Cisco Support Community
Community Member

ISDN Call from PSTN return to PSTN !!!

Hi, in configuration below I have problem because when CallManager ( is unreachable or the specyfic called number (DN) 3001.... is unconfigured on the CallManager the call go back to PSTN and the circle occures as long as the free B-channles ale available. This is confusing. How to block and terminate the call that came from PSTN not to go back to PSTN. Is something like "NULL" dial-peer which terminate configured calls and sends back disconnect code like "unassigned number or something like this".

dial-peer voice 100 pots

destination-pattern .T


port 1/0/0

forward-digits all


dial-peer voice 1 voip

destination-pattern 3001[123456]..

voice-class codec 1

session target ipv4:

no vad


Any suggestions



Re: ISDN Call from PSTN return to PSTN !!!

Change the destination pattern on the POST dial peer to be something more specfic than just .T - when the call fails on the VOIP dial peer, the router decides the .T is a close enough match so the call gets hairpinned back out. Best thing is configure the CM to leave the leading access code (eg , 0 or 9) on the called number and make the outgoing POTS dial peer use this as the destination pattern.

Community Member

Re: ISDN Call from PSTN return to PSTN !!!

you can make a translation pattern in callmanager that would match number

3001[1-6]xx translate this number to a unused extension number say 1234 or what ever fits your dial plan. then create a cti route point or a dummy phone. give it extension 1234 set all the forwards to forward to you voice mail. then create a new voice mail box 1234 set it to not take a message just play a greatting and hang up. then record a creating that say you have reached a number that is not in service or what ever you want to say.

hope this helps


CreatePlease to create content