Tutorials · Switching
How to Use Port Mirroring to Troubleshoot Network Problems
Copy traffic from a port or VLAN to an analyser port and capture it with Wireshark.
Before you start
- A managed switch
- A laptop with Wireshark
- One free switch port
Step by step
Pick the source
Choose the port or VLAN to observe, for example the uplink of a slow access point.
Configure the session
Mirror both directions to the analyser port.
monitor session 1 source interface gigabitEthernet 0/5 both monitor session 1 destination interface gigabitEthernet 0/24
Capture
Connect the laptop to the destination port and start Wireshark on its wired interface.
Remove the session
Mirroring adds load and exposes traffic; delete it when you are done.
no monitor session 1
Commands are generic, industry-standard examples. Exact syntax and menu names vary by model and firmware; check your device's manual on the Documentation page.
Pro tips
- Do not mirror a 10G uplink to a 1G port: packets will be dropped.
- Treat captures as sensitive data and delete them after analysis.
FAQ
Frequently asked questions
Does port mirroring affect network performance?
Usually not noticeably, but heavy mirroring on busy links adds load. Remove sessions after use.
Keep learning
Related guides
Troubleshooting slow Wi-Fi
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Separate staff, guests, voice and cameras into their own VLANs: create VLANs, set access and trunk ports, and verify traffic separation.
Read more →How to Set Up Inter-VLAN Routing on a Layer 3 Switch
Route between VLANs at wire speed using switch virtual interfaces (SVIs), a DHCP relay and ACLs that control which networks can talk.
Read more →How to Configure Link Aggregation (LACP) Between Switches
Bundle two or more links into one logical link for more bandwidth and redundancy using IEEE 802.3ad LACP.
Read more →Stuck on a step?
Ask Navijin technical support or an authorised partner for help with your configuration.