Packet capture from a Cisco device and export it to Wireshark
Ran into a situation where I needed to perform a packet capture on the WAN interface of a router that was facing an ISP. The site was rather remote and so putting a hub in between the router and ISP and capturing the packets via Wireshark was going to be very time consuming. Here is how to perform a packet capture right on the router and then export the capture to Wireshark for analysis.
- Create the capture buffer monitor capture buffer holdpackets monitor capture buffer holdpackets size 2048 max-size 1024
- Create capture profile. (This will capture everything on the router, but you can use an access-list to filter this down) monitor capture point ip process-switched capturepackets both
- Associate the profile with the buffer monitor capture point associate capturepackets holdpackets
- Start the capture monitor capture point start capturepackets
- Generate traffic you want to capture and then view the buffer to verify captured packets (optional) show monitor capture buffer all parameters
- Stop the capture monitor capture point stop capturepackets
- Export the capture via TFTP for viewing in Wireshark monitor capture buffer holdpackets export tftp://10.1.1.11/capture.pcap
- Clear the buffer and start the capture over again at step 4 to repeat monitor capture buffer holdpackets clear
Here is the Cisco document that goes into further detail: https://supportforums.cisco.com/docs/DOC-5799