497
•
Static
mode
—You manually specify the local and remote discriminators through command
lines to establish the BFD session.
•
Dynamic
mode
—The system automatically runs MPLS ping to negotiate the discriminators to
establish the BFD session.
In static mode, the egress node returns a BFD control packet to the ingress node through the reverse
tunnel. If no reverse tunnel exists, the ingress node cannot receive the BFD control packet, resulting
in a verification failure.
In dynamic mode, the egress node returns a BFD control packet to the ingress node through the
reverse tunnel. If no reverse tunnel exists, the egress mode returns a BFD packet through IP routing.
Use the static mode to test the connectivity of a pair of LSPs or MPLS TE tunnels in opposite
directions between two devices. Use the dynamic mode to test the connectivity of one LSP or MPLS
TE tunnel from the local device to the remote device.
A PW is bidirectional. You will get the correct result using either the static or dynamic mode.
Periodic MPLS tracert
The periodic MPLS tracert feature automatically traces an LSP tunnel at intervals. It locates errors on
the LSP tunnel, verifies the consistency of the data plane and control plane, and records the
detected errors in system logs. You can check the logs to monitor LSP connectivity.
If both BFD and periodic MPLS tracert are configured for an LSP, and the periodic tracert feature
detects a data plane and control plane inconsistency, the device performs the following tasks:
1.
Deletes the BFD session for the LSP.
2.
Re-establishes the BFD session based on the control plane.
Protocols and standards
•
RFC 4379,
Detecting Multi-Protocol Label Switched (MPLS) Data Plane Failures
•
RFC 5085,
Pseudowire Virtual Circuit Connectivity Verification (VCCV): A Control Channel for
Pseudowires
•
RFC 5885,
Bidirectional Forwarding Detection (BFD) for the Pseudowire Virtual Circuit
Connectivity Verification (VCCV)
Configuring MPLS OAM for LSP tunnels
To verify LSP connectivity, you can use one of the following methods:
•
Use the
ping mpls ipv4
command or the
tracert mpls ipv4
command to trigger LSP
connectivity verification as needed.
•
Configure BFD or periodic MPLS tracert for the system to automatically verify LSP connectivity.
Configuring MPLS ping for LSPs
Perform the following task in any view: