When path protection is configured, the near-end router keeps the protect path in a warm standby state. This allows it to quickly transition to the protect path if the working path is down.

The candidate-paths parameter is set to dynamic->pcep to enable SR-PCE delegation. The dynamic computation uses standard metrics, including traffic engineering, IGP, and latency.

Paths with higher preference values are chosen over those with lower preference values.

Note

You must always set the protect path with a lower preference value.

A third candidate path with a preference lower than 100 can be defined as a restoration path. This path is not pre-signaled and must be configured with backup-ineligible. While the restoration path does not have a disjoint-path ID, it uses a bidirectional association ID that matches the reverse policy.

The lock-duration parameter determines the reversion behavior. When a higher-preference path becomes available, the policy switches to it after the lock-duration expires. By default, the lock-duration is set to 300 seconds. Setting the value to 0 disables dynamic reversion.

Circuit-style uses the segments constraints of unprotected-only and adjacency-sid-only. If manual adjacency-SIDs are configured, they are used; otherwise, dynamic adjacency-SIDs are used. It is recommended to configure manual adjacency-SIDs.

The group-id for the disjoint-path must be identical on both the active and backup paths. Additionally, the group-id must be unique among nodes that use the same SR-PCE

The co-routed association ID must be the same for both bidirectional active and backup paths.

The policy uses the previously defined liveness profile named liveness-check.

The SR Policy table lists all the CS SR-TE policies.

The Circuit Style Policy Details window is displayed in the side panel. By default, the active path is displayed and shows the bidirectional paths (Bi-Dir Path checkbox is selected) on the topology map.

If the bandwidth of a new policy exceeds bandwidth pool size, the policy goes down. The requested bandwidth is set to the configured bandwidth, but the reserved bandwidth becomes zero.

If an existing policy is configured with a bandwidth that exceeds the bandwidth pool size, the policy remains up, but the reserved bandwidth stays at its previous value.

The sample output displays a policy's requested bandwidth and current bandwidth.

RP/0/RP0/CPU0:ron-ncs57c3-1#show segment-routing traffic-eng policy color 119
Thu May 4 09:01:57.797 PDT

SR-TE policy database
---------------------

Color: 119, End-point: 10.0.0.44
Name: srte_c_119_ep_10.0.0.44
Status:
Admin: up Operational: up for 11:46:42 (since May 3 21:15:14.898)
Candidate-paths:
Preference: 200 (configuration) (active)
Name: dynamic-cs-srte-to-55a2-p2
Requested BSID: dynamic
PCC info:
Symbolic name: cfg_dynamic-cs-srte-to-55a2-p2_discr_200
PLSP-ID: 7
Constraints:
Protection Type: unprotected-only
Maximum SID Depth: 12
Adjacency SIDs Only: True
Dynamic (pce 201.0.0.106) (valid)
Metric Type: IGP, Path Accumulated Metric: 20
SID[0]: 15739 [Adjacency-SID, 10.139.1.1 - 10.139.1.2]
SID[1]: 15720 [Adjacency-SID, 10.1.26.0 - 10.1.26.1]
Reverse path:
SID[0]: 15227 [Adjacency-SID, 10.1.26.1 - 10.1.26.0]
SID[1]: 15727 [Adjacency-SID, 10.139.1.2 - 10.139.1.1]
Protection Information:
Role: WORKING
Path Lock: Timed
Lock Duration: 300(s)
State: ACTIVE
Preference: 100 (configuration) (protect)
Name: dynamic-cs-srte-to-55a2-p2
Requested BSID: dynamic
PCC info:
Symbolic name: cfg_dynamic-cs-srte-to-55a2-p2_discr_100
PLSP-ID: 6
Constraints:
Protection Type: unprotected-only
Maximum SID Depth: 12
Adjacency SIDs Only: True
Dynamic (pce 201.0.0.106) (valid)
Metric Type: IGP, Path Accumulated Metric: 30
SID[0]: 15734 [Adjacency-SID, 10.1.42.0 - 10.1.42.1]
Reverse path:
SID[0]: 15523 [Adjacency-SID, 10.1.42.1 - 10.1.42.0]
Protection Information:
Role: PROTECT
Path Lock: Timed
Lock Duration: 300(s)
State: STANDBY
Attributes:
Binding SID: 24047
Forward Class: Not Configured
Steering labeled-services disabled: no
Steering BGP disabled: no
IPv6 caps enable: yes
Bandwidth Requested: 35.000 Gbps
Bandwidth Current: 35.000 Gbps
Invalidation drop enabled: no
Max Install Standby Candidate Paths: 0

The same Pseudowire class can be used for multiple PLE services between the same far-end routers, or a unique class can be used for each service. The Pseudowire class defines the underlying transport for the service. In this case, the transport is MPLS, using a specific SR-TE policy. The pw-class command is followed by a user-defined name. In this example, the name is circuit-style-srte.

The preferred-path is the circuit-style policy used to configure an explicit MPLS path for the L2VPN service. In this case, the preferred-path is set to the SR-TE policy created from the source node to the 10.0.0.42 endpoint node. The path refers to the computed name of the policy, not the configured name.

The xconnect group command is used to administratively group similar L2VPN services and can be set to any user-defined value.

This interface is the CEM interface type for PLE.

The user-defined evi value must be the same on each far-end router. The target must match the source value configured on the remote endpoint.