2.1.a (i) Managing MAC Address Table

Here are some facts, commands, and information related to 2.1.a (i) Managing MAC Address Table, I will use to build the flash cards for this section. I’m not going to waste your time with explaining the basics of MAC address table population.

You will mainly be utilizing the mac address-table show commands to trouble shoot issues, here are the commands you need to know:

Switch#sh mac address-table ?
address Address to lookup in the table
aging-time MAC address table aging parameters
count Number of MAC addresses in the table
dynamic List dynamic MAC addresses
interface List MAC adresses on a specific interface
multicast List multicast MAC addresses
secure List secure MAC addresses
static List static MAC addresses
vlan List MAC addresses on a specific vlan
| Output modifiers

You should be aware of the default mac address-table aging time of 5 min or 300 sec.

To change this value use:

mac address-table aging-time
and then to verify
show mac address-table aging-time

When reading the table you should know that STATIC entries are MAC addresses for different multicast addresses that the switch or router listens to.

EX: OSPF multicast, or BPDUs , or any other process

These are designated by the ports = CPU

Anything that says dynamic, was dynamically learned via traffic ingress on that interface

It is possible (but very rare) that you may want to disable MAC learning in the CAM able.

conf t
no mac-address-table learning

sh mac address-table learning


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