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In a typical network layout (see below), an SBC 1000 has both a public interface connected to the internet, and a private interface connected to the corporate network. A user's home network is also attached to the network with a NAT router and a SIP phone behind it. In this example, SIP requests arrive at the SBC from the Home SIP Phone wih the SIP Phone's private IP address (i.e., 192.168.10.2). With Inbound NAT Traversal enabled, the SBC 1000 can detect the public IP address (i.e. 134.56.216.210). Once this detection is made, all communication to this endpoint is sent to the public IP, rather than the private IP from the Home SIP Phone.

Configure an SBC Edge in a NAT Traversal Environment

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1. In the left navigation pane, go to SIP > NAT Qualified Prefix Tables.
   
   

2. Click the Create NAT Qualified Prefix Table Entry ( ) icon at the top of the SIP NAT Qualified Prefix Tables page.
   
   
3. In the Description field, enter a description for the table (i.e., Default Private Prefixes).
   
   
4. Click OK. The table is created.
   
   
5. From the left navigation pane, click on the table just created.
   
   
6. Click the Create NAT Qualified Prefix Table Entry ( ) icon at the top of the table.
   
   
7. Configure the options. For field definitions, see Creating and Modifying a NAT Qualified Prefix Table.
   
   

8. Click Apply.

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   Caption 0 Figure 1 Create NAT Qualified Prefix Table Image Modified

Step 2: Associate NAT Qualified Prefix Table to Signaling Group

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1. Select the signaling group in which the NAT Qualified Prefix will be associated.
   
   

2. Access the Inbound NAT Traversal options.

   Info
   Do not confuse the Inbound NAT Traversal fields with the Outbound NAT Traversal fields in the SIP IP Details section. The Outbound NAT Traversal fields are used when the SBC is on the private side of a NAT device.

3. From the Detection drop down list, select Enable.
   
   

4. From the Qualified Prefixes Table drop down list, select the applicable table you created in Step 1. When examining SIP packets, this table determines which Subnets should be treated as being behind a NAT device.
   
   

5. Configure optional fields (i.e, Secure Media Latching, Secure Media Netmask and Registrar Max. TTL Enabled). For field definitions, see Creating and Modifying SIP Signaling Groups.

6. Click Apply.

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   Caption 0 Figure 1 Associate NAT Qualified Prefix Table to Signaling Group Image Modified

Guidelines/Recommendations for using NAT Traversal

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