Hello all I setup the Asterisk without Line Card. But UA could not speak each other. Error log was as follow Asterisk Ready. WARNING[5126]: File chan_sip.c, Line 444 (retrans_pkt): Maximum retries exceeded on call 5b5b1f1a2d21623450ba083b22d62612@192.168.0.100 for seqno 102 (Request) Please give us suggestion to communicate each UA. config as follow Asterisk IP address:192.168.0.100 extensions.conf [sip] exten => 1001,1,Dial(SIP/1001,5) exten => 1001,2.Voicemail(u1001) exten => 1001,102.Voicemail(b1001) exten => 1001,103,Hangup exten => 1002,1,Dial(SIP/1002,6) exten => 1002,2.Voicemail(u1002) exten => 1002,102.Voicemail(b1002) exten => 1002,103,Hangup sip.conf ; [general] port = 5060 bindaddr = 0.0.0.0 context = sip ;srvlookup = yes ;pedantic = yes Pingtel ;tos=lowdelay ;tos=184 ;maxexpirey=3600 ;defaultexpirey=120 [1001] type=friend username=1001 secret=secret host=dynamic mailbox=1001 context=sip [1002] type=friend username=1002 secret=secret host=dynamic mailbox=1002 context=sip