The following example creates a policy-based routing scheme in which:

The following figure illustrates the sample application described below.

This example includes a voice VLAN (6) and a data VLAN (5). The PMI is on VLAN 6. The Branch Gateway is managed by a remote Media Gateway Controller (MGC) with the IP address 149.49.43.210. The Branch Gateway also includes a local S8300 in LSP mode.

IP phones are located on the same subnet as the PMI. Therefore, there is no routing between the PMI and the IP phones.

In this example, the object of policy-based routing is to route all voice traffic over the E1/T1 line, which is more expensive but provides the superior QoS necessary for voice traffic. Remaining traffic is to be routed over the more inexpensive Internet connection.

It is assumed that the IP phones on VLAN 6 establish connections with other IP phones on the same subnet, sending signalling packets to the MGC, and bearer packets directly to other IP phones or to the Branch Gateway.

The policy-based routing configuring starts with PBR list 801. This list requires all voice packets addressed to the MGC (149.49.43.210) with DSCP values that indicate voice transmission (34, 41, 43, 44, and 46) to be routed according to next hop list 1. This list directs packets to the T1/E1 interface. If that interface is down, the packets are dropped.

In this example, it is important to include the destination IP address in each rule. This is because without the destination address, calls from IP phones on VLAN 6 to a Softphone on VLAN 5 will be routed by the PBR list to the E1/T1 line, rather than being sent directly to VLAN 5 via the Branch Gateway.