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Tracing Layer 2 VPN Traffic and Operations

To trace Layer 2 VPN protocol traffic, you can specify options in the Layer 2 VPN traceoptions statement:




traceoptions {
file filename <replace> <size size> <files number> <no-stamp>
<world-readable | no-world-readable>;
flag flag <flag-modifier> <disable>;
}

You can configure the traceoptions statement at the following hierarchy levels:

[edit routing-instances routing-instance-name protocols l2vpn]
[edit logical-systems logical-system-name routing-instances routing-instance-name protocols l2vpn]

The following trace flags display the operations associated with Layer 2 VPNs:

all—All Layer 2 VPN tracing options.
connections—Layer 2 connections (events and state changes).
error—Error conditions.
general—General events.
nlri—Layer 2 advertisements received or sent by means of the BGP.
normal—Normal events.
policy—Policy processing.
route—Routing information.
state—State transitions.
task—Routing protocol task processing.
timer—Routing protocol timer processing.
topology—Layer 2 VPN topology changes caused by reconfiguration or advertisements received from other PE routers using BGP.

Disabling Normal TTL Decrementing for VPNs

To diagnose networking problems related to VPNs, 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 you are 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 MPLS Applications Configuration Guide.

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