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?
miteldatanetAsked:
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ThaVWManCommented:
Most likely a bad switch(s).  Espeically if they are truly daisy chained together, and not in a star topology.
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bsohn417Commented:
Hey,

Are this configured switches? are you able see errors?
Their might be packet drop on switch due to collision.
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Johneil1Commented:
Do you have spanning tree enabled?
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bsohn417Commented:
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?
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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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