Chapter 21: Configuring Policy-Based Routing - Avaya G250 Administration

Chapter 21: Configuring policy-based
Policy-based routing allows you to configure a routing scheme based on traffic's source IP
address, destination IP address, IP protocol, and other characteristics. You can use
policy-based routing (PBR) lists to determine the routing of packets that match the rules defined
in the list. Each PBR list includes a set of rules, and each rule includes a next hop list. Each next
hop list contains up to 20 next hop destinations to which the G250/G350 sends packets that
match the rule. A destination can be either an IP address or an interface.
Policy-based routing takes place only when the packet enters the interface, not when it leaves.
Policy-based routing takes place after the packet is processed by the Ingress Access Control
List and the Ingress QoS list. Thus, the PBR list evaluates the packet after the packet's DSCP
field has been modified by the Ingress QoS List. See
Packets on page 537.
Note:
The Loopback 1 interface is an exception to this rule. On the Loopback 1
Note:
interface, PBR lists are applied when the packet leaves the interface. This
enables the PBR list to handle packets sent by the G250/G350 device itself, as
explained below.
Note:
ICMP keepalive provides the interface with the ability to determine whether a next
Note:
hop is or is not available. See
Policy-based routing only operates on routed packets. Packets traveling within the same subnet
are 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 the
G250/G350 itself. This includes ping packets to or from the G250/G350, as well as telnet, FTP,
DHCP Relay, TFTP, HTTP, NTP, SNMP, H.248, and other types of traffic. The Loopback
interface is also used for 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 if
you want to route specific packets generated by the G250/G350 to a specific next-hop.
Unlike the case with other interfaces, PBR lists on the Loopback interface are applied to
packets when they leave the G250/G350, rather than when they enter.
routing
ICMP keepalive
Figure 51: Applying Policy Lists to
on page 252.
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