# GRE Tunnel keeps bouncing up and down



## TDT-TT (Apr 14, 2009)

I am having this issue and still have not find the solution or what cause the problem. The problem is the Spoke configured to have 3 tunnels to 3 different hubs using DMVPN technology and this has been working fine just over a year. Recently, I found out that there is a problem on Tunnel0 and Tunnel2. Ping is dropping on those tunnel and causing packet drop. GRE tunnel0 especially keeps bouncing up and down. Every time this happens EIGRP may flapping and I have to shut down Tunnel0 and Tunnel2 so all traffic to Tunnel1 and this has been working good so far. For example:
%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor (Tunnel2) is down: Peer goodbye received
%DUAL-5-NBRCHANGE: IP-EIGRP(0) 100: Neighbor (Tunnel2) is up: new adjacency
and this keep going on every few seconds for tunnel0 and tunnel2.
Does anyone have same problem and how to fix this?


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## dumb_guy (Jul 15, 2009)

Not sure if you ever got an answer... but I have seen this. 

Mostly on hight latency networks with bandwidth limitations. QoS policy has prioritized voice and video and left everything else best effort. 

The hello packets used to keep EIGRP neighbor states up are ICMP. During high traffic periods, these ICMP messages were getting dropped. In order to keep the tunnel states up, we had to extend the hold-down timers and hello-intervals. 

config# interface tunnel <tunnel#>
config-if# ip hello-interval eigrp <as#> 15
config-if# ip hold-time eigrp <as#> 45 

15 and 45 worked for us. Of course you can play with the time settings to meet your specifications.


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