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STP question from access to trunk

Hi,

I'd like to ask you a simple query about PVSTP....

We have a switch called CATS running PVSTP. These ports (G3/0/13 and G4/0/13) connect the CATS with one of our cabins called KONOM HP Blades. Specifically, these two ports respectively connected Cisco Blade Switches that are integrated within the cabin KONOM.

Currently  in the cabin KONOM only have teams working in VLAN 28 (servers ) for that the ports in the CISCO BLADE Switches are like access, but  in the future we will need to have access to other VLANs (eg DMZ , ... ) for  that reason we are evaluating the possibility to change these ports to TRUNKS

For this reason I would like to make you 3 questions :

1. - Is it possible to change the ports 3/0/13 and 4/0/13 CATS ACCESS mode to TRUNK mode in the future?

2 . - What implications would have this change from access to trunk mode in STP ?

3 . - At the time of the change would have affected service ( ports fall and raise again ) ?

Thanks a lot.

1 REPLY

Re: STP question from access to trunk

Hola 

For this reason I would like to make you 3 questions :

1. - Is it possible to change the ports 3/0/13 and 4/0/13 CATS ACCESS mode to TRUNK mode in the future?

- Configuration wise, you can switch between access and trunk or from trunk to access as you wish.

2 . - What implications would have this change from access to trunk mode in STP ?

- Once you configure the interface in trunk mode, STP will reconverge to define the new layer 2 topology, this is due to trunk can carry traffic from simultaneos vlans at the same time.

See in the link below what happens when you add a new link to the layer 2 topology, and the reconvergen process.

http://www.cisco.com/en/US/tech/tk389/tk621/technologies_white_paper09186a0080094cfa.shtml#converge

3 . - At the time of the change would have affected service ( ports fall and raise again ) ?

- Once STP reconvergence, if you run Per-vlan STP, the modifed interfaces will go down and go through the STP process of blocking, listening, learning and finally forwarding (45 seconds or so)

Regards.

Wilson B.

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