Maybe this answers your question (from the documentation):
Configure the Dynamic LSP Metric
If no specific metric is configured, an LSP attempts to track the IGP
metric toward the same destination (the to address of the LSP).
IGP includes OSPF, IS-IS, RIP, and static routes. BGP and other RSVP/LDP
routes are excluded.
For example, if the OSPF metric toward a router is 20, all LSPs toward
that router automatically inherit metric 20. If the OSPF toward a
router later changes to a different value, all LSP metrics change
accordingly. If there are no IGP routes toward the router, the LSP
raises its metric to 65,535.
Note that in this case, the LSP metric is completely determined by IGP;
it bears no relationship to the actual path the LSP is currently
traversing through. If LSP reroutes (such as through reoptimization),
its metric doesn't change, and thus it remains transparent to
users. Dynamic metric is the default behavior; no configuration is
required.
Configure the Static LSP Metric
You can manually assign a fixed metric value to an LSP. Once configured
using the metric statement at the [edit protocols mpls
label-switched-path lsp-name ] hierarchy level, the LSP metric is fixed
and will not change:
[edit protocols mpls label-switched-path lsp-name]
metric number;
The LSP metric has several uses:
When there are parallel LSPs with the same egress router, the
metrics are compared to see which LSP has the lowest metric
value (the lowest cost) and therefore the preferred path to the
destination. If the metrics are the same, the traffic is shared.
Adjusting the metric values can force traffic to prefer some LSPs
over others, regardless of the underlying IGP metric.
When an IGP shortcut is enabled (see IGP Shortcuts), an IGP route
might be installed in the routing table with an LSP as the
next hop, if the LSP is on the shortest path to the destination. In
this case, the LSP metric is added to the other IGP metrics to
determine the total path metric. For example, if an LSP whose
ingress router is X and egress router is Y is on the shortest path
to destination Z, the LSP metric is added to the metric for the IGP
route from Y to Z to determine the total cost of the path. If
several LSPs are potential next hops, the total metrics of the
paths are compared to determine which path is preferred (that is,
has the lowest total metric). Or, IGP paths and LSPs leading to the
same destination could be compared using the metric value
to determine which path is preferred.
By adjusting the LSP metric, you can force traffic to prefer LSPs,
to prefer the IGP path, or to share the load among them.
If router X and Y are BGP peers, and if there is an LSP between
them, the LSP metric represents the total cost to reach Y from
X. If for any reason the LSP reroutes, the underlying path cost
might change significantly, but X's cost to reach Y remains the
same (the LSP metric), which allows X to report through BGP MED a
stable metric to downstream neighbors. As long as Y
remains reachable through the LSP, no changes are visible to
downstream BGP neighbors.
Thanks,
..Aviva
In message <001e01c0ccbf$af8199a0$3e64600a@2000bj.prosten.com>you write:
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> Hi all:
> could you tell me the function of LSP metric? Is it load-balance or =
> something like that?
>
> br
> shawn
>
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> <DIV><FONT face=3DArial size=3D2>Hi all:</FONT></DIV>
> <DIV><FONT face=3DArial size=3D2> could you tell me =
> the function of=20
> LSP metric? Is it load-balance or something like that?</FONT></DIV>
> <DIV><FONT face=3DArial size=3D2></FONT> </DIV>
> <DIV><FONT face=3DArial size=3D2>br</FONT></DIV>
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