I want to build a new 'core' for our network. We currently have a 3com 4060 switch acting as the core, connecting all the other TOR and access switches together.

The goal is to add resilience into the core, without compromising performance.

Each switch currently connects to the core with between 2 and 4 physical links configured as LACP trunks.

I am looking at replacing the 3com with a pair of HP 2920 switches with the optional stacking module. My understanding is that with the stacking module, the 2 switches will act as 1 'virtual' switch so I can connect each link from the access switches to each 2920:

Switch Connectivity

The actual question

I know this isn't an unusual arrangement, but my questions are:

  1. Can it be done with the HP 2920 switches?
  2. Should I be using the HP "Trunk" type of trunk instead of LACP?

I've found a lot of conflicting information. A lot of sources say that either Distributed Trunks can only be done with 3xxx or higher switches but the HP QuickSpecs say that DT is possible with the 2920. Other sources say that DT can only be done between a pair of switches and a server (not other switches) but if the DT appears as a LACP trunk to the 'downstream' device then how does it matter?

I could do this using STP to block the links between the access switches and the second core switch, but I don't want to waste all that bandwidth.

1 Answer 1


Distributed Trunking was a means on the ProVision family of HP Switches (35xx/54xx/62xx/66xx/82xx.. not 38xx) to be seen as one switch. It was still two configurations, and there are some features that get disabled on the ProVision switches if enabled. When Distributed Trunking first came out, it was Server to Switch. Its since been improved from switch to switch.

HP now does proper stacking in the ProVision range with the 38xx series, and the 2920 series. It requires a stacking module and stacking cables. but the switches are now seen as one device. One IP Address. One Virtual MAC address. Single Configuration file. Supports Distributed Link Aggregation.

(BTW, I work for Hewlett Packards Networking division in a technical role)

  • 1
    This question is perfectly on topic here!
    – Dan
    Sep 6, 2013 at 12:57
  • Awesome. I got similar confirmation from the HP Networking forums... So now I just need to get the boss to approve the $$$! Thank-you very much for your answer :)
    – fukawi2
    Sep 8, 2013 at 11:22
  • You might also want to try networkengineering.stackexchange.com - quite a few smart networking folks hang out there.
    – Paul Gear
    Nov 5, 2013 at 22:29

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