spanning tree

[Kekoa]

I am currently using 2 gigabit lasers to connect to a switch across the street. Right now they are running in gigachannel and everything is fine. We just set up a floor in another building on the other side of us so we are going to split the two gigabit lasers and add a 100baseT laser for each building.....soooo it looks like this.


building A is going to have 1 gigabit and 1 100baseT link to building HQ....and building B is going to have the same, 1 gigabit and 1 100baseT link to HQ.

QUESTION:

How can I specify which link SPANNING TREE disables? Obviously I want to use the gigabit link for each connection and have the 100baseT connection as a back up.

 

[Jsteve]

becase the cost of the gigabit channel is higher, STP will automatically use that port and block the 100baseT.

you can manually adjust the port cost with the command:
switch (enable) set spantree portcost 2/1 10

The range is from 1 to 65,535 and the lowest cost will be selected to forward frames.

 

[Kekoa]

Thanks, on the same note, is there a way that I can specify how long it takes for spanning tree to bring up the back up link? The Gigabit might bounce time to time (due to rain/fog/wind/whatever) and I don't really want the 100baseT to come up unless the gigabit is down for a couple of seconds. Is it possible to set the delay for spanning tree?

 

[Jsteve]

You can adjust the maxage timer. The default value is 20 seconds. This is the timer that the switch uses to start convergence when the switch does not recieve a BPDU within a certain amount of time.

You need to do a little research on STP before you start changing timers, you can cause more problems by incorrectly adjusting timers. Please note also that the timers on each switch must be set the same.

 

[Kekoa]

Awesome, thanks! I'll hit the books this week! Thanks for your help!