Mar 04, 2026
To troubleshoot why a MAC address is not transmitted or learned by the peer device, consider the following steps: Check the Switch''s MAC Address Table: Make sure the switch has
Aug 27, 2025
Usually a host (it can be a PC, IP printer, IP camera, etc) cannot send BPDU''s, the BPDUs are actually the language used by the switches to exchange information to select a root bridge, now if
Apr 06, 2026
The fact that your switch appears to be keeping secrets like MAC addresses could be an issue - but try a few of those other suggestions before you jump to the switch.
Nov 25, 2025
A switch with an empty MAC address table behaves like a hub: the first frame it ever sees gets copied out every port. Seconds later it stops doing that, because it has started learning.
Aug 30, 2025
Once that happens, the switch reporting the loop stops trying to learn the MAC address that it sees as looping. That switch floods the traffic from that device to all ports.
Dec 05, 2025
It looks like the APs are working because ports 1 and 20 show multiple mac addresses which means that either another switch is connected to that port or an AP with wireless clients. Try
May 29, 2026
One access control technique that Cisco provides is called MAC Authentication Bypass (MAB). MAB uses the MAC address of a device to
Sep 01, 2025
Hello all, I''ve got a puzzling issue with a particular mac address not being learned over a trunk on my core switch that is present on the access
Mar 18, 2026
The question is why as desktop is the only host connected to switch, it cant send any frame to any other host as there is none.How did switch learn the mac address? To me it appears as
Nov 25, 2025
Inspect the Switch Port Configuration: Verify that the ports are active and properly configured for MAC address learning. Check the ARP Cache: Confirm that the correct MAC address
Apr 13, 2026
What does it mean when a switch doesn''t learn the MAC address
Dec 07, 2025
Hi All, A dell 240 server is connected on two different switch ports with proper vlan configurations on the switch end. The server vendor claims to have put a static ip address without
Nov 24, 2025
I was curious, we have two switches connected to eachother through an access port and on one of the switches there is an AP. Now the switch that is connected directly to the AP should
Jul 11, 2026
If you ping across a routed interface from one vlan to another, you won''t see the mac address of the device you pinged. Instead you will see the mac address of the gateway ip your packet went through
Jan 18, 2026
I''ve seen something like this with issues with native vlan, either between the core and access or access and device like an ap or polycom or phone with a bad native vlan. Look for those mac''s on the
Sep 28, 2025
Hello, I have a Cisco 3750 switch which is connected to a Juniper Firewall on an access port, the switch can learn mac address from the Firewall. The switch uplink is a Cisco 6504 router.
Jun 21, 2026
Why would the switch not add that MAC address to it''s dynamically learned MAC address table. I checked and MAC address learning is not disabled on the vlans or switches in question. The
Oct 20, 2025
MAC address entries cannot be learned on the device, so Layer 2 forwarding fails. Check that the configurations on the interface are correct. Run the display mac-address command in any
Feb 25, 2026
This document describes a scenario where a Catalyst 9300 access switch was learning an upstream MAC address on a downstream port.
Aug 23, 2025
Contribute to annontopicmodel/unsupervised_topic_modeling development by creating an account on GitHub.
Dec 19, 2025
Ports with the standard 802.1x configuration have no problems connecting to the network and the switch learns the devices mac-address. The only way that I''ve found to get devices on non
Jul 10, 2026
All, I have two switches connected to each other. Switch-A is the core switch which connects to mutliple switches and Switch-B is connected to hosts. On Switch-B, I see an arp entry
Nov 13, 2025
I connected a laptop, and then a fluke tester to a switch interface, but it didn''t learn the MAC address. I understand that the switch will learn MACs from incomming frames, so shouldn''t the switch have
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