Troubleshooting Connectivity on a Windows Network

Posted on 2005-02-26
Medium Priority
Last Modified: 2013-11-30
Okay, I just need you guys to tell give me suggestions on where to start.  Here is what I got.

A Dell Server with 2 NICs.  One is 100 mbs the other is 1000 mbs.  Running SBS 2003 std edition.

4 Dell client computers with XP pro. (Only 2 are connected as of now)

1 Netgear FS108 switch.

1 Cable Modem

The cable modem is hooked into the 100 mbs NIC on the Server.  The 1000mbs NIC goes to the switch.  All the Client computer go to the switch.

I have no connectivity whatsoever.  The Server's 1000mbs NIC has an IP of  It is also the DHCP server and I cannot remember what the scope is.  But, I did not touch it just left it default(which should work, cause SBS is setup for ppl like me with not so much experience.)

I have not gone through and messed around with anything.  Consider everything a clean install.  I have added 2 users and 2 computers.  The clients are set to obtain an IP automatically.  THe clients will not obtain an address however.

The server has an Internet connection on the 100mbs NIC and it works perfectly.

I cannot ping from the 2 clients that are connected.  I set the clients as a static IP and tried to ping each other with no luck.  

For another test(I don't know if this would work anyway) I connected the cable modem to the switch and 1 client and tried to obtain an IP address.  This also did not work.

Okay, so I think my problem lies in the switch.  I tried different cables.  All the cable I made myself and tested.

While I was trying these different tests I never reset any device, is this a problem?

So, I need suggestions to troubleshoot this.  I don't think it is a physical layer problem, but it's still very possible.  I will be going back tommorrow.  The suggestion that gets me in the right direction or hits it on the head gets the points.

Question by:turtletimer
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LVL 16

Expert Comment

ID: 13412190
OK, lets simplify your life here.   Cable Modem to switch, all workstations and Server to Switch via the 1000 connection. Leave the 100 unplugged or disable it in Network Neighborhood.  Go into your cable modem and turn off it's DHCP.  Give the Internal interface a Gateway address of  It should hold the IP address given out by your ISP on it's external interface along with it's gateway and DNS entries.

Give your server a Static IP address of  Default Gateway will be and DNS will ONLY point to the DNS server, itself,  Now, go into DHCP on the SBS server and look at your scope.  If need be, modify it to start handing out addresses, say at - 254.  In the DHCP options, put the Gateway as and DNS will ONLY be, the IP of your server.  Make  sure the scope is active.  If you run WINS on the server, set that up too amd make sure the WINS option also points to the server.

At the workstations, give them an ipconfig /release, then an ipconfig /renew to make all the settings take.  Now, you should be seeing green lights on your switch from all the machines.  Now, all the workstations should be able to see the Server.  They should be able to join the domain, connect to shares, etc.,  

Then try the Internet.  They all should work properly.  

If you suspect a switch or the ports, get 1 connection working.   You could check your cables on that existing connection that works right now.  Verify all cables work fine, so they are eliminated.  You can check that connectivity straight to the modem.  Once you KNOW those cables are good, then put the switch between the modem and server.  Does it still work?  If so, then you can check each port to eliminate those as problems.

Use the KISS method.  Many times when we get knee deep in troubleshooting, we become our own worse enemy by not reconfiguring everything back exactly as it was before whatever test we did, thus introducing new problems that might mask the true issue.

Author Comment

ID: 13412344
So your saying the cable modem has a DHCP server built in?  The cable modem was set up by the cable company and I'm not to sure how to access the interface.  It's usually right? Why am I setting the internal gateway of the modem to  What is that pointing to?  Now when you say give the server a static IP of you mean go to the  TCP/IP settings for the NIC that is hooked to the switch, right?

I also get confused about DNS.  Do I have to set this up somewhere?  Why do I have to have a DNS server if my ISP already has one?

Thanks for your help BTW.  I've taken a NET+ class and setup a network, but had no problems.  Troubleshooting is frustrating!!!
LVL 16

Expert Comment

ID: 13412537
Most of the cable modems utilize DHCP to talk to PC's.  It makes it easier for them.  It might be or it could be .1.1.  I picked out the .10.x address range out of the blue, but you can use whatever you want.  Since you are running SBS, you need DNS to be pointing to that.  By default that cable modem will give out the DNS address of the ISP, so either you will need to go in and modify that modem or set all your network settings manually.  If you call your provider I'm sure they will walk you through changing the configuration on it.

Whatever address range you choose, the logical Gateway address is .1.  So if you choose to use as your network, then the Modem interface would need the address.  Yes, when I talk about giving the SBS a static IP address, you go to the Properties of the NIC hooked up to the switch.

DNS.....   OK for a typical home user with only PC's, there is little need to go to other machines at home typically and letting the cable modem hand out DHCP and DNS works fine.  If I query a name, by default I will go out to the ISP's DNS servers for resolution.  This works fine in a non domain environment.

Now with SBS, when this is brought up it is a Domain Controller.  Active Directoy is installed and so is the integrated DNS.  If you workstation tries to join the domain or access shares on the domain, but is using the ISP's DNS server, you will probably get timeouts as the ISP does not know the address of that domain or machine.  Not only is it not listed in the big list in the sky, it is a private ip address and would not show up anyway.  This is why all the workstation DNS settings, either by DHCP or Statically, must point to your SBS server.  This will make all requests go there.  The SBS server knows the address of everything on your domain which is on the private network.  When a web site for example is asked for, it checks it's cache first.  If it is not there, it queries the Internet Root servers and returns the appropriate web page.
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Author Comment

ID: 13412582
Okay, sorry if you're getting frustrated with me, you're getting points no matter what.  Now, don't understand the gateway.  I was taught the gateway is where to send packets if it doesn't know where else to send.  Defualt to the default gateway.  Now, according to your plan is nothing.  So what is a LOGICAL gateway?  And why does DHCP need a gateway?  How do I set the DHCP to have a gateway.  Under Server Management > DHCP > then what?

Okay here are some simple question I am just double checking

I do use staight thru cables as opposed crossover, right?

Gigabit NIC"s are backwards compatible with 100baseT, right?

Every port on my switch is identical, right? (i.e. The server doesn't have to be in a special port)
LVL 16

Accepted Solution

samccarthy earned 2000 total points
ID: 13412704
Gateway is Gateway is Gateway......  So, if you enter a static IP in your Nic, the Gateway is, as you said, where to send packets if it doesn't know where else to send.  Now whether the machine gets it's IP from DHCP or from a Static Entry, the Gateway address is the exact same.  So, when you want www.fred.com, you are telling your machines, "Hey I want to go to www.fred.com".  Your machine then looks at it's DNS entries and goes out to DNS, lets say it's  The request goes out to  Your switch sees the address and says, "Hey, that is attached to port 1 and sends it down that line where the server is attached, using address  The Server returns say, for the IP address for www.fred.com to the workstation.  Now the workstation says, "I know where www.fred.com it so lets go to  Since this is Not on your network, the Workstation sends it off to the Gateway, who sends it off, and so on.

In your DHCP settings, you will have options under the DHCP scope you are using.  Actually you have Server Options and Scope Options.  There you can put in the Gateway (It will be listed as Router), DNS Servers, Wins, etc.

You will use straight through cables.  The only time you will use a crossover is say between a router and another router or a switch and another switch.  Now a days most have an uplink port that acts as a crossover if you need it or has an automatic sensing capability for whatever type of cable is used.

Gigabit nics are backwards compatible.  Good Choice!

Every port on the switch is identical unless it specifically says it is an uplink port.

Everyone has to learn somewhere!  Trying to find problems with so much going on can really be trying at times.
LVL 16

Expert Comment

ID: 13426463
Thanks and Good Luck!!

Author Comment

ID: 13426711
i'm putting up another question on the basics of exchange...please resond to it....
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Expert Comment

ID: 13428340
I'll look for it.

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