sundance-communications.com/forum Forums VOIP Phones & IP PBX Networking Network Hobbyist Question.

I enjoy tinkering around and learning new things about computer networking so please bear with my ignorance.

Today a friend ask me to hook up a secondary router as an access point in a different part of his house because he had a very low signal in a remote part of the house.
I took an old wireless router and installed it in a room in the other end of the house via a hardwired cable.

I managed to get it to work by following the instructions per this link. My question is: Is it really necessary to dummy the IP addresses as shown in step number 3?
Also, why must you turn DHCP off in the secondary router?

It works so he's a happy camper but I like to know why this setup works and also if there are better ways of doing this.

Bobby, you can't have two DHCP servers on the same LAN. Also, on the second device, don't bother using the WAN/Router port. Just bring your cable into one of the switch ports. You'll just be using it as an extra Wireless Access Point on the same LAN. You don't need to give it any more credence than that.

I'm no pro by any stretch of the imagination on this subject, but I managed to set up a wireless access point in my house for the same purpose. It actually worked.

The reason that you only want one device with DHCP enabled is that you only want one of them (preferably the main router) to dish out IP addresses. This ensures that each connected device behind it will receive a unique 192.168... IP address and subsequent private communication via a common network.

If both routers had DHCP enabled, then it would be possible for two remote devices to receive the same 192.168.... IP address. The separate routers would not know any better since they hand out IP addresses upon request from any connected device upon request when DHCP is enabled.

Two devices sharing the same IP address would be about the same as plugging two digital phones into the same port. If it works, it will be marginal at best and only for a few minutes.

EDIT: As Ed wrote the book, Trace answered the question in half the time!

To add to what was already said above.

You only want DHCP to be handed out by the Main router. Second to the reason that Ed gave you is that in consumer grade routers they are generally not able to be set to hand out a differnt default gateway than its own Lan IP.
If you had 2 routers handing out DHCP in the example on that site one would hand out default gateway .1 and the other would hand out default gateway of .2 which is not connected to the internet.

Also to expand on the consumer grade routers. Some routers do not tie the Wireless side of the router directly to the lan side of the router. In this case you cannot pull DHCP from the lan thru to the wireless side of the router. It is not likely that you would see this but just a little info for checking when you do have that situation.

Third of all. If you are at a buisness that is handing out DHCP on there Microsoft server it will disable it self when seeing another DHCP source on the network. Then you have to disable it in the router and turn it back on in the server.

As for setting the 127.0.0.1 IP on the Wan port. It is very rare that you need to set this. The only thing that it is there for is most equipment uses 127.0.0.1 as its internal IP address. It would be to route things to itself. If you go to a dos prompt on your computer and type "route print" you will see a route statement 127.0.0.0 255.0.0.0 127.0.0.1. This is an internal interface on your machine that allows for internal networking basically.

Hope this helps explain things a little more.

You actually can have multiple DHCP servers on the same lan under certain conditions, generally not applicable to home networking.

I manage the network for a networking lab at the local community college. I have two DHCP servers on the lan, configured as a redundant pair, with failover. Both servers have identical configurations, with the exception of the failover relationship. The servers will split the dynamic address pool, and each one will assign from their portion of the pool, and pass state information to the other server. If a server goes offline, the other server will continue to function, and will take over the remaining portion of the pool after the failover timeout expires.

If you have your DHCP servers configured to only hand out staticly assigned addresses, you can have multiple servers, as long as you have non-conflicting address assignments, and you get the authoritative bit set correctly. You want to set the servers so that they are not authoritative for the network, so that they do not send DHCPNAK's when they cannot assign an address.

Of course, my experience is with unix systems, which behave as documented, and allow the admin to actually configure them. I would not even try this with windows servers.

That senerio is a little different than what I stated above.

I was describing Windows Servers. Most people use windows servers which if they do see another DHCP server on the network and that dhcp server is considered a higher power then it will turn itself off. If I am higher then the other will turn itself off.

Example
Windows 2000 server verse Windows 2003 server. Both have DHCP enabled Windows 2003 server will win. Windows 2000 server will turn itself off until a reboot then it will look again and turn itself off if needed. If a router is configured for DHCP with windows 2003 server is configured for DHCP. Windows will turn itself off. I do say turn itself off because when it reboots it is back on until someone actually disables the service.

This is just for informational purposes.

I am not here to get in an argument over unix verse windows. I am not very experienced with unix and know that every platform has it place. My world is mainly Windows Platforms with a little unix.