Automatic IP Address Problem

This might help....

http://www6.nohold.net/Cisco2/GetArticle.aspx?docid=30876a76bd944c51b26463cb077b6cf3_4033.xml&pid=80&converted=0

After changing to DHCP, did you flush the dns "ipconfig /flushdns" system. and then do a "ipconfig/ renew".

Thanks for your input.

For the past five years all six computer had been working with an Automatic IP config setting using a Cayman DSL 3220-H Modem through a HP J12611B AdvancedStack Hub-16U Multiport Repeater. The IP conflict problem occurred after AT&T replaced the Caman DSL Modem. I thought the problem might be the HP Hub so I replaced it with the D-Link switch. This did not solve the problem.

Without making any changes in the IP Automatic setup the next think I did was to physically connect only one computer to the D_link switch. It worked and the Internet was accessed successfully with out any changes in the Automatic IP configuration. When the second computer was plugged into the switch the IP conflict error displayed when I attempted to connect to the Internet. I tried several other computers and got the same IP conflict error message.

To get Internet access I assigned a static IP addresses to each computer. I need to find out why the Automatic IP method is not working so I can reset all of the computers to Automatic IP.

Marv

Your dhcp server may have a restricted number of ip that it can serve. You could also chech the subnet mask for the dhcp

Your comment about the restricted number of ip addresses may be the answer to this problem.

If what I just learned from your comment plus my searches on the Internet the IP's that are assigned by the DSL router come from a server not the DSL Router. The router distributes the ip addresses via DHCP. Is this assumption correct?

Therefore AT&T must have made some changes to our DSL service. The Cayman DSL router did not fail but after AT&T changed the number of IP address to one the problem occurred.

Since the DSL service is provided to our SCORE office by the (SBA) Small Business Association via a govt contract with AT&T I may not be able to make any changes in our DSL service and have to live with static IP addresses.

Thanks to everyone who responded to my question.

Marv

I tried to find some manuals, but I could not. I saw a hint of a management unit and the ability to provide backup if a link should fail but no info. Sometimes the latter is used for load balancing.

The Router gets an IP address from the ISP that's on the public side. It can get this via DHCP or it can be static. I do believe the switches/router that can handle multiple IP addresses has to be smarter.

On the private side, you can have a DHCP server. It does not have to be the the router, but it typically is. the DHCP server in the modem can be turned off. At home, I operate my modem in what's called bridge mode. Another router handles the DHCP.

Here is an example of a Load balancing router. http://www.edimax.com/images/Image/manual/Wire/BR-6624/BR-6624_M.pdf

I've had a quick look at the user manual and it looks to me like this ADSL modem is just that a modem and not a router. If this is the case than the unit has no DHCP server or other routing function.

In this case the static subnet that you have developed is there because of your setup and not because of any registration process.

If so you have two options: add a SOHO router to perform these functions (but you will need to create a second, different subnet - one subnet between modem and router and the second for the office PCs) or purchase an new router with the DSL interface incorporated (requiring only one subnet -DHCP generated - simpler but more costly and will leave you will surplus gear).

Replace the switch with a multiport router...

or

Put a router in between the switch and the DSL modem

Putting the multiport router in there will effectively give you a better firewall and mini DMZ. The DHCP function of the router will ease your woes.

How many computers do you have connected?

Yesterday I learned what caused this problem and how to solve it.

The 2201 Motorola DSL gateway that was installed by AT&T has the DHCP function modified or disabled so the device will only offers one ip address.

The solution was to install a D-Link router with DHCP capability between the gateway and the switch.

All five computers have now been set for Automatic IP address. Problem solved.

Thanks for all your suggestions.

Marv