MAC Address Issue

[jm.virtual01]

I am facing authentication issue on ISE but meanwhile, I have noticed one more issue and I guess because of that, I have an authentication issue on ISE. I have Cisco Catalyst 3850 switch when I hit the sh mac address-table command, it shows me same mac address twice.

    Mac Address Table

-------------------------------------------

Vlan    Mac Address       Type        Ports

----    -----------       --------    -----

377    2c44.fd2f.9471    DYNAMIC     Gix/x/x

377    707c.6901.277a    DYNAMIC    Gix/x/x

256    707c.6901.277a    STATIC      Gix/x/x

Could someone have any idea on this? Why it is showing me the same mac address twice on the interface as a static and dynamic. It is a common phone and pc arrangement on the switch port.

[Damien Miller]

This would lead me to believe that you are using port security, do you want to share your interface config? If you are using port security with dot1x, it has some odd behavior, and the general recommendation is to avoid using both together.

[kthiruve]

See if this post helps you. Difference between static and dynamic MAC.

https://community.cisco.com/t5/switching/mac-address-dynamic-and-static/td-p/1660466

This post belongs to the switching community where you can get answers.

-Krishnan

[brselzer]

Hello,

You are seeing the mac address learned in two different vlans. I assume vlan 377 is your data vlan and vlan 256 is your voice vlan.

It is not uncommon for phones to reach out in the data vlan before they learn what the voice vlan is from the switch. This is probably expected behavior. 

Hope that helps!