ?

In book "Definitive mpls network design" ,when refer to mVPN,which said:

3) If the olist contains a tunnel interface, the multicast packet is encapsulated using GRE.

The packet's source is set to the BGP peering address of the PE router.

The destination address is set to the MDT group address associated with the customer VPN.


what means  "the BGP peering address of the PE router" ?

Is that "peering address = neighbor xxx update-source ??"

If the PE router have mp-ibgp,mb-ebgp adjs, it will choose which peering address?

If we can manually chosen one as source address in mvpn GRE encapsulation ?


My regards!



  • It is IP address/interface you are using on the PE to establish iBGP session with other PE's (usually Loopback) for VPNv4 address family.

    GRE tunnel is built automatically, you are not configuring it. eBGP peering will take place only between ASes and mcast setup depends on Inter-AS option.



  • Thank seba for your help.

    But i dont understand a key point.

    For example :     PE1-------ASBR1------ASBR2

    here,pe1 and asbr1 belong to AS1,

    asbr2 belong to AS2.


    rotuer bgp 1

      nei pe1 remote 1

      nei pe1 update-source Lo0

      nei asbr2 remote 2

    add vpnv4 u

      nei pe1 activate

     nei asbr2 activate


    NOW: pe1 and asbr1 's vrf : mdt default

    asbr1 auto generate T0,and my question is, T0 will choose which ip address as T0 source address??

    Lo0 ??  or asbr1's direct link address ?? (which connect to asbr2,this address is bgp update-source for interAS mp-ebgp adjacency)

    If there is any method i can utilize to prefer one than another ?



  • What is the Inter-AS option in your setup? Remeber that for Inter-AS you will need some MSDP configuration, etc, but everything really depends on InterAS option.



  • Thank seba,i have understand !

    its depend on my interAS option!


    My earnest regards!

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