Switch problem? Can ping but cant surf...usually

[DavidMLevine]

I've been going round and round with this problem. I have a 3com superstack 3 3300XM switch connected to a DSL router/modem and to several workstations. If I connect a workstation to the DSL its super fast... works great. If I connect through the hub then usually I cant browse the web. I can PING the web ... ie PING

http://www.google.com

or PING 4.2.2.1 and get good response. Sometimes I can browse, so it seems a performance issue. I set the switch to have an IP and subnet within the confines of my network scheme and set the ports at 100/full. COVAD wont help.. they say it works perfectly. 3Com wont help.. they want to sell me a contract. Microsoft..well you know. Any ideas? I am also running spy-bot and AVG antivirus. It doesnt seem to be clogged (the activity lights would be going nuts if I was spamming myself out of commission)

 

[robertjo24]

#1 Check to see what the interfaces are doing. You say you set the ports to 100/full, but are you getting duplex issues from the DSL router? May need to check the port settings on the router. Are all the ports forced to 100/full, including to your workstations? I would force the port to the router, and allow the workstations to autosense and see how that works.
#2 Try removing all filtering on the switch, or temporarily try an unmanaged switch. If you had a small Linksys or Netgear 5 port switch lying around, (never a bad idea), you could attach a few workstations to see if there are performance issues then.
#3 If the switch has SNMP built in, look at the port stats to see if you have a heavy user on the line eating up your available bandwidth.
#4 Ping between machines with various paket sizes, and try to FTP some large files around your LAN to see if there may be a LAN issue, or if it is jut the WAN interface.

 

[Encryptk33p3r]

What's the firmware rev.?
Have you been out to 3com to find a code upgrade?
What type of DSL router is it?

 

[Encryptk33p3r]

You need to check the MTU size on the DSL, you may need to adjust this. PPOE has a lower MTU, ethernet is default 1500 MTU.
Hope this helps.

Mike Smith
Net-Consul-Team, LLC

 

[RudyL54]

Do you have a firewall in between? You need a crossover cable when you connect your DSL to a firewall. The Firewall connection to a switch is just an ordinary ethernet cable.

You said that connecting the DSL cable directly to a workstation, it worked fine. But after connecting to a hub, nothing came out. It must be the hub. Get something better like a netgear switch with several ports on it. It is auto-sense, so you need not configure it for duplex, 100 bps, etc. The hub must be a old unit that doesn't have an autosense feature.

The hub or switch should act as a transparent device. If it works without a hub, then it should work with the hub, unless you have problem with the hub or cables.

 

[RudyL54]

Another, if can ping but cannot surf, then it could be a problem on your DNS.

DNS resolves the Ip address into domain name.

If you have a firewall, do you have NAT included? NAT translates the local IP to an IP outside the network.

We need to know more info to diagnose where the problem is.

 

[DavidMLevine]

I think I have the problem figured out (more or less) It seems that one of the ethernet cables was crimped in the ceiling at one point or another. I did some troubleshooting by taking all the connections out and reconnecting them one by one. Once I repulled the one bad cable, everything worked fine! Im still not sure if the cable was shorted or wrapped around electrical or what, but it seems it was a physical problem. Very strage but true.

I guess I overthought the problem a little more than necessary.

Thanks,
David