Input queue flushes

Unanswered Question
Jan 30th, 2007

I have a vlan interface on a 6513 that has shown a high level of input queue flushes. I am trying to understand the nature of what is causing this. I have included a few details below, and yes I have cleared the counters a week ago. I check this several times a day and these increment in bursts.

Vlan14 is up, line protocol is up

Hardware is EtherSVI, address is 000d.662d.fa80 (bia 000d.662d.fa80)

Description: 4th Floor Closet A

Internet address is

MTU 1500 bytes, BW 1000000 Kbit, DLY 10 usec,

reliability 255/255, txload 1/255, rxload 1/255

Encapsulation ARPA, loopback not set

ARP type: ARPA, ARP Timeout 04:00:00

Last input 00:00:00, output 00:00:07, output hang never

Last clearing of "show interface" counters 6d23h

Input queue: 0/75/698/698 (size/max/drops/flushes); Total output drops: 0

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 335000 bits/sec, 150 packets/sec

5 minute output rate 1189000 bits/sec, 194 packets/sec

L2 Switched: ucast: 17718 pkt, 4341606 bytes - mcast: 3471771 pkt, 855732428 bytes

L3 in Switched: ucast: 82294512 pkt, 27173808949 bytes - mcast: 0 pkt, 0 bytes mcast

L3 out Switched: ucast: 90072695 pkt, 70849844338 bytes mcast: 0 pkt, 0 bytes

85788885 packets input, 28030551254 bytes, 0 no buffer

Received 3471660 broadcasts, 0 runts, 0 giants, 0 throttles

0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored

90238780 packets output, 70507594890 bytes, 0 underruns

0 output errors, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

The physical interfaces are clean, just the vlan interface is showing the flushes. What do you think?

I have this problem too.
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lujohnso Tue, 01/30/2007 - 19:09

Drops/flushes on a VLAN interface indicate some level of traffic hitting the MSFC CPU meaning that some of your traffic is being software-switched. While this is normal for some traffic types (ARP, routing protocol packets, etc.) there was a point in time where there was not enough queue space to accommodate these packets. You can increase the input queue size to try and rectify this:

example: Switch(config-if)#hold-queue 2000 in

and/or do RP inband sniffer traces to see what traffic is being punted to the CPU.

Hope that helps.

Raja Rajan Fri, 09/16/2016 - 22:45

Hello All,

I am having interface flushes packet count as 5. Is it will cause any issue?.. And please some one help to resolve this flushes.

CHN003P2#sh int gi4/0/0 | in drops|errors
Input queue: 1/1024/0/5 (size/max/drops/flushes); Total output drops: 0
0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored
0 output errors, 0 collisions, 0 interface resets
0 unknown protocol drops




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