Configuring CR-LSP Backup
Pre-configuration Tasks
CR-LSP backup provides an end-to-end protection mechanism. If a primary CR-LSP fails, traffic rapidly switches to a backup CR-LSP, ensuring uninterrupted traffic transmission.
- Configure a dynamic MPLS TE or DS-TE tunnel. For details, see Configuring a Dynamic MPLS TE Tunnel or Configuring a Dynamic DS-TE Tunnel.
- Enable MPLS, MPLS TE, and RSVP-TE globally and on interfaces of each node along a backup CR-LSP.
NOTE: If CR-LSP hot standby is configured, perform the operation of Configuring Static BFD for CR-LSPs or Configuring Dynamic BFD for CR-LSPs to implement fast switching at the millisecond level.
Creating a Backup CR-LSP
Context
CR-LSP backup can be configured to allow traffic to switch from a primary CR-LSP to a backup CR-LSP, providing end-to-end protection.
Perform the following configurations on the ingress node of an MPLS TE tunnel.
Procedure
- Run system-view
The system view is displayed.
- Run interface tunnel tunnel-number
The tunnel interface view is displayed.
- Run mpls te backup hot-standbympls te backup ordinary
or run:
The mode of establishing a backup CR-LSP is configured.
If hot-standby is specified, a hot-standby CR-LSP is set up. To implement fast switching at the millisecond level, perform the operation of Configuring Static BFD for CR-LSPs or Configuring Dynamic BFD for CR-LSPs.
NOTE:
A tunnel interface cannot be used for both a bypass tunnel and a backup tunnel. A protection failure will occur if the mpls te backup and mpls te bypass-tunnel commands are run on the tunnel interface, or if the mpls te backup and mpls te protected-interface commands are run on the tunnel interface. For details on how to create a bypass CR-LSP, see Configuring Manual TE FRR or Configuring Auto TE FRR.
After hot standby or ordinary backup is configured, the system selects a path for a backup CR-LSP. To specify a path for a backup CR-LSP, repeatedly perform one or more of steps 4 to 6. When hot standby is configured, repeatedly perform one or more of steps 7 to 9.
- (Optional) Run mpls te path explicit-path path-name secondary
An explicit path is specified for the backup CR-LSP.
Use a separate explicit path for the backup CR-LSP to prevent the backup CR-LSP from completely overlapping its primary CR-LSP. Protection will fail if the backup CR-LSP completely overlaps its primary CR-LSP.
The mpls te path explicit-path command can be run successfully only after an explicit path is set up by running the explicit-path path-name command in the system view, and the nodes on the path are specified.
- (Optional) Run mpls te affinity property properties [ mask mask-value ] secondary
The affinity property is configured for the backup CR-LSP.
By default, the affinity property used by the backup CR-LSP is 0x0 and the mask is 0x0.
- (Optional) Run mpls te hop-limit hop-limit-value secondary
The hop limit is set for the backup CR-LSP.
The default hop limit is 32.
- (Optional) Run mpls te backup hot-standby overlap-path
The path overlapping function is configured. This function allows a hot-standby CR-LSP to use links of a primary CR-LSP.
By default, the path overlapping function is disabled. If the path overlapping function is disabled, a hot-standby CR-LSP may fail to be set up.
After the path overlapping function is configured, the path of the hot-standby CR-LSP partially overlaps the path of the primary CR-LSP when the hot-standby CR-LSP cannot exclude paths of the primary CR-LSP.
- (Optional) Run mpls te backup hot-standby wtr interval
The WTR time for a switchback is set.
By default, the WTR time for switching traffic from a hot-standby CR-LSP to a primary CR-LSP is 10 seconds.
- (Optional) Run mpls te backup hot-standby mode { revertive [ wtr interval ] | non-revertive }
A revertive mode is specified.
By default, the revertive mode is used.
- Run mpls te commit
The configuration is committed.
(Optional) Configuring Forcible Switchover
Context
If a backup CR-LSP has been established and a primary CR-LSP needs to be adjusted, configure the forcible switchover function to switch traffic from the primary CR-LSP to the backup CR-LSP. After adjusting the primary CR-LSP, switch traffic back to the primary CR-LSP. This process prevents traffic loss during the primary CR-LSP adjustment.
Perform the following configurations on the ingress node of an MPLS TE tunnel.
Procedure
- Before adjusting a primary CR-LSP, perform the following
configurations.
- Run hotstandby-switch force
Traffic is switched to a backup CR-LSP.
To prevent traffic loss, check that a backup CR-LSP has been established before running the hotstandby-switch force command.
- Run hotstandby-switch force
- After adjusting the primary CR-LSP, perform the following
configurations.
(Optional) Configuring Dynamic Bandwidth for Hot-Standby CR-LSPs
Context
Hot-standby CR-LSPs are established using reserved bandwidth resources by default. The dynamic bandwidth function can be configured to allow the system to create a primary CR-LSP and a hot-standby CR-LSP with the bandwidth of 0 bit/s simultaneously.
The dynamic bandwidth protection function allows a hot-standby CR-LSP to obtain bandwidth resources only after the hot-standby CR-LSP takes over traffic from a faulty primary CR-LSP. If the primary CR-LSP fails, traffic immediately switches to the hot-standby CR-LSP with 0 bit/s bandwidth. The ingress node uses the make-before-break mechanism to reestablish a hot-standby CR-LSP. After the new hot-standby CR-LSP has been successfully established, the ingress node switches traffic to this CR-LSP and tears down the hot-standby CR-LSP with 0 bit/s bandwidth. If bandwidth resources are insufficient, the ingress node is unable to reestablish a hot-standby CR-LSP with the desired bandwidth, and therefore switches traffic to the hot-standby CR-LSP with 0 bit/s bandwidth, ensuring uninterrupted traffic transmission.
Perform the following configurations on the ingress node of an MPLS TE tunnel.
Procedure
- Run system-view
The system view is displayed.
- Run interface tunnel tunnel-number
The tunnel interface view is displayed.
- Run mpls te backup hot-standby dynamic-bandwidth
The dynamic bandwidth function is enabled for hot-standby CR-LSPs.
NOTE:
If a hot-standby CR-LSP has been established before the dynamic bandwidth function is enabled, the system uses the Make-Before-Break mechanism to establish a new hot-standby CR-LSP with the bandwidth of 0 bit/s to replace the existing hot-standby CR-LSP.
The undo mpls te backup hot-standby dynamic-bandwidth command can be used to disable the dynamic bandwidth function. This allows the hot-standby CR-LSP with no bandwidth to obtain bandwidth.
- Run mpls te commit
The configuration is committed.
(Optional) Configuring a Best-Effort Path
Context
A best-effort path is configured on the ingress node of a primary CR-LSP to take over traffic if both the primary and backup CR-LSPs fail.
Perform the following configurations on the ingress node of an MPLS TE tunnel.
Procedure
- Run system-view
The system view is displayed.
- Run interface tunnel tunnel-number
The tunnel interface view is displayed.
- Run mpls te backup ordinary best-effort
A best-effort path is configured.
NOTE:
A tunnel interface cannot be used for both a best-effort path and a manually configured ordinary backup tunnel. A protection failure will occur if the mpls te backup ordinary best-effort and mpls te backup ordinary commands are run on the tunnel interface.
To establish a best-effort path over a specified path, run either or both of step 4 and step 5.
- (Optional) Run mpls te affinity property properties [ mask mask-value ] best-effort
The affinity property of the best-effort path is configured.
By default, the affinity property used by the best-effort path is 0x0 and the mask is 0x0.
- (Optional) Run mpls te hop-limit hop-limit-value best-effort
The hop limit of the best-effort path is set.
The default hop limit is 32.
- Run mpls te commit
The configuration is committed.
Verifying the CR-LSP Backup Configuration
Procedure
- Run the display mpls te tunnel-interface [ tunnel tunnel-number ] command to check information about the tunnel interface.
- Run the display mpls te hot-standby state { all [ verbose ] | interface tunnel interface-number } command to check information about the hot-standby status.
- Run the display mpls te tunnel [ destination ip-address ] [ lsp-id ingress-lsr-id session-id local-lsp-id ] [ lsr-role { all | egress | ingress | remote | transit } ] [ name tunnel-name ] [ { incoming-interface | interface | outgoing-interface } interface-type interface-number ] [ te-class0 | te-class1 | te-class2 | te-class3 | te-class4 | te-class5 | te-class6 | te-class7 ] [ verbose ] command to check CR-LSP information.