i have router 2951 and its Lan side too many drops on input queue:
Encapsulation ARPA, loopback not set
Keepalive set (10 sec)
Full Duplex, 1Gbps, media type is RJ45
output flow-control is XON, input flow-control is XON
ARP type: ARPA, ARP Timeout 04:00:00
Last input 00:00:00, output 00:00:00, output hang never
Last clearing of "show interface" counters 21:39:36
Input queue: 0/75/20783/0 (size/max/drops/flushes); Total output drops: 877
Queueing strategy: fifo
Output queue: 0/40 (size/max)
5 minute input rate 3006000 bits/sec, 2040 packets/sec
5 minute output rate 15714000 bits/sec, 2078 packets/sec
92383982 packets input, 25104737639 bytes, 0 no buffer
Received 3 broadcasts (0 IP multicasts)
0 runts, 0 giants, 7804 throttles
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 watchdog, 0 multicast, 0 pause input
96737602 packets output, 85709878748 bytes, 0 underruns
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops
0 babbles, 0 late collision, 0 deferred
1 lost carrier, 0 no carrier, 0 pause output
0 output buffer failures, 0 output buffers swapped out
I have 20mbs link but mostly "5 minute output rate 15714000 bits/sec" cannot reach the 20mbs
please anybody help out to troubleshoot this problem
the first thing you could try is to change the MTU size on your interface. Use the interface command 'ip tcp adjust-mss' and set it to 1452:
ip tcp adjust-mss 1452
or (depending on your IOS version):
ip mtu 1452
ip mtu 1480
and check if that makes a difference.
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Input queue drops might be indicative that the router cannot keep up with a high speed burst of ingress traffic.
As your CIR is 20 Mbps, you might see if you can run the physical line at 100 Mbps rather than gig.
I recall (?) there's some Cisco documentation that increasing the input queue size, even to its maximum setting, might avoid input queue drops while often not being adverse to the traffic or the functioning of the router.