Specific networks over Two DMVPN Tunnels/Links?

[graham.fleming]

I've got a primary DMVPN cloud that carries most VPN traffic between 5 sites. I've got a couple sites that have secondary links that I'd like to use to route only voice traffic over (unless of course there is a failure in which case either link will carry both). I'm wondering what's the best way of doing that.

Right now each DMVPN site advertises a series of /24 networks, one of those is the voice network.

I'm thinking initially to create a new DMVPN cloud, a new instance of EIGRP, and redistribute both EIGRP routes into each instance with some form of manipulation being done on the voice subnet's metrics so that it is preferred to run only on the secondary link. Does this sound like a sane starting point in my design?

Thanks!

[Rahul Kukreja]

In My opinion -

Not to use redistribution, as if it is not done properly - it may create loops.
Over the second tunnel - advertise only the voice subnets

2 options for the sites to send the voice traffic over second tunnel -

1. Use lower metric by playing with delay on second tunnel (if EIGRP AS is same for both tunnels)
2. If the metric is same and the same route is learned via 2 EIGRP AS, then EIGRP prefers lower AS and install that route in RIB. (if 2 EIGRP AS are used, then the lower EIGRP AS number should be used for advertising the voice subnets)

Regards,
Rahul

[graham.fleming]

Thanks for the suggestion. I was thinking I'd like to use both tunnels for all traffic in case there is a failure. This means if the second tunnel is only advertising the voice subnets then it can't back up the primary tunnel for data as well.

I've decided to just do it your way now as voice is definitely most important traffic and I'd worry about QoS if data traffic needs to go over the low-bandwidth voice feed.

How should I advertise only the voice subnets on that second tunnel? Since its the same EIGRP AS, do I need to use the summary address command on the tunnel interface?

Graham

[Rahul Kukreja]

Example -

On a Remote Site 2 LAN Segments :

Gi0/0.1 10.10.10.0/24 - data
Gi0/0.2 10.10.20.0/24 - voice

2 tunnels -

tunnel 1 - for both data and voice
tunnel 2 - dedicated only for voice

2 EIGRP AS -

AS 10 for both the traffic
AS 5 for only voice traffic (AS No. should be lower than 10)

Then for EIGRP config -

router eigrp 10
no auto
net 10.10.10.0 0.0.0.255
net 10.10.20.0 0.0.0.255
net tunnel 1

router eigrp 5
no auto
net tunnel 2
net 10.10.20.0 0.0.0.255

So on the EIGRP Neighbor, route for voice subnet 10.10.20.0/24 will be received via 2 neighbors with **equal metric**, and hence it will prefer the route learned over AS 5/tunnel 2 (lower AS)

This is just an example, the configuration may vary based on the exact phycical topology and how the LAN Segments are learned on Remote Site Router. You may ned to add few static routes / use redistribution int AS 5 if the voice subnet is not a directly connected one and consider the fact that routing should not go asymettric.

Regards,
Rahul