RSTP with 2650: getting the root port to work

[jose_104]

Hi,

I just bought some HP 2650's and upgraded the firmware to H.07.32. In my RSTP test environment, I'm trying to get the a trunk to become the root port. However, when I add a 100 Mb UTP redundent link, that new link becomes the root port on the switch. I've set the trunk to a lower cost and a higher priority but, the same thing happens. The trunk gets blocked by RSTP. LACP is disabled.

Can anyone shed some light on this? I've attached a sample image of the topology.

Thanks,

-j

[Stuart Teo]

It looks like the top-most switch is the root switch. RSTP did the right thing by choosing the single 100mbps link as the root port rather than the trunk then.

I'm not sure if you can lower the cost of the middle-left switch to top-most switch path cost to cause the trunk to be selected.

Can you upload another diagram but label the switch and the links this time so that it's easier for me to describe what I mean? :)

[Stuart Teo]

Hi,

I ran an experiment and by adjusting the port priority and port cost, I managed change the root port. My setup is similar to yours. What I did was to to set the trunk to have a port cost of 10 and a port priority of 1.

Remember that root path cost is a summation of all the costs of all the paths on the way to the root switch.

Lower priority numbers = higher priority.

[Stuart Teo]

My fellow car pooler yanked me off the PC yesterday before I could finish my post.

So... as I was trying to say, the port priority is the one that will do the trick. By lowering the priority number (hence increasing the priority), the trunk would become your root port.