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Beginner

Unique mac address on all L2 switchport interfaces

Hi All,

I was wondering why do L2 swicthes have a unique mac address on all switchports ? These addresses are not used for mac rewrite during L2 forwarding since these switches themselves are layer to transit switches. What are these mac addreses used for then ?

Thanks in advance

Regards

Umesh Shetty         

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2 ACCEPTED SOLUTIONS

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VIP Expert

Unique mac address on all L2 switchport interfaces

Hi,

Have a look at this post for some of the answers:

https://learningnetwork.cisco.com/thread/28988

HTH

Under traditional 802.1D, a

Under traditional 802.1D, a different mac address is used for every Spanning Tree Bridge ID (one Bridge ID is required per vlan.

Applicable to PVST+.

 

If you use Extended System ID to define the Bridge ID, then you don't need as many mac addresses because the vlan id will be used as the 12 bits in the Extended System ID, to make it unique from other Bridge IDs 

2 REPLIES 2
VIP Expert

Unique mac address on all L2 switchport interfaces

Hi,

Have a look at this post for some of the answers:

https://learningnetwork.cisco.com/thread/28988

HTH

Under traditional 802.1D, a

Under traditional 802.1D, a different mac address is used for every Spanning Tree Bridge ID (one Bridge ID is required per vlan.

Applicable to PVST+.

 

If you use Extended System ID to define the Bridge ID, then you don't need as many mac addresses because the vlan id will be used as the 12 bits in the Extended System ID, to make it unique from other Bridge IDs 

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