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Too many output drops

I notice too many output drops on my router's multilink interface. What does this mean and what could be causing this?

Software Version: c3745-ipvoicek9-mz.124-10b.bin

Problem Details: 3745#sh int multilink 1

Multilink1 is up, line protocol is up

Hardware is multilink group interface

MTU 1500 bytes, BW 3072 Kbit, DLY 100000 usec,

reliability 255/255, txload 31/255, rxload 8/255

Encapsulation PPP, LCP Open, multilink Open

Listen: CDPCP

Open: IPCP, loopback not set

Keepalive set (10 sec)

DTR is pulsed for 2 seconds on reset

Last input 00:00:08, output never, output hang never

Last clearing of "show interface" counters 3w0d


Input queue: 0/75/0/0 (size/max/drops/flushes); Total output drops: 510015


Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 97000 bits/sec, 128 packets/sec

5 minute output rate 384000 bits/sec, 144 packets/sec

97055282 packets input, 2198805340 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

100573061 packets output, 2464703235 bytes, 0 underruns

0 output errors, 0 collisions, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

0 carrier transitions


Re: Too many output drops


In the absence of any other errors it looks like a simple case of over-subscription. The number doesn't mean much by itself, you need to look at it as a percentage, and in your case it's 0.5%

This may be OK, or it may be causing you issues already but without more context it's hard to say.



New Member

Re: Too many output drops

Thanks Andrew!

I am going to try increasing the output queue to 128.

Re: Too many output drops


Before you do that you might want to read the following doc which gives some more detailed info on troubleshooting output drops:

Enabling WRED on the interface could give you a better solution, but bear in mind that you probably won't be able to eliminate the drops, only manage them better.



New Member

Re: Too many output drops

Thanks for the link Andrew.

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