Configuring pbr, Introduction to pbr, Policy – H3C Technologies H3C S12500-X Series Switches User Manual
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Configuring PBR
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Introduction to PBR
Policy-based routing (PBR) uses user-defined policies to route packets. A policy can specify the next hop
and other parameters for packets that match specific criteria such as ACLs.
A device forwards received packets using the following process:
1.
The device uses PBR to forward matching packets.
2.
If the packets do not match the PBR policy or the PBR-based forwarding fails, the device uses the
routing table, excluding the default route, to forward the packets.
3.
If the routing table-based forwarding fails, the device uses the default next hop or default output
interface defined in PBR to forward packets.
4.
If the default next hop or default output interface-based forwarding fails, the device uses the default
route to forward packets.
PBR includes 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.
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Policy
A policy comprises match criteria and actions to be taken on the matching packets. A policy can have
one or multiple nodes as follows:
•
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 matches the 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.
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if-match clause
PBR supports only the if-match acl clause to set the ACL match criterion.
You can specify only one if-match clause for a node.
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apply clause
PBR supports only the apply next-hop clause to set the next hop for packets.