I am working at a Customer site today. They have an MPLS circuit that is effectively 2 T1's bundled together on a 3800 series ISR.
We have been noticing some output drops when we do a sho interface. They are pretty excessive in light of the fact that we do not have alot of load on that interface, and the reliability of the interface is at 255/255.
Here is a sample output from the interface:
GAMPLSRTR01#sho int multi1
Multilink1 is up, line protocol is up
Hardware is multilink group interface
Internet address is X.X.X.X/30
MTU 1500 bytes, BW 3072 Kbit, DLY 100000 usec,
reliability 255/255, txload 126/255, rxload 26/255
Encapsulation PPP, LCP Open, multilink Open
Open: IPCP, loopback not set
Keepalive set (10 sec)
DTR is pulsed for 2 seconds on reset
Last input 00:00:10, output never, output hang never
Last clearing of "show interface" counters 00:02:21
Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 2946
Queueing strategy: fifo
Output queue: 22/40 (size/max)
30 second input rate 321000 bits/sec, 322 packets/sec
30 second output rate 1520000 bits/sec, 345 packets/sec
44962 packets input, 5045539 bytes, 0 no buffer
Received 0 broadcasts, 0 runts, 0 giants, 0 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort
53031 packets output, 35239499 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 output buffer failures, 0 output buffers swapped out
0 carrier transitions
This reading was taken just a minute or so after the interface counters were cleared.
What would be the most obvious causes of these drops, in light of the fact that we are not hammering our MPLS link?
Could it be our configured Class of Service Policies? What else could potentially cause these drops?
Thanks much. I am in desparate need to explain this today if possible and currently am not sure what is going on.