H3C Technologies H3C S10500 Series Switches - Manual (Page 182)

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NOTE:
•
You can associate a nonexistent track entry with a static route. The association takes effect only after you
use the track command to create the track entry.
• If the track module detects the next hop accessibility of the static route in a private network through
NQA, the VPN instance name of the next hop of the static route must be consistent with that configured
for the NQA test group. Otherwise, the accessibility detection cannot function properly.
• If a static route needs route recursion, the associated track entry must monitor the next hop of the
recursive route instead of that of the static route; otherwise, a valid route may be considered invalid.
• For more information about static route configuration, see Layer 3—IP Routing Configuration Guide.
Associating track with PBR
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 (based on the source
address and other criteria) to route packets.
PBR cannot detect the availability of any action taken on packets. When an action is not available,
packets processed by the action may be discarded. For example, configure PBR to forward packets that
match certain criteria through a specific next hop. When the specified next hop fails, PBR cannot sense
the failure, and continues to forward matching packets to the next hop.
This problem can be solved by associating track with PBR, which improves the flexibility of 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:
• Next hop
• 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
Follow these steps to associate track with PBR:
To do… Use the command… Remarks
Enter system view system-view —
Create a policy or policy node
and enter PBR policy node view policy-based-route policy-name [ deny |
permit ] node node-number
Required