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Static IPs and DHCP

Posted on 2003-11-10
Medium Priority
Last Modified: 2010-03-17
I need to setup a small home office and I need to have a static IP address for each client machine. My cable provider can give me bundles of static IP addresses. Here's the situation: I do NOT want to define the IP address for each machine. I want each machine to get the IP address dynamically (I don't care if it changes the next time I boot as long as the address is one of the addresses given by the provider). I wasn't planning on using a server. Is there a piece of hardware that I can connect to the cable modem which will act as a DHCP server where I can define the range of addresses I have? With this device, the client machines should be able to get the IP address dynamically and I can still guarantee that this IP address is within the pool given by my provider. I'm looking for a solution that's cheaper than getting a full server machine with an operating system.

Question by:hsaqallah

Expert Comment

ID: 9717722
 yes there is a dsl router is what you need...
this one is d-links and only 25 bucks...
just plug the cable modem into it and configure your static ip address gateway and dns info and thats it it had a built in dhcp server to assign ip to your clients automatically also here is one with print server for 35 bucks


 hope this helps you good luck

 if you need more info just post here

Expert Comment

ID: 9724211
I agree, most routers now have build in DHCP services built in without having another box. I have a netgear RP614 that gets an ip from the cable company (its analog cable, so I stil have a DHCP lease) then it hits my router and distributes an ip in the range of to 192.168.0.whatever I have defined in my subnet mask up to 255 I cant remember exactly, to all the ethernet devices that are connected. The subnet mask is where you define the range distrbuted IPs if im not mistaken and you need to set the default gateway. They will all probably stay in the C class reserved ip range which is 192.168.xx.xx. again im not 100% positive, someone You can also configure all kinds of neto stuff with ease, and best of all, if you mess it up, your only a paperclip away from getting it to work again.

Hope it helps


Author Comment

ID: 9724892
Hi guys,
It looks like I misrepresented the problem. When I said static IP, I meant universal static IP addresses, and NOT address in the range of 192.168.x.x. The latter range is for the private network and it hides the machines on these network from the outside world. That's not what I want (I know it sounds strange).
To help explain the idea better, look at the diagram on this page:

For the sake of this question, ignore the fact that a wireless connection is used. The question I'm asking can apply equally to a wired network.
Note that the provider gave the user three 'universal' static IP addresses (i.e. unique on the internet). The two client machines, each got an IP address out of the three ones given by the provider. The easy way to do this is to 'hardcode' the IP address in the TCP/IP configuration on these client machines. However, this is the thing I'm trying to avoid here. What I'm trying to do is to find a device that can distribute the available static IPs among client machines WITHOUT the need to hardcode the addresses on those machines. To elaborare more, one I'm looking for is that I can have many people that would connect to this network configuration. What I want is that when one of them connects to this network, the routing device will pick one of the static IP addresses given by the provider and assign it to the client machine.
The routers I found so far can only assign addresses in the range 192.168.x.x. This has the advantage of hiding the client machine and all the cool stuff that comes with it, but that's NOT my goal here. I do NOT want to hide the client machines, yet I don't want to hardcode the IP address on them.
I hope this explains the problem better.

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Expert Comment

ID: 9725002
hmm ok to achieve this you need better equepment..

this can be done with a cisco pix series firewall but if you only have 3 addresses you will use them in the firewall config alone and end up using nat anyways... you can alwas setup an actual dhcp server ( either microsoft,simple, ect...)
the dhcp would need 1 ip address and then assign the other 2 out to clients..

heres a little pic...

 internet  -----  dsl modem ---- Dhcp Server  1 ststic address
                                              |           |
                                            |               |   dhcp assigned by server
                                          |                   |
                                        |                        |
                                   Cliant 1                   Cliant 2

 i would suggest getting more ip's from you isp for this though...
 hope this gets you pointed in the right direction...

Author Comment

ID: 9725654
Thanks for the info. Getting more static IP addresses from the provider is no problem. I know that some addresses will be used for the device(s) themselves. Also, I want to avoid using a computer machine (like Windows 2000 Server). That's why I was referring to it as routing device. The accepted answer for this question would be to give me the name of the device (like a specific cisco device) that I can check its manual and see if its DHCP server supports a free range of IP addresses.


Accepted Solution

vtobusman earned 400 total points
ID: 9725718
Well then cisco pix 515
                         pix 506
                          pix 520
any of those will work...


Expert Comment

ID: 9725732
as for manuels you might need someone to help program them for you..

 i found lrnmoore here in experts exchange to be of great help in this area..
for questions on cisco equipment post in

  Good Luck

Author Comment

ID: 9725896
The PIX 501 is the one! :)

Expert Comment

ID: 9752461
A small linux server would cost less than the pix router.

Expert Comment

ID: 9761679
best solution that could cost you about $50 by going best buy.   you need Linksys etherfast cable/dsl router.  model #befsr41..  you can assign your computer a static ip .. and the router will know what it is and give them inet access.  if you need more information on how to do this.  just post your msg and i'll responce

Expert Comment

ID: 9846929
I'm interested in henryenr's information. We have an ADSL line with several satic IPs. Our system works as follow:
Internet -> Router(Cisco 827 Series) -> Linux Machine (Web Server) -> 3Com 3300 XM switch -> Hubs -> Workstations.

The configuration may look weird for some people, but thats the way it is now and so far it doesnt have any problem. We have tried to connect from the router to the switch, but it doesnt work, hence no workstation is able to connect to the internet.

With this configuration, the router has one IP and the linux machine has one as well.

The questions are:
1. How do we re-arrange the configuration so that the switch connects directly to the router and the web server is treated as one of the workstation with a static IP (not local IP)??

2. If i want to have another web server, how do I assign a static IP the new server?? I tried to hardcode it, but it didnt work??

Thanks in advance

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