[Serusers] Bug or feature?

Folks, This question isn't directly related to a SER, but does anybody know why Cisco IOS inserts several identical `c=<IP>' lines in SDP which it generates? No other UA I know about does that. I wonder because it creates a problems with SDP rewriting in nathelper module and I need to decide whether I have to modify nathelper to cope with that or open a Cisco TAC case instead. Any comments are appreciated! -Maxim SIP/2.0 200 OK Via: SIP/2.0/UDP 67.104.130.102:5061 From: <sip:0118000@67.104.130.102:5061;user=phone>;tag=bb4b39670c51e5c737c5de99b5450cc5 To: <sip:61412722777@64.180.102.72;user=phone>;tag=357A3908-2F6 Date: Tue, 17 Jun 2003 07:35:12 GMT Call-ID: 2920698556(a)192.168.1.100 Server: Cisco-SIPGateway/IOS-12.x CSeq: 2 INVITE Allow: INVITE, OPTIONS, BYE, CANCEL, ACK, PRACK, COMET, REFER, SUBSCRIBE, NOTIFY, INFO Allow-Events: telephone-event Contact: <sip:61412722777@67.104.130.107:5060> Content-Type: application/sdp Content-Length: 285 v=0 o=CiscoSystemsSIP-GW-UserAgent 7069 1539 IN IP4 67.104.130.107 s=SIP Call c=IN IP4 67.104.130.107 ^^^^^^^^^^^^^^^^^^^^^^^ t=0 0 m=audio 19044 RTP/AVP 4 19 101 c=IN IP4 67.104.130.107 ^^^^^^^^^^^^^^^^^^^^^^^ a=rtpmap:4 G723/8000 a=rtpmap:19 CN/8000 a=fmtp:4 annexa=no a=rtpmap:101 telephone-event/8000 a=fmtp:101 0-15