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Community Member

In STP.Port Identifier = ?

Is the port identifier = port priority and MAC address

or

port identifier = port priority and inteface number (Eg: 128.2 here 128 is port priority and 2 is interface numeber such as Fa0/2)

Which is corrrect ? I'm bit confused.

Actually i got this doubt as i was reading the below info on cisco site:

http://www.cisco.com/en/US/docs/switches/lan/catalyst2960/software/release/12.2_53_se/configuration/guide/swstp.html

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Spanning-Tree Topology and BPDUs

The stable, active spanning-tree topology of a switched network is controlled by these elements:

The  unique bridge ID (switch priority and MAC address) associated with each  VLAN on each switch. In a switch stack, all switches use the same  bridge ID for a given spanning-tree instance.

The spanning-tree path cost to the root switch.

The port identifier (port priority and MAC address) associated with each Layer 2 interface.

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Regards,

Chandu

Regards, Chandu
2 REPLIES
Cisco Employee

In STP.Port Identifier = ?

Chandu,

In STP, the Port ID has two parts: configurable priority and a fixed port number (which is not the MAC address). On many switches, the port number is exactly the number after the slash, i.e. Fa0/1 is 128.1, Fa0/24 is 128.24. On some switches having GigE uplinks, Gi0/1 is 128.1, Gi0/2 is 128.2, and Fa0/1 starts with 128.3, Fa0/2 continues with 128.4, etc. The port numbers have no particular meaning except being unique for each port on a switch.

Best regards,

Peter

Community Member

In STP.Port Identifier = ?

Peter, so as per your reply. I think cisco mention the third point worngly.

Regards,

Chandu

Regards, Chandu
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