I have 2 vg in ccm, one (vg1) connect to Nortel pbx and the other (vg2) connect to PSTN. If Cisco IP phone activate CFwdALL to external via PSTN (vg2), someone call from Nortel phone via vg1 to IP phone, it can't forward to external and give busy tone. But, it works if other IP phone call to that IP phone. Is there any parameter setting in ccm to enable it?
CCM version: 4.1(3) sr3a