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This article describes the steps necessary to configure the SBC Edge (SBC) for SIP Trunking using Multiple IP Interface support .

Use Case Scenario

A typical use case scenario for the Multiple IP Interface support is: 

The SBC is connected to both a public network and a private (Enterprise) network, acting as a Session Border Controller (SBC) which effectively hides the topologies, IP addressing, signaling attributes and policies established between these two networks from each other. Calls from one network to the other are terminated on SBC (i.e. at the network border) and SBC establishes a different call on the other network, and enables end-to-end conversation.

In this example, the SIP trunking provider and the SBC are connected using the 10.51.100.X network. The enterprise has a IP range of 134.56.225.X. The SBC's main application bridge is configured to which is the default interface and has the default IP route pointing to it. The signaling and media packets for calls to and from OCS and LAN-1 endpoints will use as the IP address of SBC.

When calls are established over the SIP trunk, LAN-2 interface is used. In this case the SIP calls must use the interface IP of for the SIP messaging, SIP source IP address and RTP source IP address. This allows SBC to bridge the networks for calls and not simply route the IP packets.

The cleanest solution is to configure a single SIP Signaling Group for each network. The SIP SG pointing towards the ISP network should refer to LAN-2 interface. LAN-2 should be placed in ROUTED mode with an IP address in the range. The SIP SG pointing to the Enterprise network should use the Application-IP interface, which is the default.



SBC Configuration

This article assumes that a PSTN - SBC - OCS 2007 R2 configuration is already in place, therefore it is unnecessary to configure Media Profiles, Media List, SIP Profiles, SIP Server Tables, Tone Table, Telephony Mapping Table in this exercise.

From the SIP Trunking with Multiple IP configuration point of view, the following items must be configured in the SBC:

LAN Port 2/Ethernet 2 IP

    Configure the public IP address in the SBC. In the WebUI, access Tasks  and select Modify Ethernet IP Address.

    Note that LAN Port 1 is already configured on the node which you'd be using to URL into WebUI. Following screenshot depicts the verification of LAN 1 configuration:

    Configure the public IP address of in the SBC. In the WebUI, access Tasks  and select Modify Ethernet IP Address.

    Transformation Table

    Create four different transformation tables (for details, refer to Managing Transformation Tables):

    • Translation table for OCS (1xxx) extensions
    • Translation table for LAN-1 (2xxx) extensions
    • Translation table for LAN-2 (5xxx) extensions
    • Translation table for PSTN (3xxx) extensions

    Call Routing Tables

    Create three different Call Routing Table entries (for details, refer to Managing Call Routing Tables):

    • Routing Calls from OCS Endpoints
    • Routing Calls from Multiple IP Endpoints (LAN-1 and LAN-2 endpoints)
    • Routing Calls from PSTN Endpoints

    Signaling Groups

    Create four different Signaling Groups (for details, refer to Managing Signaling Groups):

    • Signaling Groups for OCS
    • Signaling Groups for LAN-1 endpoints
    • Signaling Groups for LAN-2 endpoints
    • Signaling Group for PSTN endpoints

    The LAN-2 Signaling Group refers to the IP subnet used between SBC and the SIP trunking provider. There are two subcases here.

    If there is a NAT device between SBC and the SIP-trunking peer, then NAT Traversal must be set to STATIC NAT and the public IP address of the NAT must be specified as the Application IP. In addition, the NAT device should be configured such that it translates between the private address of and the public address of

    If there is no NAT device between SBC and the SIP-trunking peer, then NAT Traversal must be set to NONE.

    Additional Configuration step for Ribbon SBC SWe Lite

    Adding Static IP Routes

    The previous steps complete the necessary configuration requirements for implementing the Multiple IP feature on the SBC 1000/2000. However, if deploying on the SBC SWe Lite, in addition to previous steps, add a Static IP Route to complete the Multiple IP feature support on the SBC SWe Lite. For details, refer to Managing Static IP Route Tables.

    All end-points located in a private or public network must be reachable through a next-hop gateway, as driven by the network environment.