Two OpenScape 4000 SoftGates are connected to one another (redundantly) in a pool. The "active" or "standby" function is defined by the configuration of the associated vHG3530 (HFA) / vHG 3500 (SIP) pairs. It is possible to configure both active gateways (AMO CGWB, SMODE=NORMAL) and standby gateways (AMO CGWB, SMODE=STBYRDY) within a OpenScape 4000 SoftGate. Two vHG3530 (HFA) / vHG 3500 (SIP) always form a pair. One gateway has to be configured in OpenScape 4000 SoftGate A in this case and the other in OpenScape 4000 SoftGate B.

Both IP addresses (primary gateway and secondary gateway) must be configured on the HFA/SIP phone. This can be administered on the terminal itself or via DLS.

Not all SIP phones support administration of two IP addresses ( primary and secondary server ). In this case DNSSRV must be used.