H3C Technologies H3C S12500 Series Switches - Manual (Page 286)

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Configuring policy-based routing
Introduction to policy-based routing
What is policy-based routing
Policy-based routing (PBR) is a routing mechanism based on user-defined policies. Different from the
traditional destination-based routing mechanism, PBR enables you to use a policy to route packets based
on the source address, packet length, and other criteria. You can specify the VPN instance, packet
priority, output interface, next hop, default output interface, default next hop, and other parameters to
guide the forwarding of packets that match specific ACLs or have specific lengths.
PBR involves local PBR and interface PBR:
• Local PBR applies to locally generated packets only, such as the ICMP packets generated by using
the ping command.
• Interface PBR applies to packets forwarded through the interface only.
In most cases, interface PBR is implemented to meet the forwarding and security requirements.
In general, PBR takes precedence over destination-based routing. PBR applies to the packets matching
the specified criteria, and other packets are forwarded through destination-based routing.
Policy
A policy that comprises one or multiple nodes is used to route IP packets.
Node
A node is identified by a node number. The smaller the node number is, the higher the priority of the
node is.
A policy node consists of if-match clauses and apply clauses. An if-match clause specifies a match
criterion on a node, while an apply clause specifies an action to be taken on packets.
The action to be taken on matched packets depends on the match mode, which can be permit or deny.
if-match clause
One type of if-match clauses is available: if-match acl.
You can specify only one if-match clause of each type in a policy node.
apply clause
PBR supports the following types of apply clauses in Table 9 .