Network goes down when one user starts working

[JeepinEd]

I'm trying to help my friend Pete figure out the following problem:

He is subleasing an office to one person, who is sharing Pete's network . Whenever this person comes in and tries to do his thing, the whole network goes down. Now here are the details...

Pete is using AT&T U-verse, with the standard modem acting as a DHCP server. He has a 24 port switch connected to the modem, which feeds all the computers. There is also a wireless router connected to the modem.

His tenant has a Polycom VOIP phone and a laptop running Windows 10. Both are connecting through a 4 port switch in his office, that runs to the 24 port switch. Everything will be fine, until he logs on to a program called GoldMine. Once he does, it's only a matter of minutes before the whole network crashes.

We have already replaced the 24 port switch and the 4 port switch. I connected his VOIP phone and laptop. I Logged on to GoldMine, started streaming video, and left it there. Everything ran fine for several hours, so I shut his PC down. This morning, when the tenant arrived and logged on, it lasted 15 minutes before the whole network crashed again.

I'm stumped. My guess is that it has something to do with the program he's running, but I'm not sure what to try next. I know the basics of networking, but I'm no expert.

Any suggestions will be appreciated.

 

[razel]

What exactly happens when the "networks goes down." Internet router reboots? Switches reboots? Hogs up bandwidth?

 

[mxnerd]

This https://www.goldmine.com/ ?

If it is, it's just CRM, no way it will cause network shutdown. It must be something else on his computer. Probably torrent download?

 

[JeepinEd]

When the network goes down, everyone loses internet access. I'll ask if peer to peer connections still work.
He's not doing an torrent downloads, as far as I know.

 

[JeepinEd]

..and Yes. That GoldMine.
After they lose internet access, they'll reboot the router & switches, then everything comes back up again.

 

[JackMDS]

Just describing functional occurrence and No real tech data, does not provide any clue to what is wrong in the Setting.

There are two options.

1. if someone is a network savvy let him check all the connection, and study the IPs and Routing assignments.

2. Not so savvy, do elimination.

I.e., disconnect everything from the tenant Router/VoIP arrangement and start to add up the system until it goes down.

 

[JeepinEd]

Just describing functional occurrence and No real tech data, does not provide any clue to what is wrong in the Setting.

There are two options.

1. if someone is a network savvy let him check all the connection, and study the IPs and Routing assignments.

2. Not so savvy, do elimination.

I.e., disconnect everything from the tenant Router/VoIP arrangement and start to add up the system until it goes down.

We basically did #2. It's just a phone, a laptop and a wireless printer. I thought it may be a faulty switch We connected the phone, let it sit for a while, then did the same with the laptop. There were no issues until the tenant showed up the next morning and started working. Fifteen minutes after he began work, everyone lost internet connection.

Right now, I've suggested the tenant bring his home pc into the office to see if there is still an issue.

 

[dave_the_nerd]

Could be his mini-switch. Sometimes those can cause problems if they're overloaded or faulty.

Double if the 4-port "switch" is actually a 4-port router. Take a good look at that.

 

[mxnerd]

Check if his devices have fixed IP addresses that cause IP conflicts.

Some smart switches (like Netgear) also have IP addresses.

 

[mv2devnull]

Double if the 4-port "switch" is actually a 4-port router. Take a good look at that.

Yes. If it is a consumer router and its DHCP is not disabled, then that DHCP will compete with the main DHCP and provide nonsense settings to devices that update their leases.

I've heard that some users have plugged those "routers" to enterprise networks, and eventually received calls from very very provoked IT admins.

 

[JeepinEd]

It's a new linksys 5 port gigabit switch, model SE3005. I'll have to check his pc to see if it has a static IP, although we had it running for hours yesterday with no ill effects. It wasn't until the guy came in this morning and started to work that it crashed the network.

 

[ylin0811]

It sounds like the crash is due to broadcast storms. Use wireshark to analyze the network during business hours and you would easily see if there is a broadcast storm on the network.

 

[JeepinEd]

It sounds like the crash is due to broadcast storms. Use wireshark to analyze the network during business hours and you would easily see if there is a broadcast storm on the network.

I'll give that a shot. I sublease from him as well, so next time I'm in the office I'll give it a shot.