3com 4200 24 port baseline switch failing, or needing reset

Posted on 2013-12-02
Last Modified: 2014-05-12
This is way out of my league, so please don't get hyper, if I say something really stupid.  I inherited this old system with a PoE and the switch listed.  The very old 3Com Phone system uses the PoE switch.  Provider swears we have a good connection, computers say that they are connected to internet, yet connections freeze and people are getting bounced out of the sites they are logged into.

If I unplug the switch, it works for awhile and then issues start again.

I don't have one computer here with a serial port on the back.  I might have a laptop at home that might, but am not sure that even with the right serial cable that I would have the knowledge to use the console.

The brains of the phone system used to be hundreds of miles away at our provider's network center.  They could from there see that we had a "storm?" in our switches and reset them.  So there has to be a way as the only connection they had was through the front panel at that time.

I have since brought the brains of the 3 com phone system back to our office and it sits in our rack.

How can I figure out what is going on in these switches.  It doesn't matter if I plug the computers into either switch, they have the same issues.

Thanks a head of time for you help!

Question by:pat8635
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Author Comment

ID: 39693054
I found the 3com device manager that should allow me to look at switch.  It however is not seeing the switch and the computer I am using is plugged directly into the switch.  Any ideas?
LVL 17

Expert Comment

ID: 39849430
A "storm" typically means that packets are going around in a ring among your switches - that could be the case if you have more than one switch, and redundant connections among these switches. In such a case the switches needs to have "spanning tree protocol" running so that automatically some ports are shut down - so the storm stops.

Another reason for a storm is if some user have a small desktop switch, and they have managed to connect two ports to the 3com switch.

One more reason for a storm is if there is a failure of a NIC (ethernet card) of any PC (or if a cable is slightly faulty that makes the NIC go up and down all the time). This storm can usually be fixed by finding which user PC/phone has this problem, and disconnect only that user. You can try fixing it by disconnecting one user at a time until the problem stops. Another way to find it is to have management access to the switch, and check interface statistics - the user with a problem will have a lot of broadcast packets on his port.

If you are considering buying another switch, you need to look at two things for compatibility with the phones. A brand new phone and a brand new switch will interoperate between vendors without any problem - but older phones may not.
    One is the POE version - some very old phones even had power from different copper pins than what is the standard now.
   Another issue is if you use different VLAN for voice and data traffic (in case PC is connected to the phones. These VLANs are automatically configured using the LLDP protocol - in standards - but older phones may not be following standards.

A good switch is the POE version of the Juniper EX2200.
LVL 17

Expert Comment

ID: 39849435
PS. Good switches also have "storm control" that is configurable. For example, it can be set to allow maximum 20% of traffic to be "broadcast" so that this traffic will not affect other traffic.
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LVL 28

Expert Comment

ID: 39849845
When did the issue start? And how are your switches wired? If you have a cable going from one switch to the other, make sure that it is *exactly* one.

Are your phones and computers connected to each other? That might be another thing to look at.

Do you have a decent number of computers that are going on and off the network? If it is consistently the same computers, it is possible that some machines are having issues with negotiating network speed. Check a few of those machines, and you could try setting their network cards to 100 Mbps full duplex (note: you will also need to configure the switch port to which that computer is connected to lock on the exact same speed).

Author Comment

ID: 39850100
I have taken switch out of rack.  Rarely do we plug computers into phones...and again can't get into switch
LVL 30

Expert Comment

ID: 39850625
3 Com has a life time warranty and hot cross ship policy.

Call them for tech support or a replacement.

Expert Comment

ID: 39851070
3Com's lifetime warranty is 5 years after they determine "end of life".  HP bought 3Com.

By default the 4200 series switch tries to obtain an IP through DHCP or a BootP server on the network.  If neither is found it configures the default IP address
If you have the switch out of the network you will need to configure a PC to an address in that network first before you can see it.

Try plugging in one phone at a time to see if one device may be bringing it down.
Above was also suggested that there may be a loop bringing down the network...2 ports on the switch plugged into each other.

Switches do eventually die.
LVL 30

Expert Comment

ID: 39851182
you could try the serial port on the back too.
Just hook up a cable and do a terminal login.

Don't know about hp tech support for 3com,but 3com was great when I had issues with a flaky switch.

Accepted Solution

pat8635 earned 0 total points
ID: 39906864
NOw to find an old serial cable!
LVL 17

Expert Comment

ID: 40049508
And you did not find that the help you received here was worth allocating points to the experts?

Author Closing Comment

ID: 40058434
Took awhile to get a serial cable that was pinned right.  WHy I had so many, no clue.   But was able to figure out what what going one and things are all back to normal now.  Thanks
LVL 30

Expert Comment

ID: 40059161
So I suggested the serial terminal login method and you accept your answer as the correct one?

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