Cisco Support Community
Showing results for 
Search instead for 
Did you mean: 

Welcome to Cisco Support Community. We would love to have your feedback.

For an introduction to the new site, click here. And see here for current known issues.

New Member

Input queue flushes

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?

New Member

Re: Input queue flushes

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.

New Member

Hello All,

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