Trace Layer 2 VPN Traffic and Operations

To trace Layer 2 VPN protocol traffic, you can specify options in the Layer 2 VPN traceoptions statement at the [edit routing-instances routing-instance-name protocols l2vpn] hierarchy level:

[edit routing-instances routing-instance-name protocols l2vpn]

traceoptions {

    file filename <replace> <size size> <files number> <nostamp>;

    flag flag <flag-modifier> <disable>;

}

The following trace flags display the operations associated with Layer 2 VPNs. Each can carry one or more of the following modifiers:

• all—All Layer 2 VPN tracing options
• connections—Layer 2 VPN connections (events and state changes)
• error—Error conditions
• nlri—Layer 2 VPN advertisements received or sent using BGP
• route—Trace routing information
• topology—Layer 2 VPN topology changes due to reconfiguration or due to advertisements received from other PE routers using BGP

Disable Normal TTL Decrementing for VPNs

To diagnose networking problems related to VPNs (Layer 2 or Layer 3), it can be useful to disable normal time-to-live (TTL) decrementing. In JUNOS, you can do this with the no-propagate-ttl and no-decrement-ttl statements. However, when tracing VPN traffic, only the no-propagate-ttl statement is effective.

For the no-propagate-ttl statement to have an effect on VPN behavior, you need to clear the PE-router-to-PE-router BGP session, or disable and then enable the VPN routing instance.

For more information about the no-propagate-ttl and no-decrement-ttl statements, see the JUNOS Internet Software Configuration Guide: MPLS Applications.