[c-nsp] MPLS VPN over mGRE

[John Neiberger]

The type of MPLS VPN over mGRE that we're using doesn't use a preconfigured
tunnel interface or NHRP. As I understand it, the peers share
tunnel-related information in vpnv4 updates using a SAFI of 64. This tells
the other peers that those prefixes are related to the mgre tunnel and that
signals the receiving router to set up an adjacency over the multipoint
tunnel, but I'm not quite sure how it does this. I don't understand what
element of the config tells the router to use SAFI 64 in the vpnv4 updates
instead of just treating them like regular L3VPN vpnv4 updates. It's kind
of confusing. There seems to be a lot of magic happening under the hood
here that I'm missing.

John


On Wed, Jan 30, 2013 at 1:15 AM, Adam Vitkovsky <adam.vitkovsky at swan.sk>wrote:

> Wow they really shrunk it down to three commands plus the route-map, now
> that's something.
>
> > or is there some other mechanism that triggers tunnel endpoint discovery?
> I believe since it's called mGRE it has to be NHRP taking care of
> everything
> in the background.
> Does the loopback IP has to be allocated from a common range that has to be
> shared among the PEs?
>
> I thought it's done via standard mGRE tunnels:
>
> interface Tunnel0
> ip address 192.168.1.1 255.255.255.0
> ip mtu 1440
> ip nhrp authentication cisco123
> ip nhrp map multicast dynamic
> ip nhrp network-id 1
> tunnel source FastEthernet0/0
> tunnel mode gre multipoint
> tunnel key 0
> ip router isis 1
>
> -maybe "mpls ip" cmd. wouldn't work with mGRE Tunnel Int.
>
>
> adam
>
>