MAC Address learning process

Question

Does a switch learns hosts mac address in these following scenarios:

Switch port configured as access and frames received tagged on different VLAN
Switch port configured as trunk and frames received tagged on non authorized trunk VLAN
Switch port configured as trunk without native VLAN and frames received not tagged
Switch port not configured (default), and frames received

And more global question, are these generals rules or does it depends of the vendors ?

Ron Trunk · Accepted Answer · 2019-02-28 14:45:47Z

10

It depends on the manufacturer. For Cisco switches:

Switch port configured as access and frames received tagged on different VLAN

Frame is dropped

Switch port configured as trunk and frames received tagged on non authorized trunk VLAN

Frame is dropped

Switch port configured as trunk without native VLAN and frames received not tagged

Frame is dropped

Switch port not configured (default), and frames received

The default configuration is access port on VLAN 1, so frame will be accepted and the switch will learn the MAC address.

answered Feb 28, 2019 at 14:45

Ron Trunk

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Thanks. You confirm there are systematically no mac address learning in case of frames dropping ?
– bdes31
Commented Feb 28, 2019 at 14:59
@bdes31 When ingress frames are dropped due to an unauthorized VLAN ID, no MAC address is learned from them. Since the port isn't part of the VLAN anyway it wouldn't make sense to learn the MAC but not forward frames there.
– Zac67 ♦
Commented Feb 28, 2019 at 15:35

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