Network Slowness and Intermittant Connectivity Issue

Hello, I have a customer who is experiencing network slowness and intermittant loss of connectivity across the entire network.

The network is 24 bit with 4 Dell 2724 switches daisy chained together.

I wasn't sure if it was possible to mirror a port on these switches so I put a hub inline with their domain controll/file server and ran wireshark.

I didn't see anything along the lines of a broadcast storm or any strange traffic on that port.

90% of the time all pings to devices on the network respond fine, the other times, I can ping some devices and some I cannot. The outages last from just a few seconds to indefinately.

This behavior occurs on multiple ports on "all" of the 4 switches.

I noticed some really odd behavior when I tried running a ping sweep on the network. I had 5 continuous pings running to a handful of hosts on the network, some would reply, some wouldnt. It was random. Now, the strange part,..... "everything" started to reply to pings immediately after I ran the ping sweep (using angry IP) across the entire subnet.

I few moments later, random pings started to not respond again... I ran another ping sweep and everythign immediately began reaplying for a few minutes.

I tried running the pings and ping sweeps from multiple computers on the network and the same exact behaior happeded every time... Pings would drop to random devices until I ran the ping sweep... then all was well for a few minutes.

Any idea as to what could be going on here?
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Most likely a bad switch(s).  Espeically if they are truly daisy chained together, and not in a star topology.

Are this configured switches? are you able see errors?
Their might be packet drop on switch due to collision.
Do you have spanning tree enabled?
Most sw have STP enabled by default, If you had any stp problem, your network will not function.
So focus more on packet drop, Bad cable connecting 2 switchs, Check speed/duplex?
miteldatanetAuthor Commented:
Well I found the issue. The customer had plugged a small D-link home grade switch in a cubible and it basically brought down the entire network.

The odd thing, I could not see anything suspect in wireshark.

I had to resort to interviewing the employees trying to find out what changed on the network. I eventually found this switch.... unplugged it and all was well. I plugged it back in, and pings started dropping all over the place.... removed it, and all was well again...

Thanks for the assistance.

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Network Management

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