H3C Technologies H3C MSR 50 - Manual (Page 38)

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priority, outgoing interface, next hop, default outgoing interface, default next hop, and other parameters
to guide the forwarding of packets that match specific ACLs or have specific lengths.
PBR cannot detect the availability of any action taken on packets. When an action is not available,
packets processed by the action might be discarded. For example, configure PBR to forward packets that
match certain criteria through a specific interface. When the specified interface fails, PBR cannot sense
the failure, and continues to forward matching packets out of the interface.
This problem can be solved by associating Track with PBR, which improves the flexibility of the PBR
application and enables PBR to sense topology changes.
After you associate a track entry with an apply clause, the detection module associated with the track
entry sends the detection result of the availability of the object (an interface or an IP address) specified
in the apply clause.
• The Positive state of the track entry shows that the object is available, and the apply clause is valid.
• The Negative state of the track entry shows that the object is not available, and the apply clause is
invalid.
• The Invalid state of the track entry shows that the apply clause is valid.
The following objects can be associated with a track entry:
• Outgoing interface.
• Next hop.
• Default outgoing interface.
• Default next hop.
Configuration prerequisites
Before you associate Track with PBR, create a policy or a policy node and configure the match criteria as
well.
Configuration procedure
You can associate a nonexistent track entry with PBR. The association takes effect only after you use the
track command to create the track entry. For more information about PBR, see Layer 3—IP Routing
Configuration Guide.
To associate Track with PBR:
Step Command Remarks
44. Enter system view. system-view N/A
45. Create a policy or policy
node and enter PBR policy
node view.
policy-based-route policy-name [ deny |
permit ] node node-number
N/A
46. Define a match criterion.
• Define a packet length match criterion:
if-match packet-length min-len max-len
• Define an ACL match criterion:
if-match acl acl-number
Optional.
By default, no packets are
filtered.