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Beginner

Why I was taught that MAC Address is fixed?

I was taught that the MAC Address is physical and cannot be changed. But, it seems like MAC Address can be changed for different uses. For example, b0 in the first octet is 0 for unicast purpose and 1 for multi/broadcast purpose. MAC Address can be changed according to needs right? 

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VIP Expert

Re: Why I was taught that MAC Address is fixed?

"I was taught that the MAC Address is physical and cannot be changed."

Not correct. There is a globally unique MAC assigned to every NIC interface, but it can often be overridden for a NIC (see LAA) and there are unicast, multicast and broadcast MACs. The latter two MAC type are assigned/used by need.

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3 REPLIES 3
Enthusiast

Re: Why I was taught that MAC Address is fixed?

Hi,

MAC address in the source field of ethernet frame cant be changed, and what you talk about returns to Dr.Stephan Deering story back to 1990s.

VIP Advisor

Re: Why I was taught that MAC Address is fixed?

Hi

A MAC address is unique around the world but in some situations you could require change it, for example you can change the MAC address associated to the Ethernet interface, for example:

 

interface fa0/0

mac-address xxxx.xxxx.xxxx

 

Hope it is useful

:-)

 

VIP Expert

Re: Why I was taught that MAC Address is fixed?

"I was taught that the MAC Address is physical and cannot be changed."

Not correct. There is a globally unique MAC assigned to every NIC interface, but it can often be overridden for a NIC (see LAA) and there are unicast, multicast and broadcast MACs. The latter two MAC type are assigned/used by need.

View solution in original post

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