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Old 07-31-2004, 02:04 PM   #1
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Registered: Jul 2004
Location: Minneapolis, MN
Distribution: Slackware 9.1
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How does a hub work?

I have a question about hubs and sharing an internet connection through a hub.

My ISP provides a cable modem which uses DHCP and I recently got my internet connection working on my Slackware 9.1 box. However, I am only able to get connected when I am connected directly to the modem. When I try connecting through a hub (EtherFast® 10/100 5-port Auto-Sensing Hub) and sharing the connection with a Windows box, I cannot get an internet connection and dhcpcd will not pickup my IP and DNS. The Windows box, however, has no problems getting an internet connection. Why is this? I guess I don't fully understand how a hub works and if it is suitable for sharing an internet connection.

Can anyone tell me more about a hub and, if this is suitable, help me troubleshoot the problem.

Thanks in advance.
Old 07-31-2004, 02:34 PM   #2
Registered: Oct 2003
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maybe this will help

Most Internet service providers provide you with a single ip address for your account. if you are connecting a hub it usually will not have routing functionality. Your windows box is picking up the address that your isp is providing you and your Linux box is left without an address. I bet if you go to the console and use ifconfig it will show your eth0 with an address of

You will want to use a router. The routers function would be to take the one address that your ISP provides you and share that address with both of your computers. The router assumes the address that is given to you then provides a gateway for your computers to talk to the internet through. By default most home routers will assign your computer an address from it's own range of ip addresses.

For example your ISP may give you the address your router will use this address and will also have an address like then it will give your computers addresses of it's own. Example and 192.168.1. 4 your computers will talk with the address when ever they want to communicate with the internet. and the router will translate what you want and send it out as if it was from

When you have a hub none of the above is done it simply connects both computers to the modem and which ever computer requests an address from your isp first, gets it. Your ISP will use the machine address from your Network card (a hard coded address) to assign your IP address. DHCP keeps a database of what Machine address it has given an address to and can tell the difference between your two computers. this is why only one gets an address at a time.

I hope I made that clear enough.
Old 07-31-2004, 04:41 PM   #3
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Futhermore the modem remembers the network cards MAC. If you want to connect to the internet with the other PC before you install a router you will need to recycle power on the modem prior to initializing the network card.
Old 07-31-2004, 05:40 PM   #4
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Thanks for your help. That clears things up considerably and explains a lot.


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