Voice over IP (VoIP) SIP Telephony119information is available for NAT on an incoming RTP connection.To avoid thisproblem, the IP address of a workstation computer or telephone visible on theInternet is determined using a STUN server (STUN: Simple Traversal of UDP overNAT). You can ask your SIP provider for the STUN server.’s IP address and portnumber If you don’t need a STUN server, leave the SIP Provider field empty.■ For direct SIP telephony using OpenCom 510, only SIP IDs consisting ofnumbers for identifying subscribers registered with the SIP provider specifiedcan be addressed■ For each SIP account you can create just one bundle. You can specify thisbundle in routes as a connection option. You can use a network provider ruleto specify the routing of numbers within a specific range to use SIP telephonyas a preference (see also PBX Networking, under Configuration starting onpage 154).You can configure SIP connections in the Configurator on the pagesPBX Configuration: SIP trunks: accounts and PBX Configuration: SIP trunks:provider. Enter the technical attributes of a specific SIP provider, such as the IPaddresses for the registrar and the STUN server under Provider. Under Accountsenter the information for an existing SIP account, such as the user name, password,assigned call number and the maximum number of simultaneous calls possible.10.4.2 Internal SIP subscribersThe OpenCom 510 becomes available as the SIP server for internal SIP subscribertelephony switching services. SIP telephones connected via LAN or SIP pro-grammes installed on workstation computers can thus establish connections to allother devices or trunks connected to the OpenCom 510. For operation as a SIPserver a MG+ETH1-1 is required.licence assignmentThe number of possible SIP subscribers is determined by the number of licencespurchased. In order to provide you with the greatest possible flexibility regardingusage of available licences, licence assignment is dynamic via the “Floatinglicence”. Using a user/code word combination (“SIP log on”) you can have severalSIP subscribers under the same call number. Only every new SIP log-on occupies anew licence. The technical log-on process of a SIP subscriber with a valid username and correct code word is always successful. Only when a connection isestablished is there an attempt made to occupy a licence under the SIP log-on. If
