I'm try to connect NORTEL CS1K Rls 4.5 ON SIP TRANKS (REDIRECT) TO LG IPECS. NEED HELP. WE HAVE PING BOTH SIDES. FROM NORTEL TO LG I GET ANSWER 501 ("SIP response 501") - 501 Not Implemented. FROM LG TO NORTEL THERE IS NOTHING ON THE SNIFER. WHAT TO DO?