Blocking a link on GbE2?

[Anders_35]

Because of maintenance work, I wanted to reroute traffic from one network link to another. Specifically, I wanted traffic from a blade enclosure to exit through Switch B (right side) instead of Switch A (left side).

A and B are configured identically, they run RSTP, and they both have a 4-port trunk to ProCurve 3424's. Spanning-tree blocks the interconnect trunk (Trunk 1), so both switches keep their uplink trunk open.

Now, I want to block the uplink from Switch A, so that RSTP will open the interconnect links and pass all traffic from A through B.

So, I tried disabling the trunk. (Not the ports, just the trunk.)

Our spanning tree reacted immediately, and a topology change was logged.
BUT Switch A still kept the interconnect trunk blocked, and tried sending the traffic over the now disabled uplink.

So, did I screw up? Or was this as wrong as it looks to me?

[Matt Hobbs]

Hi Anders,

I'm not that familiar with the GbE2's.... instead of disabling the trunk on the GbE2, why not disable those ports on the 3424 instead?

Matt

[Lei.Ma]

and,if 3424 use static trunk. maybe can you try use lacp trunking?

[Anders_35]

Sure, I could've done all that.
But as it happened, I tried to block the link from the blade-end, and I just wonder why it failed.

The only reason we're not using LACP is that originally, the blades were plugged into a switch that didn't support it. (And I'm not sure that the old GbE2 firmware did either.) We just haven't taken the time to reconfigure.

Ray: do you think that this would have made a difference?

[Matt Hobbs]

When you disabled the trunk, did the ports go offline on the ProCurve and remain offline?

I'm imagining a situation where disabling the trunk simply removes it and they become 4 independant ports again, therefore 3 of them would be blocked but 1 would still be active which is why the interconnect trunk was still blocking.

I can't imagine the type of trunk (LACP or other) making any difference on this whatsoever.

[Anders_35]

No, they didn't. That's one of the things that's puzzling.. All 4 uplink ports were forwarding, and the 2 interconnect ports were still blocking.

I am guessing that there is an issue with the way these switches separate ports and trunks. Much neater on the procurves, where for all practical purposes, the trunk replaces its ports.

[Anders_35]

Just to clarify:

>All 4 uplink ports were forwarding,

RSTP was /listing/ them as forwarding.
But since the trunk was disabled, no traffice made it through.

And the consequence was that there was no link out of that switch whatsoever.

[Matt Hobbs]

Did you check on the ProCurve as well if those ports were forwarding? (Or the GbE2 if you were referring to the ProCurve's spanning-tree forwarding status).

You'll only see the blocking on one side of the link, not on both. I apologise if you knew that.

Anyway, it's sounds very much like that's what happened, the trunk was removed from the configuration, they become normal ports and spanning-tree on the ProCurve blocked 3 out of 4 ports (which is good) and on the GbE2 it looked as though nothing had changed.

[Anders_35]

Yeah, that does sound like plausible explanation. However, there is no trace of STP blocking anything in the ProCurve log.

I've logged this with HP support, so let's see what they say. They did confirm that they have seen issues with the GbE2's confusing a trunk and it's individual ports before.

[Lei.Ma]

sorry about last time reply, but LACP can do Dynamic trunk,when you disable the Trunk maybe the lacp dynamic generate lacp trunk from 4 uplink . and the spanning-tree priority sitll high?
show interface config, show lacp ,show trunks; show spanningtree , after you disable the trunk. check the cost and priority.
i am not sure it,just assumed.