The mpls te srlg path-calculation command configures an SRLG-based path calculation mode.
The undo mpls te srlg path-calculation command deletes an SRLG-based path calculation mode.
By default, when calculating a path, CSPF does not consider an SRLG constraint or check whether the primary CR-LSP and a Bypass CR-LSP or a hot-standby CR-LSP are in the same SRLG.
| Parameter | Description | Value |
|---|---|---|
| strict | Indicates that CSPF must calculate a bypass CR-LSP or
a hot-standby CR-LSP according to the SRLG attribute. The link that
the primary path uses and the link that the bypass CR-LSP or hot-standby
CR-LSP uses cannot be in the same SRLG. NOTE:
After you specify this parameter, all the links on the primary CR-LSP regardless of whether the SRLG attribute is configured cannot be used for calculation of the bypass or hot-standby CR-LSP. However, nodes on the primary CR-LSP can be used in CSPF calculation. |
- |
| preferred | Indicates that CSPF prefers the SRLG attribute the first
time it calculates a Bypass CR-LSP or hot-standby CR-LSP. If the initial
calculation fails, the CSPF does not use the SRLG attribute as a constraint. NOTE:
If no path calculation mode is specified in the mpls te srlg path-calculation command, SRLG-based path calculation is performed in preferred mode by default. |
- |
Usage Scenario
In the TE FRR or hot standby scenario, to enable CSPF to calculate a path for a Bypass CR-LSP or a hot-standby CR-LSP based on the SRLG attribute, you must run the mpls te srlg path-calculation command on the ingress of the tunnel.
The SRLG, like the bandwidth and affinity property, is a constraint in path calculation. If SRLG is configured for links and the mpls te srlg path-calculation command is configured on the ingress of the primary CR-LSP, when calculating the path of a Bypass CR-LSP or a hot-standby tunnel, CSPF determines whether the SRLG attribute is used as a constraint according to the configured SRLG calculation mode.
Precautions
If strict is configured, CSPF always considers SRLG as a constraint.
If preferred is configured, the first time that CSPF calculates a path is according to the SRLG attribute. If the calculation fails, CSPF tries to calculate again without considering SRLG.