[SRX] False increment of L2 channel errors on interface ge-0/0/0 on branch devices

Summary:

In branch devices running Junos 12.3X48, it is observed that L2 channel error incorrectly increments on ge-0/0/0 interface under following conditions:

The ge-0/0/0 is configured with a unit of 0
ge-0/0/0 is in "up up" state in the output of "show interfaces terse"
It is NOT necessary for ge-0/0/0 to actively carry traffic
Dynamic Routing protocol (especially of broadcast/multicast nature) is running on a VLANL tagged interface

Note: ge-0/0/0 interface is NOT a part of the above mentioned VLAN traffic.

If the ge-0/0/0 is a part of VLAN or these errors are seen on any other interface except ge-0/0/0, please refer to KB24550 - [SRX] How to troubleshoot incrementing L2 channel errors on the interface

Symptoms:

L2 channel error increment is typically validated via ">show interfaces ge-0/0/0 extensive" output on ge-0/0/0 interface without any actual traffic and only an active IFL (sub-interface).

root> show interfaces ge-0/0/0 extensive | match L2 ;

Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 7721, L2 mismatch timeouts: 0, FIFO errors: 0


root> show interfaces ge-0/0/0 extensive | match L2 

Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 7726, L2 mismatch timeouts: 0, FIFO errors: 0 
Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 7729, L2 mismatch timeouts: 0, FIFO errors: 0 

root> show interfaces ge-0/0/0 extensive | match L2 

Errors: 0, Drops: 0, Framing errors: 0, Runts: 0, Policed discards: 0, L3 incompletes: 0, L2 channel errors: 7733, L2 mismatch timeouts: 0, FIFO errors: 0

Cause:

This issue is caused by an internal switching loop triggered by VLAN interface(s) configured to participate on any dynamic protocol such as OSPF / BGP on SRX in question.
L2 channel error counter on ge-0/0/0 will increment with every periodic hello packet for configured dynamic protocol that is meant for participating vlan.x interfaces.

Solution:

This issue only affects SRX branch series running Junos 12.3X48. It is fixed beginning with Junos 12.3X48-D70. Please refer to PR1346691 - L2 Channel Errors might increase on the interface with specific VLAN configuration 42.

Knowledge Base