Can switches be causing Slow internet?

[HSTech]

In my network, all the computers are networked with switches, and then access the internet thru a T1 connection. Lately the internet has been so slow its nearly impossible to surf. I've consulted some other people and they seem to think that my switches are 'chattering', they are out of sync or something and are sending way too many packets, and flooding the network. they said that turning the switches off, then turning them back on after a minute or so, will get them back in sync, and hopefully make the internet much faster.

Has anyone heard of this type of thing before? has anyone gotten this to work? Any ideas, suggestions, or comments will be welcome. THanks

 

[jimbopalmer]

I suspect the buzzword you are looking for is broadcast storms, I doubt you have one but you may.

If so, all uses of the network would be slow, files serving, printing, etc. If only the internet is slow you may just have users sharing files, often music, on company equipment, or you may have equipment failure at your end or the ISPs, if it is slow when no one else is online it is most likely configuration or equipment. I tried to remain child-like, all I acheived was childish.

 

[wybnormal]

WHile a broadcast storm is a possiblity, they tend to come and go like the tide so you would see periodic trouble. A more common problem is the switches will be set to auto 10/100 and the NICs on the servers, workstations, routers etc can not autonegotiate with the switches and lock in at a given speed. Older NIC have this problem as so some of the 3com cards. The problem is the switch will keep tearing down the connection since it wont stay locked.

A common and useful tool to help troubleshoot is to use traceroute (for MS it's tracert). This will show you where the slow point is alot of times. Think of it as a ping on steriods. Try it from different locations on the network to a given place. You will start to see a pattern.

MikeS
Find me at

http://www.packetattack.com

"Take advantage of the enemy's unreadiness, make your way by unexpected routes, and attack unguarded spots."
Sun Tzu

 

[HSTech]

Alright lets say first, that i do have a broadcast storm problem. What would i do to fix it? Would turning the switches off, then turning them back on, fix it? (like the advice i got from someone).

Or lets say its not a broadcast storm, but that my switches can't lock in at a given speed. what would i do to fix that?

Any suggestions or help will be appreciated.

 

[wybnormal]

If it's a broadcast storm, you almost need a sniffer to find out who is spewing the broadcast messages. Like I said, most broadcast storms tend to cyclic in nature and normally would not need a hard reset to fix it. They would fix themselves baring a hardware failure like a bad nic.

If it is some ports that can not lock down, a clue would be to go into the switch and pull up the port(interface) stats. You would see alot of CRC errors on the ports that refuse to sync up or you will see alot of input errors. To verify, you would first clear the counters to get a clear slate:
Switch#clear counters
Clear "show interface" counters on all interfaces [confirm]
Switch#

The fix is to lock the ports manually to whatever speed they will support without going into spasms. It might be 10 half, 10 full or even 100 half duplex.

MikeS
Find me at

http://www.packetattack.com

"Take advantage of the enemy's unreadiness, make your way by unexpected routes, and attack unguarded spots."
Sun Tzu