MPLS TE Path Protection
Table of Contents
Introduction
MPLS TE Path Protection, provides resiliency for the whole path.
MPLS TE Path Protection
- Protection of a TE path is provided end to end.
- Primary is the regular LSP, while protected is the backup LSP.
- Accomplished using a primary and a protected tunnel. Both tunnels are signaled, including protected to minimize on the failover time.
- Failover is triggered by a RSVP Error message sent to the LSP head end. Once the head end received this error message, it switches over to the secondary tunnel. The major problem is time it takes to receive the RSVP Error message. The switchover is non-deterministic based on the arrival of the RSVP message and CPU processing of it.
- Primary and protected tunnels should take difference path, which might be harder to ensure when Inter-Area or Inter-Domain boundary.
- Twice as much resources are used with the secondary requesting the same bandwidth as primary and still being idle.
- Dynamic path-options are not supported only explicit.
- Sample configuration under the tunnel:
- tunnel mpls traffic-eng path-option protect 5 explicit name backup-tun219
- Make sure that the primary path-option is 5 as well.
- You can have multiple protect option for primary, up to 8. See the path-option list command below.
- Make sure to configure the same attributes or bandwidth requirements on the protected option.
Path Protection Example
- The following example has a tun219 configured between R2 and XR1.
- The primary path is via R2-R4-R5-XR1.
- The protected path (backup path) is via R2-R3-R6-XR1.
Relevant Commands
tunnel mpls traffic-eng path-option protect
Command used to configure the protect LSP for primary LSP.
ID is path option index to protect.
R1(config-if)# tunnel mpls traffic-eng path-option protect (id) explicit name (explicit-listname)
tunnel mpls traffic-eng path-option protect list
Command used to configure the protect LSP for primary LSP.
ID is path option index to protect.
Path-option list name should be configured to aggregate path-options in an order.
R1(config-if)# tunnel mpls traffic-eng path-option protect (id) list name (pathoption-listname)
mpls traffic-eng path-option name
Creates a list of path-options. This list could be used to create up to 8 protected paths (backups) for the primary path.
R1(config)# mpls traffic-eng path-option list name (name)
R2(cfg-pathoption-list)# path-option (id) explicit name (name-a)
R2(cfg-pathoption-list)# path-option (id) explicit name (name-b)
show mpls traffic-eng path-option list
R1# show mpls traffic-eng path-option list
Additional Resources
MPLS Traffic Engineering - Path Protection - Cisco