Will this cause a broadcast storm/loop?

[ScottDrew]

I have 3 2960g switches that each have about 40 devices (pc's, printers, etc..) attached to them.  Each of these 2960 switches has one port connected to a port on a  "core" switch, which is a 3950g.  The 3950 has 3 switches and all of our servers (12) conected to it's ports.  The network seems to be running alright, however most, if not all, of the port lights on ALL switches blink wildly(at least I consider it "wildly").  Am I doing this wrong?  Is there a better way to connect all these switches?

Also, this configuration is for our first floor.  The second floor has the exact same configuration, and the two 3950's (one upstairs, one downstairs) arec connected via fiber.

Thanks for any help.

[Leo Laohoo]

 if not all, of the port lights on ALL switches blink wildly(at least I consider it "wildly").

It's fine.

Main thing to consider is there is only one uplink per 2960 to the 3750 switch.  if you have more that two, then etherchannel them.

Make sure you have "spanningtree bpduguard enable" on all your ports (excluding the uplink).

[David Hornstein]

Hi Scott,

I think I like yours comments and  leolaohoo reaction .

We don't know your Layer 3 setup, but broadcasts will stay in a broadcast domain. A broadcast will cause activity LEDs to flicker. 

I would expect to see on a regular basis multicast and broadcast  packets that make the activity lights flicker in unison.  A bit daunting at the time, as your rack of switches flashed in unison like a christmas tree but as you said "the network seems to be running all right"

To ease your mind, you could look at a wireshark capture  and see if you can coordinate looking at a activity LED flash  and the wireshark capture to see the types of packets that might be worrying you.

I just did a wireshark capture  on my PC that you can see below.  I captured only  20 packets.  It was interesting that  just about every packet is a broadcast packet that will cause all port LEDs  in my layer 2 switch network to flicker.  But I know my layer 2 network is just fine.

Never hurts to be cautious, and monitor switch MIB variables and wireshark capture to see what is really happening on your network.

One positive thing to do if you are feeling like you would like better monitoring on your network,  and you reside in the USA or Canada  is to look at the new onplus appliance with included service   we are offering  for our partner community.

check out the URL below and  the cost of appliance p/n  ON100-K9

.

http://www.cisco.com/en/US/prod/collateral/netmgtsw/ps5734/ps11792/datasheet_c78-680690.html

regards Dave