3.10.2.1. Requirements 
- The feature requires unrestricted Internet access with a static, public IP address for the OpenScape 4000 SoftGate server/service.
- An IP password must be assigned to the relevant phones in AMO SBCSU
- The phone in the remote office has to operate in secure mode, it has to be registered with TLS.
- The WAN interface of the OpenScape 4000 SoftGate requires a certificate. In case of SIP/UFIP the certificate is required for the Gateway to which SIP/UFIP subscribers are connected.
- The phone in the remote office has to use an NTP server (e.g. Internet Pool NTP) for time synchronization. The simplest way is to use an NTP server pool (e.g. 0.de.pool.ntp.org).
- For use of mobile HFA:
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To achieve a fully working mobile HFA scenario, the visit and home devices have to be configured on the same OpenScape 4000 SoftGate if the visit phone is the phone in the remote office.
- If an OpenScape Deployment Service (DLS) is used, both services, DCMP and DLS, have to be accessible via the public network. You will find additional information on the topic of "Configuring Home User Terminals for DLS/DCMP" in the Administrator Manual for the "OpenScape Deployment Service V8".
- For HFA SRS can be used across multiple vSTMI boards in a SoftGate. Hence the feature itself has no limit as to how many subscribers can be configured for SRS in the SoftGate.
- For SIP/UFIP phones however there is dedicated vSTMI board for SRS and its IP address must be known to the primary DMZ firewall and respective port forwarding rules for SIP signaling and media need to be configured. More vSTMI SIP cards (either on single SG or across multiple SoftGates) can be accessed only if there are created separate forwarding rules in the firewall distinguished by different ports, i.e. 5061, 5062, etc. (see Chapter 14, “Option 2: Scenario overview of DMZ with SoftGate DNAT option and multiple SoftGates”)