I just had an issue where the the phone on the first extension showed a "Layer 1 Link Error" which caused us to not be able to establish a line out, it would say "BUSY - All lines are busy". We could still ring internal extensions.

I could ping the SIP trunk server from my PC OK.

After I rebooted the router and the SV9100 switch, all was fine.

I'm just wondering if anyone has experienced this or knows what could have caused it?

Thanks

Here in the US layer 1 indicates a carrier issue.