Doonz

Just set up a W2K server....to access the interent I need to set a static IP but since I am connected to a cable modem I need to change it every two day to matain the internet access....since I am playing with the server....what recommendations do you guys/girls have to set up DHCP to issue a set IP adress in a certian range so I dint have ot keep resetting it???


What ohter advice do you guys/girls have to setting it up...my ultimate goal is to get it steady enough to use no-ip.com and give it access via FTP...or telent...but that is down the road....

Thanks ofr any advice, education or input you can give:bandit:

johnwill

With a server, I'm assuming you'll have one NIC attached to the cable modem, and the other to the internal network, right? If so, why can't you configure the NIC to the cable modem for whatever is required? I have a client with W2K server and DSL, the NIC to the DSL is configured for the service, and the other NIC has a static address for the rest of the network, works fine.

Doonz

Two thing that mess up the works....beside my stupidity

connecting from cable....to cable modem...to Office connect 3 com gate way to the three machines....

Plus I need to drop another nic in....trying to cheat...thanks john

johnwill

Yep, you don't want the cable modem directly on your internal network, need some buffering there. :)

tcheavey

Yeah, and setting up DHCP reservations is done at the server issueing addresses your server can't say "I want this add." If you install DHCP on your server and authorize it, look out! You'll be giving out addresses to anyone needing a lease as they logon. IT admin might get upset I'm not impliying you would, but we have had students do it at school.

johnwill

Actually, the DHCP handshake has the option of the machine requesting a specific IP address. Of course, the DHCP server has the option of either granting that request, or offering a lease on another IP address, so there's no guarantee that you'll get the requested address. Of course, if you don't get the requested address offered, you can just refuse the lease and not talk! :D:D

Pseudocyber

I'm curious why your server needs a new IP address every two days to maintain internet access?

If a DHCP interface is connected, the protocol should request to "renew" the lease when the lease period is half way expired. For instance - if the lease period is 24 hours, then it should request an extension at the 12 hour mark. Assuming it is able to talk to the DHCP server, the DHCP server should still have the IP assigned to it and there shouldn't be a problem with receiving the same IP address to be extended for another 24 hour period.

If a client and DHCP server are both accessible and on 24/7, the client should, theoretically, have the same IP address indefinitely, without reservations.

If you're running a DHCP domain and you want to make sure a certain machine receives a certain IP address without using static addressing, you would reserve the IP address for a certain MAC address. You would do this in a large network because you can still dynamically assign other networking info to the client even though they always get the same IP - for instance if you wished to change the default gateway, DNS server, etc.

HTH

tcheavey

johnwill, How do you make this request from the client? Cmd line? I don't see that config anywhere in the options. I was just wondering, not that it would make any sense to do. Normally a client would not have any idea of the DHCP add scope.

johnwill

It depends on the client, the DHCP request protocol allows you to request a specific IP address. I wrote a client for an aerospace application, and I wanted a specific IP whenever possible, since some of the diagnostic tools assumed a specific IP.

If you really want to get into TCP/IP architecture and protocols, I suggest the three volume set "Internetworking with TCP/IP" by Douglas E. Comer. It's been my bible for years when I want to find out what's going on under the covers. :)

tcheavey

Well, just for instance with W2K, is it a CMD line thing or what?

johnwill

To be honest, I've never tried to do it with Windows, because it's never been a requirement to have a specific IP address. When I had my embedded processor in the avionics rack, I needed to be able to find it under all conditions. Since we had default IP addresses when the DHCP server wasn't available, I wanted that to be the same when DHCP was running if possible.

Like I said, it's an option when you build your DHCP request packet, but it's not required for DHCP to function. I'm not sure if Windows will allow you to request a specific IP, but I do know that Windows 2000 Server can be configured to bind an IP address to a MAC address.

Pseudocyber

As Johnwill said, the preferred method is to deal with it on the server side, not the client. If you have a machine that you always want to be a specific IP, then you need to make a reservation on your DHCP server.

You still didn't answer my question as to why you need it to change every two days ... ;)

It is my understanding that Windows will "cache" the IP in its registry. When it sends out a DCHP request, it will use this cached IP address from the regisry and request that it receive it. If you're relying solely on the client side, there is NOTHING on the server side that will ensure you actually get it. If the server side doesn't have a reservation, and the client releases it, DHCP is designed to be efficient and hand it out when its turn comes.

Now, as I've said, if your box is running 24x7 and it is theoretically able to reach the DHCP server 24x7, your box, the client, will request a "renewal" of the lease on the IP at the halfway point in it's lease time.

For instance ... the box I'm on at work has this when I type "ipconfig /all":

Lease Obtained. . . . . . . . . . : Thursday, March 20, 2003 4:40:27 PM
Lease Expires . . . . . . . . . . : Thursday, March 20, 2003 9:40:27 PM

Obviously, my lease lasts for 5 hours. This means at 4:40 + 2.5 hrs, it should renew itself and the "Lease Obtained" should change to 7:20 PM. However, I'm not working that late for you Doonz, so I'm not going to test it tonight. ;)

So, your box, if its always on and your DHCP server is always available should always have the same IP. If for some reason, the DHCP server is unavailable, I believe it will request a release every 30 minutes - I could be wrong on that.

But the best thing, again, is to reserve it on the server side. However, if the server is your ISP, this is where paying them the $$$ for a reserved IP address comes in!

HTH :D