On 6 Dec 2006 at 21:34, Tom wrote:

> Currently first computer is using a 56K INTERNAL USR DIAL-UP MODEM. Am
> told the second computer should be able to connect through the first
> computers modem but could never get it to work. When the first
> computer is online the second one SOMETIMES tells me it is online too
> and shows the speed of the internet connection, but can't open any web
> sites. Can ping the first computer from the second but can't ping the
> second from the first. Same for net view command. Can ping various web
> sites from the second computer but can't open any web sites. 

  DHCP (Dynamic Host Configuration Protocol) is a wonderful thing for 
running a network.  One machine is designated as a "DHCP server", and has a 
statically assigned IP address.  Machines that are clients (have "Obtain an 
address automatically" checked) send out a special request for address 
information, and the DHCP server tells them what numbers to use.

  The.  Singular.  [You'd want two DHCP servers on a medium-to-large network 
in case one crashed; special care must be taken so they don't step on each 
others' toes.]

  Your NetGear router, fresh out of the box, provides DHCP service to its 
LAN ports.  How convenient!

  When you enable ICS (Internet Connection Sharing) on a Windows machine, it 
gets configured as a DHCP server.  Clients who get their addressing 
information from the ICS host will have what they need to use it as their 
gateway to the rest of the world.

  So it sounds to me like you've got two DHCP servers on the network, each 
of which *assumes* that it's the only one.  It's quite possible that the 
information they're offering to clients is not just incompatible, but 
actively in conflict.

  Since your PC with the modem is the ICS gateway, plug the *WAN* side of 
the NetGear into that PC, and configure it to get an address from DHCP.  You 
may need to change the LAN side address of the NetGear so it's not seeing 
the same address range on both its WAN and LAN sides.
  When you are ready to connect to cable, DSL or whatever, turn off ICS and 
plug the PC which today had the modem into one of the LAN ports and make 
sure "Obtain an address automatically" is checked.

David Gillett

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