cancel
Showing results for 
Search instead for 
Did you mean: 
cancel
316
Views
0
Helpful
2
Replies

Catalyst 3524 - Capturing fragmented packets

rholdsrdh
Level 1
Level 1

Greetings,

I have run into an interesting issue with a trunked connection to my ASA.

Scenario: ASA-5510 connected to a Catalyst 3524 switch via a dot1q trunk. There are approximately 12 vlans configured and passing traffic.

The ASA interface shows no errors; the Catalyst switch is incrementing runts fairly rapidly.

From what I have read this typically is a cabling or hardware issue. We changed ports and cables on the Catalyst switch to rule out that side. Both ASA and Switch are set to Full Duplex/ Speed 100.

From a troubleshooting perspective, I am limited on my packet captures due to the switch and/or my NIC hardware discarding 'bad' packets. I don't have access to a hardware packet capturing device or a NIC with that capability.

To anyone's knowledge, is there a way to capture the packets being dropped at the switch port? I have a port monitor set up and have disabled "checksum offloading" on my NIC; so far that is the best I have come up with.

It looks like the switch will increment the runts counter, but not log any of that info.

I am eliminating any other port issues I see on the switch, but that hasn't made a difference so far.

My apologies for the long post, but I do appreciate your patience and expertise!

Thanks for your time!

2 Replies 2

drolemc
Level 6
Level 6

Use below command to capture fragmented packets.

Switch# Show cdp traffic

This command will displays total no fragmented packets

rholdsrdh
Level 1
Level 1

Thanks for the info - I will be able to use that for future troubleshooting!

I have resolved the incrementing runts issue with an IOS upgrade on the switch (to current level for the Cat 3524).

After the upgrade, the counters no longer increment. I was hoping this would be the case; we were just waiting for a maintenance window to complete the upgrade.

Thanks again!

Getting Started

Find answers to your questions by entering keywords or phrases in the Search bar above. New here? Use these resources to familiarize yourself with the community: