Dynamic mac address

[gowdakssujan]

How do switches learn dynamic mac addresses?

Say S1 is connected to S2(fa0/1-fa0/1)

Where do '0001.630b.3b01  DYNAMIC  Fa0/1' come from...

S1#sh mac add

Mac Address Table

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

Vlan Mac Address Type Ports

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

1 0001.630b.3b01 DYNAMIC Fa0/1

S2#sh spa

VLAN0001

Spanning tree enabled protocol ieee

Root ID Priority 32769

Address 000A.416B.256E

Cost 19

Port 1(FastEthernet0/1)

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Bridge ID Priority 32769 (priority 32768 sys-id-ext 1)

Address 0050.0F34.663C

Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec

Aging Time 20

[luis_cordova]

Hi @gowdakssujan 

I think this guide can help you with your question:

https://www.cisco.com/c/en/us/td/docs/switches/datacenter/nexus5000/sw/configuration/guide/cli/CLIConfigurationGuide/MACAddress.html

Regards

[Jaderson Pessoa]

@gowdakssujan Hello,

Each interface on a switch when have a device plugged switch learn mac address automatically of device connected to this port trough broadcast,  some case when device need request a DHCP address, some time when device need send a packet to a another device/address port learn his mac address information that will be used for CAM or TCAM, look an exemple and the diffrence between them.

CAM and TCAM: https://community.cisco.com/t5/networking-documents/cam-content-addressable-memory-vs-tcam-ternary-content/ta-p/3107938

MAC learn Process: https://learningnetwork.cisco.com/message/143572#143572