Tracing LDP Protocol Traffic

The following sections describe how to configure the trace options to examine LDP protocol traffic:

• Tracing LDP Protocol Traffic at the Protocol and Routing Instance Levels
• Tracing LDP Protocol Traffic Within FECs
• Examples: Tracing LDP Protocol Traffic

Tracing LDP Protocol Traffic at the Protocol and Routing Instance Levels

To trace LDP protocol traffic, you can specify options in the global traceoptions statement at the [edit routing-options] hierarchy level, and you can specify LDP-specific options by including the traceoptions statement:

For a list of hierarchy levels at which you can include this statement, see the statement summary section for this statement.

Use the file statement to specify the name of the file that receives the output of the tracing operation. All files are placed in the directory /var/log. We recommend that you place LDP-tracing output in the file ldp-log.

The following trace flags display the operations associated with the sending and receiving of various LDP messages. Each can carry one or more of the following modifiers:

• address—Trace the operation of address and address withdrawal messages.
• binding—Trace label-binding operations.
• error—Trace error conditions.
• event—Trace protocol events.
• initialization—Trace the operation of initialization messages.
• label—Trace the operation of label request, label map, label withdrawal, and label release messages.
• notification—Trace the operation of notification messages.
• packet—Trace the operation of address, address withdrawal, initialization, label request, label map, label withdrawal, label release, notification, and periodic messages. This modifier is equivalent to setting the address, initialization, label, notification, and periodic modifiers.
• path—Trace label-switched path operations.
• periodic—Trace the operation of hello and keepalive messages.
• route—Trace the operation of route messages.
• state—Trace protocol state transitions.

Tracing LDP Protocol Traffic Within FECs

You can trace LDP protocol traffic within a specific FEC. You can filter LDP trace statements based on a FEC. The following trace flags are available for this purpose: route, path, and binding.

The following example illustrates how you might configure the LDP traceoptions statement to filter LDP trace statements based on a FEC:

This feature has the following limitations:

• The filtering capability is only available for FECs composed of IP version 4 (IPv4) prefixes.
• Layer 2 circuit FECs cannot be filtered.
• When you configure both route tracing and filtering, MPLS routes are not displayed (they are blocked by the filter).
• Filtering is determined by the policy and the configured value for the match-on option. When configuring the policy, be sure that the default behavior is always reject.
• The only match-on option is fec. Consequently, the only type of policy you should include is a route-filter policy.

Examples: Tracing LDP Protocol Traffic

Trace LDP path messages in detail:

Trace all LDP outgoing messages:

Trace all LDP error conditions:

Trace all LDP incoming messages and all label-binding operations: