Administration of the Avaya G350 Media Gateway - Avaya Support

Configuring policy-based routingPolicy-based routing only operates on routed packets. Packets traveling within the same subnetare not routed, and are therefore not affected by policy-based routing.The Loopback interface is a logical interface which handles traffic that is sent to and from theG350 itself. This includes ping packets to or from the G350, as well as telnet, FTP, DHCP Relay,TFTP, HTTP, NTP, SNMP, H.248, and other types of traffic. The Loopback interface is also usedfor traffic to and from analog and DCP phones connected to the device via IP phone entities.The Loopback interface is always up. You should attach a PBR list to the Loopback interface ifyou want to route specific packets generated by the G350 to a specific next-hop.Unlike the case with other interfaces, PBR lists on the Loopback interface are applied topackets when they leave the G350, rather than when they enter.Certain types of packets are not considered router packets (on the Loopback interface only),and are therefore not affected by policy-based routing. These include RIP, OSPF, VRRP, GRE,and keepalive packets. On the other hand, packets using SNMP, Telnet, Bootp, ICMP, FTP,SCP, TFTP, HTTP, NTP, and H.248 protocols are considered routed packets, and are thereforeaffected by policy-based routing on the Loopback interface.ApplicationsThe most common application for policy-based routing is to provide for separate routing of voiceand data traffic. It can also be used as a means to provide backup routes for defined traffictypes.Separate routing of voice and data trafficAlthough there are many possible applications for policy-based routing, the most commonapplication is to create separate routing for voice and data traffic.For example, the application shown in Figure 24: Policy-based routing — Voice/Data DivisionBy DSCP on page 275 uses the DSCP field to identify VoIP control packets (DSCP=34, 41),VoIP Bearer RESV packets (DSCP = 43, 44), and VoIP Bearer packets (DSCP = 46).Policy-based routing sends these packets over the T1 WAN line, and sends other packets overthe Internet. This saves bandwidth on the more expensive serial interface.274 Administration of the Avaya G350 Media Gateway