Description

"Invalid interface" counter in the PFE statistics traffic output is increasing.

Symptoms

The PFE statistics traffic output shows an increasing count of "Invalid interface".

user@router> show pfe statistics traffic   
<..>
Packet Forwarding Engine hardware discard statistics:
<..> 
    Invalid interface          :                12485
    Info cell drops            :                    0
    Fabric drops               :                    0
    Unicast EAPOL              :                    0
<..>

Solution

"Invalid interface" counter increases when a packet with VLAN ID X is received on an interface with vlan-tagging enabled. And this VLAN ID X is not configured on the interface.
Several scenarios where this can be seen:

Scenario 1:

The incoming packets are ARP requests received on an interface with an unconfigured VLAN ID.
As a result, the packets are dropped due to an "unknown iif" or "invalid interface."

Scenario 2:

The incoming packets are LLDP packets that are sent from the remote device. The device receives the LLDP packets on non-LLDP interfaces tagged interfaces (vlan-tagging is enabled).
These LLDP packets are dropped and counted as "unknown iif" or "Invalid interface."

 

To capture packets which are dropped with "Invalid interface" reason, please contact JTAC.

Modification History

2024-04-03: Article Created
2024-05-14: Added the LLDP scenario

2024-11-11: Reworked the article, improved readability.