Switch activity lights flickering constantly

Yaayuh! · 16 Nov 2011 at 08:51

Hi all, got an issue here. I think something may be constantly broadcasting or something.
Here's how it is.

All servers have "teamed" connections for load balancing and failsafe. One connection goes to one switch in the server room and the other to another switch.
Both of these switches are also hooked up to the main 3Com stacked set of switches where all the users and the router (and netgate firewall that i've missed out of the diagram) are plugged in.

The thing is, i've not really noticed any network slow down at all, but the 2 switches with the server have the active connection activity lights flickering constantly, in previous experience this is bad. I'm thinking that maybe i've created a loop? or something (a server) is broadcasting constantly.
That said, the 3Com stacked switches' connections do not flicker constantly, just the 2 up with the servers.
It could just be the way that the teaming works i suppose, will look into that side of it.

Any ideas or thoughts appreciated.

ci_newman · 16 Nov 2011 at 09:27

Just turn on spanning tree and figure out what stops working

ots3go · 16 Nov 2011 at 09:43

Has the server farm got its own dedicated VLAN?

paradigm · 16 Nov 2011 at 09:58

Why do you have the router connected to your workstation/end-point switching as opposed to core? No firewall/gateway/edge server?

Yaayuh! · 16 Nov 2011 at 11:00

ots3go said:
Has the server farm got its own dedicated VLAN?

Nope

paradigm said:
Why do you have the router connected to your workstation/end-point switching as opposed to core? No firewall/gateway/edge server?

Sorry, as i said i missed out the netgate firewall that sits in between the router and the main switch stack.

That side of it looks like this:
Internet --> Router --> Netgate Firewall --> Main switch stack

However, that part of network isn't the problem, so lets forget about that.

I think i have pinned it down to the the way the servers NICs loadbalance and failsafe work, they seem to broadcast/multicast frequently.

ots3go · 16 Nov 2011 at 11:26

Would I be safe in assuming all this kit is on the same broadcast domain?

Yaayuh! · 16 Nov 2011 at 12:45

ots3go said:
Would I be safe in assuming all this kit is on the same broadcast domain?

Yes

WILD9 · 17 Nov 2011 at 14:59

Have you tried wireshark yet, I find it quite helpful in identifying odd traffic, broadcast storms stand out like a sore thumb.

Skidilliplop · 17 Nov 2011 at 17:00

Are you experiencing any performance deficit? Some switches the lights do flicker a lot (my Dlinks flash lots more than my Extremes, I'm guessing a flash every 100th framve vs every 500th or something ), but if you had a switching loop believe you me you'd know about it.

As said above: to be safe turn on Spanning tree, which should be never not be enabled on the user access switches at the very least! It's just good practice.

Though from what you've drawn nothing is making any loops and should be fine. Unless of course someone has plugged something in somewhere they shouldn't have. But I don't think they have as a full blown switching loop would completely grind your network to a halt and you'd be fairly sure you had one

If you really want to see what's going on turn on port mirroring on one of the switches and then get a traffic analyzer of some kind on that port. Then you can see what the traffic is.

jimjamuk · 19 Nov 2011 at 11:01

if you had a switching (Spanning Tree) loop your switches would crash and burn - and you would get no response from them and your network would stop

Sounds like heartbeat and background broadcast/multicast chit chat especially if they are MS servers.

Nothing out of the ordinary I think