Multi-homed Server Configurations Overview

4-12 Oracle WebLogic Communications Server Administration Guide Figure 4–3 Multi-homed Configuration for Proxying between Subnets To configure the Oracle WebLogic Communication Services instance in Figure 4–3 you must define a separate network channel for each NIC used on the server machine. Example 4–3 shows the config.xml entries that define channels for the sample configuration. Example 4–3 Sample Network Channel Configuration for NICs on Multiple Subnets NetworkAccessPoint ListenAddress=10.1.1.10 ListenPort=5060 Name=sipchannelA Protocol=sip NetworkAccessPoint ListenAddress=10.2.1.10 ListenPort=5060 Name=sipchannelB Protocol=sip

4.8.4.1 Understanding the Route Resolver

When Oracle WebLogic Communication Services is configured to listen on multiple subsets, a feature called the route resolver is responsible for the following activities: ■ Populating OSI Layer 7 information SIP system headers such as Via, Contact, and so forth with the correct address. ■ Populating OSI Layer 3 information with the correct source IP address. For example, in the configuration shown in Figure 4–3 , Oracle WebLogic Communication Services must add the correct subnet address to SIP system headers and transport datagrams in order for each UA to continue processing SIP transactions. If the wrong subnet is used, replies cannot be delivered because neither UA can directly access the other UAs subnet. The route resolver works by determining which NIC the operating system will use to send a datagram to a given destination, and then examining the network channel that is associated with that NIC. It then uses the address configured in the selected network channel to populate SIP headers and Layer 3 address information. For example, in the configuration shown in Figure 4–3 , an INVITE message sent from Oracle WebLogic Communication Services to UAC B would have a destination address of 10.2.1.16. The operating system would transmit this message using NIC B, which is configured for the corresponding subnet. The route resolver associates NIC B with the configured sipchannelB and embeds the channels IP address 10.2.1.10 in the VIA header of the SIP message. UAC B then uses the VIA header to direct