Peplink fails to talk to the router

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Situation: The client use Peplink to connect ICN and Comcast router. The Comcast is default router. The Comcast service is down and comes back. However the Peplink doesn't switch back to default Comcast router.

Troubleshooting: Even the Comcast router comes back, but can't ping the router from the Internet. that means the Comcast still has return issue. After the second rebooting Comcast router, we can ping the router and Peplink switch back to the Comcast.