Dual DMVPN Tunnel with 4G failover

[Gordon Blakey]

I am currently working on a solution for multiple sites that will have a Cradlepoint 4G modem as a failover in case their primary connection(Typically a DSL connection) goes down.

We use a DMVPN hub to spoke connection to each location using either a 1811 or 891 router at the spoke end and I currently have the failover working via EEM script. The only issue is that the failover is taking on average about 2 minutes to rebuild the tunnel connections back to the head end router. I would like to hear your suggestions on getting this failover to switch over more quickly. Keep in mind that each spoke router has a connection to two different DMVPN routers.

I apologize ahead of time as I did not build this network initially and I am simply in charge of getting this failover to work properly. I will do my best to answer your questions.

Enclosed is part of the configuration from the spoke router with some information removed for security reasons. I am including the tunnel configuration as well as the EEM script.

Thanks ahead of time for taking a look.

[paul driver]

Hello

Eigrp wont declare the adjacency dead until the hold time has expired, so decreasing this with the hello interval can make eigrp converge quicker.

Changing the Hello/Hold interval is a interface specific command and it results in the neighboring peer receiving the values

example:
int tun xx
ip hello-interval eigrp xx 5
ip hold-time eigrp xx 15

Hold time = 3x hello interval

Can you post: the following to check the advertised eigrp intervals your spokes are receiving, I think it should a 5/15 respectively on a tunnel interface?

sh ip eigrp neigbours

res

Paul

[Gordon Blakey]

I tried applying the Hello/Hold commands but it doesn't appear to be working.

Here are the results from sho ip eigrp neighbors:

EIGRP-IPv4 Neighbors for AS(29)
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   192.168.29.3            Tu0               13 03:48:19  613  3678  0  24370633
EIGRP-IPv4 Neighbors for AS(52)
H   Address                 Interface       Hold Uptime   SRTT   RTO  Q  Seq
                                            (sec)         (ms)       Cnt Num
0   10.75.52.3              Tu52              10 03:47:46  811  4866  0  29567417
EIGRP-IPv4 Neighbors for AS(54)

[paul driver]

hello

I am thinking this could be a SIA issue - (stuck in active), Which means eigrp is possibly querying its feesable successor ( backup router) for a different path to a lost network and its not receiving a responce within the default SIA time  ( 180 seconds)

Can you post the following when the primary links fails and also any historical logging you may have?
 

sh ip eigrp topology
sh ip eigrp topology active
sh ip protocols | in Active

res

Paul

[Hitesh Vinzoda]

Have you thought of using ip sla on the route and use floating static route for underlay routing protocol instead of relying on eem.

Hth

Hitesh

[Gordon Blakey]

Could you provide me of an example of how that would work with my configuration?

[kpyz00001]

Hi Gordon.

I need a little help from you on the DMVPN with 4G backup or failover.

The last time I worked on this technology was year 2009. I am looking forward to getting engaged more frequently from now on. Reading your request to the community shows you;ve been on this tech for a while. I will need some literature that deals with the technology in-terms of setup, config and management.

Please I need your assistance.

Thanks