Polycom RMX 1500 Administrator's Manual page 1070

Appendix H-Setting the RMX for Integration Into Microsoft Environment
H-84
The Default IP Service - Networking IP dialog box opens.
4
Make sure the IP Network Type is set to H.323 & SIP even though SIP
will be the only call setup used with Office Communications Server
2007.
5
Make sure that the correct parameters are defined for the Signaling
Host IP Address, Media Card 1 IP Address, Media Card 2 IP Address
(RMX 2000/4000 if necessary), Media Card 3 IP Address (RMX 4000 if
necessary), Media Card 4 IP Address (RMX 4000 if necessary) and
Subnet Mask.
Make sure that the IP address of the RMX Signaling Host is the same one
defined as a trusted host in Office Communications Server 2007/Lync Server
2010.