Internet access slows down and stops.

Hi

Have just one Windows 2003 Server, two HP ProCurve 2650 switches stacked, one Zyxel ZyWall 35 Router/Firewall. Category 5 and 5e cables.

When more than 25 domain users go on the Internet, things get very very slow, and sometimes come to a standstill. It can appear as if the ISP has gone down.

Also, need an explanation for this. If the domain server goes down, people can't get out on the Internet. I don't understand why since the gateway should still be locally held until the lease expires, and the gateway is our firewall local IP address, not the servers. Why would this be happening, and I wonder if this problem is related to the one above?

One other thin (that may or may not be important / relevant to my problem) is that on the commander switch, I'm getting repeated errors of excessive CRC alignment errors on port 35, and "too many undersized/giant packets" error also on port 35. Don't know if this is relevant or not.

The main  problem is the loss of Internet connection when several users are on. It's a 2 MB connection we have.
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Jason210Asked:
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MATTHEW_LConnect With a Mentor Commented:
If the DC goes down, internet access appears to fail.  Most likely because DNS is hosted internally on the server.  Without DNS the internet appears down.  When this happens you should still be able to browse web sites by IP address as a test.

Port 35 could be going bad, or most likely a device with a bad NIC is attached.  This is probably not causing your problem.

What type of internet connection do you have?  Is this just web browsing that users are doing, or file transfers etc?  You may want to try to monitor your external bandwidth that is being used.  You can try MRTG if your WAN router supports SNMP to see what type of bandwidth is being used.
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Jason210Author Commented:
Thnx...will look into this asap and get back to you.

So if DNS server stops, Internet is effectively down, bevcause no-one is going to start typing Ip addresses. What would be a way around this? Have a secondary DNS server?
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MATTHEW_LCommented:
You could have a secondary dns server possibly at your ISP.  Just make sure that it is below the internal one, otherwise clients may have problems resolving internal names for services.  It would however help in a failure of your dns server.  

A possibly better solutions is to create an additonal internal dns server (a replica of the current) this way internal and external names can be resolved when the primary fails.
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