We are using EIGRP to propagate routes thru VTI with IPSEC from our HQ to our branches, using 3 provider. On one of the link, the EIGRP is often down and comes up right away ( flapping ? ) thus making our link unstable and slow. we are using a same configuration for each provider/link. is the issue come from the provider or our configuration ? should we change our EIGRP hello/holdtime from the default to 60/180 ? ( our link is 256 ) , or is there any particular thing we could do to assess this problem further ?
You do not tell us how many remote sites you have. But if you have multiple sites using Virtual Tunnel Interface with EIGRP and only one of them is having problems then it is not so likely that it is a problem in your configuration. Have you verified that the site with the problem is running the same version of code as the other sites? Have you verified that the site with the problem is really configured the same as the other sites? Perhaps using show interface to comare interfaces on a site that works ok with the site that has problems might show some issue. Or perhaps you can do some testing to check connectivity to the site that is experiencing the problem. One simple approach would be to use ping to and from the site with the problem. If you have the ability to send a slow ping that would be good. If it were me I would probably set up a ping that sent a packet every 10 seconds (no need to send lots of ping packets very quickly which impacts link utilization, what you want is to find whether over a period of time there are significant packet loss).