HP ProCurve 2920 switch stack topology for TWO switches? Ring vs. Chain vs. trunk?

Question

I have a customer whose two HP ProCurve 2910al PoE switches have failed. This was backing a VoIP deployment for a small call center. They are interested in replacement PoE switches, but there's a concern about the stack design.

This is primarily voice traffic, with PCs connected inline with phones running at 100Mbps. The replacement switches will be HP ProCurve 2920-48G PoE devices.

There will only be two switches here. There is no plan for growth in port count. The switch ports will be less than 50% utilized.

• For a two-switch setup, does it make sense to stack these switches via the stacking modules (additional $900 per-switch, plus stacking cables)?
• If I do stack, should this be done with a single link between stack members or a dual-cable link topology (shown below)?
• Or, given the cost impact of the stacking modules + interconnects, does it just make more sense to run a trunk between a few Gigabit ports on each device?

Solution 1

To quote yourself, "The stacking cost just isn't worth it at this scale". Yes, you get some better administrative options with stacking, but it's probably not worth it here.

Talking about stacking in general, with just 2 switches, only one stacking cable is necessary. Once you get to 3 switches or more, a ring is best because then any one switch could fail and still provide access to the other switch(es).

Solution 2

Just use a few links between the two switches in a LAG.

1. it'll be cheaper
2. you'll be easily able to increase bandwidth between the two switches by adding a port should that become necessary
3. you can always upgrade to stacking modules later

Comments

[Steve Townsend]

That's about it. Without any specific requirements for things like translate(vendor.PROCURVE, "VPC") stacking the switches isn't necessary.

[ewwhite]

Why do you think they present the ring topology for two switches in their docs? I thought it was a bit odd.

[longneck]

I have no idea. Drove me nuts for a couple of weeks when I kept getting stack failure messages and the guy who installed them had no idea what was wrong.

[Steve Townsend]

Can two cables used for redundancy in this config?

[longneck]

@MikeyB That would be a good reason to have ring set as the default.