Description

Packets/Drops are seen in the PFE Chassis queue for interface that are down/not configured on 4x 1GE (LAN), IQ2E PIC. This article explains this behavior.

Symptoms

Packets/Drops are seen in the PFE Chassis queue for interface down/not configured on 4x 1GE(LAN), IQ2E PIC.

Solution

On the PIC (4x 1GE IQ2E), the statistics shown for the Packet Forwarding Engine Chassis Queues represent a cumulative total or all four ports in the PIC. Customers may see this even if the interface is not configured or is physically down.

Topology

                                OSPF
1.1.1.1 R1 -----------<ge-0/0/0> R2 <ge-0/0/2>-------------- R3 3.3.3.3
10.1.1.1                                                     20.1.1.1

Note: On R2, <ge-0/0/1> status is Physical Down *

R2> show chassis hardware detail 
Hardware inventory:

FPC 0 E-FPC
PIC 0 REV 06 750-024781 AABM7878 4x 1GE(LAN), IQ2E <<<<<< 
Xcvr 0 REV 01 740-031980 AHP0JU2 SFP-SX
Xcvr 2 REV 02 740-011613 PH51QAP SFP-SX

[edit]
lab# run show interfaces terse |match ge             
ge-0/0/0                up    up
ge-0/0/0.0              up    up   inet     10.1.1.2/30  <<<<  towards R1   
ge-0/0/1                up    down
ge-0/0/2                up    up
ge-0/0/2.0              up    up   inet     20.1.1.2/30  << towards R3
ge-0/0/3                up    down

Clearing the statistics on the PIC to confirm the behavior.

Note: Only 2 interfaces are up on IQ2E PIC.

R2> clear interfaces statistics ge-0/0/0*

R2> clear interfaces statistics ge-0/0/1 

R2> clear interfaces statistics ge-0/0/2* 

R2> clear interfaces statistics ge-0/0/3 


lab# show interfaces ge-0/0/1    <<<<< not configured

Ping from R1 loopback to R3 loopback:

[edit]
lab@1# run ping 3.3.3.3 rapid count 5632    
PING 3.3.3.3 (3.3.3.3): 56 data bytes
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Check Packet Forwarding Engine Chassis Queues counters for PIC IQ2E interfaces: i.e. ge-0/0/0 and ge-0/0/1

lab# run show interfaces queue ge-0/0/0   << configured interface 

Packet Forwarding Engine Chassis Queues:     
Queues: 8 supported, 4 in use
Queue: 0, Forwarding classes: best-effort 
  Queued:
    Packets              :                  5632                     0 pps     <<<<< Packet Forwarding Engine Chassis Queues
    Bytes                :                473088                     0 bps
    Tail-dropped packets :                     0                     0 pps
    RED-dropped packets  :                     0                     0 pps
     Low, non-TCP        :                     0                     0 pps
     Low, TCP            :                     0                     0 pps
     High, non-TCP       :                     0                     0 pps
     High, TCP           :                     0                     0 pps
    RED-dropped bytes    :                     0                     0 bps
     Low, non-TCP        :                     0                     0 bps
     Low, TCP            :                     0                     0 bps
     High, non-TCP       :                     0                     0 bps
     High, TCP           :                     0                     0 bps


lab# run show interfaces queue ge-0/0/1 <<<< not a configured interface 

Packet Forwarding Engine Chassis Queues:
Queues: 8 supported, 4 in use
Queue: 0, Forwarding classes: best-effort 
  Queued:
    Packets              :                  5632                     0 pps    <<<< cumulative total for all 4 ports
    Bytes                :                473088                     0 bps                 
  Transmitted:
    Packets              :                  5632                      0 pps
    Bytes                :                473088                     0 bps
    Tail-dropped packets :                     0                     0 pps
    RED-dropped packets  :                     0                     0 pps
     Low, non-TCP        :                     0                     0 pps
     Low, TCP            :                     0                     0 pps
     High, non-TCP       :                     0                     0 pps
     High, TCP           :                     0                     0 pps
    RED-dropped bytes    :                     0                     0 bps
     Low, non-TCP        :                     0                     0 bps
     Low, TCP            :                     0                     0 bps
     High, non-TCP       :                     0                     0 bps
     High, TCP           :                     0                     0 bps

Therefore, on the PIC (4x 1GE IQ2E) the statisics shown for the Packet Forwarding Engine Chassis Queues represents a cumulative total for all four ports in the PIC.