There are 8 FXO interfaces on a router with 8 Trunk/PSTN links terminated on it. This FXO interfaces are grouped together with the trunk group command. so whenver the first line is busy automatically the next available link/line will be used.
I have observed that, if the link is removed from the first FXO port then the calls are dropped it does not go to the next available link/line in the trunk group. Then i have to manually shut the interface.
so is there an option available for the FXO interfaces that whenever the PSTN/Trunk link goes down it is detected and it starts using the next available lines in the group.
The way the line protocol status goes up and down with the serial or ethernet interfaces whenever the cable is removed.
From some of the documents i have come across that the FXO interfaces uses TIP and Ring mechanism. so basically it only detects the line going off-hook or on-hook. so does that means that it cannot detect the line protocol going down?
unfortunately FXO can't detect the line if it goes down. it only send and recive calls.
for your configuration, try to remove trunk config and use dialpeers with precedence. that means your config will become larger. for me I have alot of issuea with trunk especially when there is a line down. you can start with changing one dialpeer and test with removing one line to simulate the line down.
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Trunk-group can detect circuit failure and rehunt to next member. Configure a voice class causecode with "no circuit", and apply to the trunk group.
Please read this link to the command
dial-peer outbound status-check pots
no dial-peer outbound status-check pots
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The Following configuration detects the removal of the cable from the FXO interface:
After the cable removal, the operation state changes to "down" instead of "dorm" and the outgoing status changes to "off-hook".. This makes the port to be busy and thus the other available line in the trunk group is used for making calls.