Hi Group, I have encountered this interesting problem on customer PBX. Didn't work on live system for a long time but I am pretty sure this shouldn't be a default behavior.
When external PSTN caller calls an unassigned number in the DID range, CUCM returns with error code 27 ( destination out of order). This causes the voice gateway to retry other dial-peers. There's 3 dial-peer which matches this e164 number. 1)Dial-peer 100 goes CUCM (longest match, most specific) 2)Dial-peer 200 goes CUCM (longest match, most specific) 3)Dial-peer 300 goes to PSTN (the destination-pattern is .T) When dial-peer 100 and 200 "fails", the voice gateway will dial-out to PSTN via dial-peer 300. Once again, PSTN route back to the customer VG. This causes a routing loop and it can fills up all the available E1 channels quickly. *Just wondering if anyone encounter the following issue and have a explanation to it? Just the engineering side of me want to get down to the root cause. * The CUCM have "stop routing on unallocated number" turns off (false). Just in case it matters. I tried to google around but can't seems to find any article that talks about 1) dial-peer behaviors (on voice gateway side) - on what error code will cisco voice gateway retry other dial-peers? 2) why CUCM returns error code 27? It's a managed service system so I'm unable to do a deep dive troubleshooting. The current workaround introduced is to create a dial-peer 250 with a higher preference that matches the DID range and block it. This means that incoming dialed number will match to 4 dial-peers (100, 200, 250 and 300) After failing on 100 and 200, the call gets block on dial-peer 250. -- Regards, Ki Wi
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