R2511-HP MSR Router Series Layer 3 - IP Routing Configuration Guide(V5)

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Configuring IPv6 PBR
Introduction to IPv6 policy-based routing
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 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.
Policy
An IPv6 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.
An IPv6 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
IPv6 PBR supports the following types of if-match clauses:
• if-match acl6—Sets an ACL match criteria.
• if-match packet-length—Sets an IPv6 packet length match criterion.
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
IPv6 PBR supports the following types of apply clauses, as shown in Table 11. You can specify multiple
apply clauses for a node, but some of them might not be executed.
Table 11 Priorities and meanings of the apply clauses
Clause Meanin
g
Priorit
y
apply
ipv6-precedence
Sets an IP precedence. If configured, this clause will always be executed.