--- span_1 = DAHDI/g11 1,1,dial(${span_1}/${EXTEN:0}) --- The configuration was rsync'd from a working pair of asterisk servers in another office. The only difference was the version 1.4.22 for the original servers that were operating as expected, 1.4.24 and 1.4.24.1 for the new servers. Included in both working and non working servers is the following configuration: /etc/asterisk/chan_dahdi.conf --- #include /etc/asterisk/dahdi-channels.conf --- /etc/asterisk/dahdi-channels.conf --- ; Span 1: TE2/0/1 "T2XXP (PCI) Card 0 Span 1" (MASTER) B8ZS/ESF ClockSource group=0,11 context=DID_span_1 switchtype = national signalling = pri_cpe channel => 1-23 context = default group = 63 --- /etc/asterisk/users.conf (asterisk 1.4.22 w/ SVN-branch-2.0-r4657 GUI) --- [span_1] group = 1 hasexten = no switchtype = national signalling = pri_cpe trunkname = Span 1 trunkstyle = digital ; GUI metadata hassip = no hasiax = no context = DID_span_1 zapchan = 1-23 --- /etc/asterisk/users.conf (asterisk 1.4.24[0-1] w/ SVN-branch-2.0-r4661 GUI) --- group = 1 hasexten = no switchtype = national signalling = pri_cpe trunkname = Span 1 trunkstyle = digital ; GUI metadata hassip = no hasiax = no context = DID_span_1 zapchan = 1-23 dahdichan = 1-23 --- The dial command above did not work on the second group of servers. Instead I had to change the group to 1 thus: