DMVPN and HSRP

Unanswered Question
Oct 11th, 2008

Can someone point me to a doc on how to configure DMVPN on a couple of routers with HSRP configured. Do I use the VIP address when I'm configuring the spoke tunnel interface?

I have this problem too.
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Nagendra Kumar ... Sat, 10/11/2008 - 21:27

Hi Rockburn,

Normally HSRP relates with LAN interface and DMVPN with WAN interface.

While configuring DMVPN, you need to create a tunnel interface with tunnel source as some address which can be reached from the other sites (loopback in most of the case). So I feel HSRP Virtual IP address may not have a role in DMVPN deployment.

Regards,

Nagendra

Brent Rockburn Sat, 10/11/2008 - 22:22

Yes but you can have two routers with gig interfaces facing the WAN and have VPN tunnels terminating there. So it must be possible to have some sort of dual hub configuration. I'm just wondering if GRE DM tunnels are different. I can't find a lot of info on it.

Giuseppe Larosa Sat, 10/11/2008 - 22:56

Hello Brent,

if the two routers are spokes you can think to configure both to take part in DMVPN: they will advertise the same internal IP subnets:

if using iBGP one will be preferred if using an IGP both will be installed in the routing tables of other devices.

If the two routers are hub you can think of providing all the NHRP mapping info to reach each other inside mGRE tunnel configuration.

I had tried in some tests to use a loopback as tunnel source but it wasn't possible to use it: the tunnel source has to be the exit interface towards the WAN cloud.

From the other thread on DMVPN

on hub 1:

int tu0

ip nhrp map 10.100.106.4 172.24.2.4

ip nhrp map multicast 172.24.2.5

you need to link together the NHRP info on both hubs

Hope to help

Giuseppe

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