Today I found a very strange problem on a fresh Asterisk 220.127.116.11 install. The customer wants to use SIP Softphones, so I tested out Zoiper and Draytek Softphone on the server. Everything worked, except for Blind Call Transfer. When I want to do a Blind Call Transfer, I get the following output on the CLI (same on both softphones):
Call from 201 to 220 (softphone), then I want to blind transfer the active call from 220 to 201: == Using SIP RTP CoS mark 5 -- Executing [220@iternal_calls:1] Dial("SIP/201-00000078", "SIP/220,20,tT") in new stack == Using SIP RTP CoS mark 5 -- Called 220 -- SIP/220-00000079 is ringing -- SIP/220-00000079 answered SIP/201-00000078 -- Started music on hold, class 'default', on SIP/201-00000078 -- Stopped music on hold on SIP/201-00000078 == Spawn extension (internal_calls, 202, 1) exited non-zero on 'SIP/201-00000078'
The problem is that the ext. 201 doesn’t get any SIP packets at all. When I want to do a Blind Call Transfer on a softphone, both legs of the call are dropped. If I want to do a Blind Call Transfer on an ordinary SIP Phone, there is no problem at all.
I really do not see what can be wrong in the configuration, my extensions.conf entrys for the extensions are simply:
exten => 201,1,Dial(SIP/201,20,tT) exten => 202,1,Dial(SIP/202,20,tT) exten => 220,1,Dial(SIP/220,20,tT)
It’s the same thing if I use t or tT as Dial application arguments.
The funny thing is, that when I tried the same thing with the same softphone on my Asterisk server that is running 18.104.22.168, Blind Call Transfer works without any problems on the Softphone.
Has something strange happened in the latest versions of Asterisk. I found a similar problem here, but there is no solution (using call parking or Blind Call Transfer via # transfer is not a solution in my book):
If someone needs it, I also have a SIP trace of the call. SIP packages are as follows:
- ext 220 sends SIP REFER to Asterisk
- Asterisk responds with 202 Accepted
- Asterisk drops both calls
I really hope there is a config issue here because I would hate to downgrade the server …