Procurve Trunking to Multiple Aggregation Switches

[NPDC]

Hi,

I'm new to the HP Procurve line, and trying to understand a network configuration I've inherited. The HP Procurve access switch has a 2-port static "trunk" configured, with each port connecting to a different Cisco aggregation switch that are interconnected with one another. The Cisco switches are not configured for VSS or other MLAG solution. With this scenario, STP is NOT blocking any of the ports. Is there some feature within the HP trunk that allows this configuration, with both uplinks being active?

Thanks.

[Vince-Whirlwind]

Newer Procurve firmware introduced the capability of "distributed trunking" which gives you what you are seeing.

Not sure what you have to do on the Cisco end as I never used "distributed trunking" with Procurve - Cisco.

[EricAtHP]

Some HP devices do support a feature called Distributed Trunking (DT). DT is useful when you have two HP switches connected to any switch that supports LAGs. I don't think that is the situation we have here.

In my mind, the cisco switches must be doing some kind of stacking or MLAG. I assume the cisco switches are stacked meaning the look like one logical switch to everything connected to them.

[NPDC]

Thanks for the replies. I will look into the distributed trunking feature, but not sure if my HP 2910 supports it.

I can confirm that the Cisco 6500 switches are not stacked and there is no VSS configured. If I view the MAC table on the Cisco switches, the HP switch MAC address always appears on the directly connected interface on one of the 6500 switches. However, the other Cisco switch inconsistently shows the MAC on either the interconnected 6500 link or the directly connected interface to the HP. Seems like it randomly jumps between the two, but not because STP is blocking any port.

[Richard Litchfield]

The 2910 does not support distributed trunking (DT). Only the switches with full ProVision ASICs support Dt (5400, 3800, etc). The 2920 with the "ProVision Lite" ASIC does not support DT either.

It sounds like a misconfiguration. Aggregation of any sort is only supported when both ends can cope with it. Each end must appear as a single entity (ie single switch or stack/cluster/group of switches).