brige id and multiple stp instances

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Jul 5th, 2008
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hi every body !

I am just wondering if each stp instance on a switch requires unique bride id? Can we use same bridge id for multiple stp intances?

I read if a switch support 1024 mac or more mac addresses, then traditional method is used for bridge id.

does traditional method use differnt bidge id for stp instances running on switch or same?

If different bridge id is used for each stp,are these mac addresses chosen from the pool of mac addresses , the switch has?

If mac addresses are chosen from the pool of mac addresses , then there is possibility two switches might choose the same mac address for the stp instance. what happens in that case ?

thanks alot !


Correct Answer by Jon Marshall about 8 years 8 months ago

Sarah


Each vlan requires a unique bridge id for STP. If the switch supports 1024 mac-addresses then one mac-address per vlan is used to for the bridge id so each vlan has a unique bridge id.


There is no possibility (or at least there shouldn't be) that 2 switches could use the same mac-address because unlike IP addresses mac-addresses are globally unique ie. the same mac-address should never be assigned to more than one device, whether that device be a switch, router, NIC etc.


Jon

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Correct Answer
Jon Marshall Sat, 07/05/2008 - 13:41
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Sarah


Each vlan requires a unique bridge id for STP. If the switch supports 1024 mac-addresses then one mac-address per vlan is used to for the bridge id so each vlan has a unique bridge id.


There is no possibility (or at least there shouldn't be) that 2 switches could use the same mac-address because unlike IP addresses mac-addresses are globally unique ie. the same mac-address should never be assigned to more than one device, whether that device be a switch, router, NIC etc.


Jon

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