07-01-2025 09:35 AM
I am having issue with one of my desktops connected to my switch interface flipping between two MAC addresses (see the attached picture below for log). When I disconnect the desktop the IP and the MAC issues will not show in the log. I reimaged the desktop and plugged it back in but the issue reoccurred. Please can anyone assist with a solution?
07-01-2025 09:49 AM
- @SamsonOjo What type/model of desktop is this , and what OS are you using ?
M.
07-01-2025 11:49 AM
Switch Model: WS-C3850-24XU. Cisco IOS Software, IOS-XE Software, Catalyst L3 Switch Software (CAT3K_CAA-UNIV ERSALK9-M), Version 03.07.05E RELEASE SOFTWARE (fc1)
Desktop: Dell desktop, Windows 10 OS
07-01-2025 11:55 AM
- @SamsonOjo I suspect an internal issue related to network settings and interaction with Windows 10 on this hardware,
verify adapters, the ip assignment , and stuff like that.
M.
07-01-2025 12:10 PM
Ok thanks.
Just FYI, the two MAC addresses are showing on same port te0/0 (from show Mac-address-table)
07-01-2025 12:18 PM
I reimaged the desktop and reassigned a different IP in the subnet to it, but the issue still persists. Maybe I should just replace the desktop.
07-01-2025 12:31 PM
- @SamsonOjo You could also try to find out, which adapters have those mac address(es) seen in the ARP messages,
M.
07-01-2025 12:03 PM
- @SamsonOjo - For instance , if you see an adapter that is not being used, disable it and check if the problem persists,
M.
07-01-2025 09:51 AM
what is the outcome if you use that mac address and show mac tables | in MAC (is this come from same port ?) - both the MAC.
what device is this ? make be check it got any VM using same IP address ? what IP address MAC resolving to ?
provide more information switch and port config, also end device connected ?
07-01-2025 09:53 AM
There is other device use same IP
Use different IP and check if you see any more error log
MHM
07-01-2025 10:21 AM
I used different IP, the same issue occurs.
07-01-2025 10:24 AM
For check' use random IP like 2.2.2.2 and check
MHM
07-01-2025 11:41 AM
Its a production switch, the port has been configured with VLAN, I dont want to change it. However, I have assigned three different IPs in the subnet to the desktop connected to the switch port, the same issue happens.
07-01-2025 11:50 AM
Show mac address table <both mac>
See if SW learn it from same port
If it learn from same then it issue of PC if different then it IP conflict
Also do
Ipconfig
In PC to check which mac it use
MHM
07-01-2025 12:00 PM
It learns it from the port (see below):
Switch#sh mac-address-table
Codes: *N - VLT Peer Synced MAC
*I - Internal MAC Address used for Inter Process Communication
103 a0:36:9f:4c:3b:54 Dynamic Te 0/0 Active
103 a0:36:9f:4c:3b:56 Dynamic Te 0/0 Active
Also, ipconfig on the desktop shows MAC a0:36:9f:4c:3b:56 and that's the MAC that the PC is using.
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