WAN Interface in VLAN COnfiguration

[abc1235]

Hallo,

I have an ISR 1100 Router connected to two C9200 switches. However, I have observed that all three devices are flapping a lot. On checking further, one of the C9200 ports connected to the ISR router's WAN port (Gi0/0/0) is in VLAN800 but Gi0/0/0 is not in any VLAN. I am not sure if this is good practice or whether it can work but can the WAN port be configured to be in VLAN800?

Thanks for the help.

[abc1235]

Hallo @Richard Burts, 

We found out that the DSL router was not registering the MAC address of the ISR router resulting in the tunnels flapping. Everything is now working perfectly fine. Thanks for your engagement.

[Richard Burts]

Thanks for the update and for sharing the explanation of the problem. Sounds like good troubleshooting to find this. So a well deserved +5.