Input errors and low reliability in interface Vlan

Unanswered Question
Jul 8th, 2008

Hi everybody,

I'm having this problem, i have some switch in my network that have been having some problems with administration. In order to manage the devices i use the vlan 1 and just for that. When i checked the status of the interface vlan 1 on those switches that are having the problem i found that the reliability is low and that i have alot of input errors on the interface, here i show you:

sh int vlan1

Vlan1 is up, line protocol is up

Hardware is CPU Interface, address is 0007.8437.2b40 (bia 0007.8437.2b40)

Internet address is

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

reliability 128/255, 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 never, output hang never

Last clearing of "show interface" counters 07:27:45

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

Queueing strategy: fifo

Output queue: 0/40 (size/max)

5 minute input rate 10000 bits/sec, 160 packets/sec

5 minute output rate 5000 bits/sec, 6 packets/sec

4265824 packets input, 32209176 bytes, 0 no buffer

Received 332 broadcasts (0 IP multicast)

0 runts, 0 giants, 266608 throttles

3777829 input errors, 0 CRC, 0 frame, 0 overrun, 9960 ignored

192675 packets output, 16684602 bytes, 0 underruns

0 output errors, 0 interface resets

0 output buffer failures, 0 output buffers swapped out

I already checked the status of the interfaces that are trunk between those switch and there are not input errors or you have any suggestion to find out what is going on???

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Overall Rating: 5 (1 ratings)
Mark Yeates Tue, 07/08/2008 - 15:09

What kind of switch is this? The main error that you are having are throttles. Throttles are generally caused by congestion on the interface. I would recommend upgrading the switch because the amount of errors generated over such a small period of time is pretty extensive. You could also try to distribute the traffic over multiple VLAN's. I would also assume that you are having serious performance issues as well.


alfonso.cornejo Tue, 07/08/2008 - 15:32

Hi Mark!

The switch are WS-C2950-24 and we are having problems just with the int vlan 1, i mean when i ping that ip address we have very hight times and if we ping another device that is connected on a different vlan on a port on this switch and the times are fine

Mark Yeates Tue, 07/08/2008 - 18:33

I am curious as to why your VLAN interface is processing that much traffic. How many interfaces are connected and using VLAN 1? The bottom line is that your switch is over utilized.


alfonso.cornejo Wed, 07/09/2008 - 06:32

Hi Mark,

There are two trunk interfaces in the switch wich are connected to two different switch, those interfaces don't have input errors and are not with too much traffic (like 1 or 2 Mbps and are interfaces 100Mbps)...

Thanks alot


alfonso.cornejo Thu, 07/10/2008 - 06:55

Hi Everydoby,

I found the solution, the problem is related with the bug CSCea23138:

Input errors on management vlan with vlan mismatch on trunk

When you connect the 2950 via a trunk to other switches and if the number of

VLANs on the 2950 is lower than the number on the connected switch, you may

see 'input errors' on the management VLAN interface of the 2950 when you

issue "show interface".

The workaround is to match the vlans configured on either side of the trunk

link. This stops the errors.

It is not solve in the latest version wich is 12.1(22)EA10a

Best regards,


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