Procurver 2524's & STP

[Paul Crisp]

Ok, i have 12x 2524's and 1x 2512.

The idea is that we will have stacking kits between each of the switches and then we wanted to close the loop from switch 12 to switch 1 and turn on STP.

Turned on STP lastnight and nothing happened untoward on the network. Came in this morning and closed the loop by adding a fibre connection from Switch 12 Port 26 to Switch 1 Port 25 and suddenly the network goes absolutely crazy !

Done some ping tests and was getting intermittant responses. Also monitored using Procurve Manager + and it was reporting Excessive Broadcasts and Overbandwidth messages.

Eventually decided to tun STP off and remove the loop.

Can anyone give me any ideas why this happened and what else i can do ?

I can supply config info on request

Thanks in advance

Paul

[Kell van Daal · Accepted solution]

How you describe it, it seems STP wasn't working, and thus a loop was present.
When there's a loop in a network, every broadcast will stay on the network untill the the loop is dissolved.
Hence the messages about Excessive Broadcasts.

Are you sure you have configured STP on each switch?
To check that, do a:
show spanning-tree
on each switch, and check if STP is enabled. Also check if the Root MAC Address on each switch is the same.
Also very important is to check if the protocol version is the same on each switch (STP or RSTP).

[Paul Crisp]

Thank you Kell for responding to my request. I will double check that STP is enabled on all of my switches but I don't believe we had a problem there.

With regards to the versions, we are running RSTP on all the switches, i haven't changed to STP to see if this cured any problems.

How do i go about viewing the root MAC address please ?

[Kell van Daal]

To check the root mac address do a: Show span
It's in the first page.
Then if you know who is the rootbridge (and it is the same on all switches), make a drawing with all the switches, and determine which link(s) should be blocked. Working from there should isolate the problem faster.

[seymour999]

Paul:

Which firmware version are you running?

Check the release notes, but I think F_05_17 has a bug that creates large numbers of topology change notifications. Each one causes all switches between the offender and root to flush its MAC address cache.

Have also seen 2524s running this release and set to STP suddenly revert to RSTP after power-cycling.

Finally, if you haven't done so already you may want to reduce the priority of the switch you intend to be root to insure it remains root.

If the priority in all switches is the default, root election will be determined only by MAC address. That will allow a network device with a lower OUI to take charge - probably not what you want. Especially if it's some low-powered device out near the edge of the network.

Hope this helps,
Evan

[seymour999]

> closed the loop by adding a fibre
> connection from Switch 12 Port 26 to
> Switch 1 Port 25 and suddenly the network
> goes absolutely crazy

After you connected the patch cable, did you see a link light on both ports? With only half a link working, STP gets very confused.

[Paul Crisp]

Hi guys,

All problems sorted after a bit of reading and searching the internet.

Basically because of previous network problems without STP enabled i disabled LACP on all ports. It turns out if you enable LACP on the interlinking ports and also disable spanning-tree edge ports to the linking ports as well.

I then went through one by one switch and enabled STP and analysed the affects it was having on the network. Eventually got to the last switch and enabled STP and plugged in the cable to create the loop and everthing worked no problem.

I have successfully pulled the cable as well to test redundancy and this worked and interestingly when i plugged back in the network stopped for around 15-20 seconds and then come back alive, presumingly the STP was re-learning to loop.

Thanks to all for the help on this, below is the config that i'm using just to clear things up

[seymour999]

Paul:

From the config you posted, I believe your switch is running RSTP rather than STP. For STP, on the uplink ports I think the equivalent to "edge-port" is "mode norm".

Cheers,
Evan