F3215-HP Load Balancing Module Network Management Configuration Guide-6PW101

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Configuring policy-based routing
Overview
Different from destination-based routing, policy-based routing (PBR) uses user-defined policies to route
packets based on the source address, packet length, and other criteria. A policy can specify the output
interface, next hop, default output interface, default next hop, and other parameters for packets that
match specific criteria such as ACLs or have specific lengths.
A device uses PBR to forward matching packets and uses the routing table to forward other packets. If
PBR is not configured, a device uses the routing table to forward packets.
PBR falls into local PBR and interface PBR.
• Local PBR guides the forwarding of locally generated packets, such as the ICMP packets generated
by using the ping command.
• Interface PBR guides the forwarding of packets received on an interface only.
Policy
A policy comprises match criteria and actions to be taken on the matching packets. A policy can
comprise one or multiple nodes. The following describes information about nodes:
• Each node is identified by a node number. A smaller node number has a higher priority.
• A node comprises if-match and apply clauses. An if-match clause specifies a match criterion, and
an apply clause specifies an action.
• A node has a match mode of permit or deny.
A policy matches nodes in priority order against packets. If a packet satisfies the match criteria on a node,
it is processed by the action on the node. Otherwise, it goes to the next node for a match. If the packet
does not match the criteria on any node, it is forwarded according to the routing table.
if-match clause
PBR supports the following types of if-match clauses:
• if-match acl—Sets an ACL match criteria.
• if-match packet-length—Sets a packet length match criterion.
• if-match reverse-input-interface—Sets a reverse input interface match criterion. A response packet
matches the criterion if the specified reverse input interface is the interface that received the
corresponding request packet.
You can specify multiple if-match clauses for a node, but only one if-match clause can be specified for
each type at most. To match a node, a packet must satisfy all the if-match clauses of the node.
apply clause
PBR supports the following types of apply clauses, as shown in Table 28. You can specify multiple apply
clauses for a node, but some of them might not be executed.