Network HA with RSTP

[RobB_8]

I am looking at opinions on how to configure a HP solution for a network core ring. I have 5 switches in the core, 1 6400 and 4 3400's all configured in a ring via 10GB-CX4. The goal is to simply provide HA in the case of a switch/tranceiver failure. I cannot do Meshing as the 6400 is the router. Because there is voip and other packet sensitive apps running thru the core, quick recalculations and quick recovery are a must. I have played with many different RSTP settings with little luck.
Does anyone have a recommendation on a good settings for things like:
-switch priorities
-switch times ie hello time and forward delay
-port values ie cost and priority etc
Thanks

[Marco Wessel]

What are you seeing using the defaults that you aren't content with? I.e., what do you mean by 'little luck'?

[RobB_8]

My problems are due to what appear to be recalculations of the loop. When it does this I drop connections on the core for 1-2 seconds, which is not a problem for most apps, but some connection sensitive apps like the IP phones is a big problem. I would have thought that setting a root and secondary root and put all the rest of the switches with lower priorities would be enough to prevent the recalculations. I guess I am wondering of anyone else has set up a similar ring with VoIP and had no issues with periodic connection drops.

[Marco Wessel]

Well, the recalculations aren't going to get much faster than that. However, they shouldn't be happening: STP is there to keep your network going in case links fail, not to randomly decide things should be different.

What might be causing the behaviour you're seeing is link state changes on edge ports. A link state change is normally a reason for STP to get all giddy and start recalculating things. They also aren't supposed to happen in your network core, so that's fine. They do happen on the edge, however, as machines get rebooted, disconnected, etc. so switches know to not generate topology changes when link states change on edge ports. So to get to it: are all the edge ports on the switches with STP turned on marked as such?

[Pieter 't Hart]

"I cannot do Meshing as the 6400 is the router"

As you depend on the 6400, why not do a star with the 6400 as center instead of a ring?

If redundancy is the main issue, you need a second 6400!