A C1117-4PM that is in ‘controller mode’ has been configured to use the VDSL for it’s primary internet connection to join overlay. VDSL interface negotiates and connects as expected and router is reachable/manageable on it’s public IP address without issue. The overlay connections to ALL other sites flap frequently, every 3-20 seconds. All other sites are on DIA or Ethernet handover. Have tried changing IP MTU on router and TCP MSS-Adjust to match or to cover overhead but no matter how low it is set the flapping continues. Have also tried changing interface circuit colour to be different/same as all other routers, no difference observed. Control connections to vManage/vBond/vSmart are solid throughout and do not see the same flapping. There are no ACLs configured that are different from other sites. ACLs removed did not improve connectivity any further.
