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Undersized Frame Issue

jcvassmer
Level 1
Level 1

I have a 3400ME 12CS 4SFP Metro switch connected to a 7606 Cisco router via a dot1q trunk port. On the 3400's port facing the 7606 I receive valid but too small of frames (or undersized frames). The 7606 shows RCV-errs because of the Input queue show that it has dropped numerous packets. I have tried new x-over cables, different ports on both devices, and changing from forced 100, full duplex to auto negotiate. I am getting stumped, I have setups like this in other locations and have compared configs with clean ones and nothing seems to be out of sorts. Any suggestions?

5 Replies 5

htarra
Level 4
Level 4

This might indicate that this port is trunking dot1q and is receiving 64byte frames (including dot1q header).

Only impact should be that the counter increments. I think you have fixed the limit for queue. If it wills exceeded this no. it will drop the packet.

agtmcgarry
Level 1
Level 1

Thanks to both of your responses I appreciate it. I replaced the 3400ME with a catalyst 3560 and the problem continued. The MTU sizes have been set to 1518 actually, and the problem continues.

How is your trunk setup?

mode trunk or mode desirable? If mode trunk then switchport nonegotiate.

I had a similiar problem running an lacp etherchannel trunk. I switched it to mode on and it fixed the problem, but I'm guessing your running a normal non ec single link trunk?

Here is the 7606 (WS-X6548-RJ-45) phy port config. It is set to trunk mode on as well is the 3400 trunk interface.

interface FastEthernet1/20

description Trunk to 3400ME GE0/10

no ip address

switchport

switchport trunk encapsulation dot1q

switchport trunk allowed vlan 2109,2116

switchport mode trunk

Again thanks for the input on this issue.

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