DHCP Thread

mac_cnc

mac_cnc

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Oct 14, 2000
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Ok i've convinced the boss to move over to DHCP. Im testing it on my machine now but for some reason my machine will not connect to the DHCP server. I have authorized the DHCP server in AD and it appears to be working but I still have no joy. Any thoughts?

Oh im on an XP Pro box and the server is 2000 advanced
 
Are you on the same subnet as the DHCP server? Have you created and activated a scope?
 
Yes I created a scope and the machine's subnet would be set by the server would it not? But yes, before DHCP my machine was in the same subnet.
 
As for being on the same subnet, I'm talking more of a physical, layer-2 kind of way. DHCP is a broadcast protocol, and therefore you have to be on the same hub, switch, or Vlan in order for it to work. Otherwise, you need to have a helper address on the client's router interface that will forward the broadcast of the DHCP request from the client to the server on a different subnet. So no, in reality the DHCP server does not determine what subnet a client is on. The router and physical topology of the network determine the client's subnet. The DHCP server simply responds in kind.

Perhaps a little more information on your specifics would help. What is the DHCP server address? What are the scope properties? How are the server and client connected to the network?

Good Luck!
 
If you are on a small network, i highly recommend sticking with static. It can make tracking down problems much easier.
 
I agree with Sticky, Static in the house is much easier to track down which comp needs what open or what looked at or taken off the network cause its going skitzo.
 
I concur, nothing nice than a nice static scheme with a nice network digram of each machine, it's IP/hostname info. I set up a range for printers to be in, access points, PCs, laptops, and then I leave a small range of about 20 for DHCP so that students can bring in laptops and other one time mics. devices.

It makes life so easy to audit the network and see which devices belong and which don't as well as knowing the IP of each machine right away for remote desktop/ssh connections. Static is harder to setup, but it's easier to run in the long run if you plan it properly.
 
I would agree with above posters; at home I use a dchp to address static addresses to my pc's based on their MAC address, which works well.
 
A buncha foolishness... DHCP is WAY better... I've got roughly 80 devices and all are running DHCP with no problems... zero maintence, and I don't have to remember where I left off for IP's when I add a new machine, or when a wifi laptop walks into the building, it just works.

Want to know which machine's got what IP?? No problem... go into DHCP and look... not like it's a big deal or something.

QJ
 
Ok thanks for the help folks but I have 40-50 machines that need this and finding the IP to give the next one sucks. I have 2 switches by the way. 3com Superstacks 3226. Is there something I need to do within the switches to allow the communication to take place?

Thanks to all who helped.
 
QwertyJuan said:
A buncha foolishness... DHCP is WAY better... I've got roughly 80 devices and all are running DHCP with no problems... zero maintence, and I don't have to remember where I left off for IP's when I add a new machine, or when a wifi laptop walks into the building, it just works.

Want to know which machine's got what IP?? No problem... go into DHCP and look... not like it's a big deal or something.

QJ
Click to expand...
Sure you got them running right now with no problems, leave that network up for a few years, some of those systems and machines aren't going to be online 24/7/365, as soon as 2 machines drop off for more then 24 hours, BAM ips start changing, power outage? Same problem, thats when I gave up on DHCP. I also like the fact for static I jacked my servers network cable to play Xbox, 40 days later, plug it back into the Server and BAM its back online, don't have to reset IPs because another machine stole it.
 
:mad: Can we please try to help with my issue instead of fighting over static vs. dhcp ??

I am going with dhcp for now and if it doesnt work then it'll be my problem. :eek:
 
My next step would be to install Ethereal on the client and watch the DHCP handshake. Either your client is or is not getting a response from the DHCP server. If it is, it doesn't like what it's hearing.

Also, check the logs on the DHCP server itself for clues.

(BTW - DON'T use lease reservations for Domain Controllers. They need to be really static, not just psuedo-static.)
 
It just isnt picking up the address. I cant figure it out. I think I may not be on the same switch as the server...which in that case how can I make both of them talk to each other. I mean they already do, but someone mentioned earlier that they may not be in the DHCP respect.

:confused:
 
Holy CRAP! A bunch of people don't know how to read. This isn't for at home, it is for a Corprate network.

Someone mentioned running out of IP addresses. This is easy to fix. Figure out how many devices are going to be getting thier address via DHCP, then triple it. You may need a Class B scope, you may not. I have 50 machines on one network, and another 10 on another network, and a third network with 5 machines. Each one using DHCP. My scope for the Corp Office network is 150 addresses. The two branch offices have scopes of 50 addresses. Most Network Admins/Engineers plan things out prior to rolling them out (At least those that like getting a pay check do).

Ok, now on with the fun. One thing to try, is plug your computer into the same switch as the server is in, see if it gets an address. If it does, then it must be with the config between the switches. If it does not get an address, then it is either your client or the server. It could still be the switch config, but it is less likely. If you have an old hub (do this part on the weekend when no one is there), hook the server into the hub, your computer into the hub, and the hub into the switch. For fun and giggles I would hook up a box running Ethereal into the hub also.

If you get an address on the hub, then you KNOW your server, and desktop are working correctly. At that point it is with the switch configuration.

After a quick web search, the 3com Superstack 3226 is a layer 3 switch. You most likely will need to change the config on that switch. After looking at this: 3Com SuperStak 3226 Datasheet It has a DHCP Relay built in, so you will want to configure that.

Unfortunatly I can't help with that, as it has been a long time since I worked with 3Com switches. I don't remember the command for it. I would guess you have to SSH or Telnet into the switch, then en for enable, then see what you can find. I know my HP switches have nice text menues to help out. Good luck!
 
Thanks for the informative and helpful comments in that last post. I will hit up the 3com manual and see what there is to be seen. I will try everything else this weekend. I have 180 usable DHCP addresses by the way so I should be fine. :D
 
One of the things I did when I got to my current job 5 years ago was redo the DHCP scope and write everything down. I made Addresses .1 - .15 network items (switches, routers, etc). Everything from .200 - .220 are printers, Servers are .221 - .254. Test equipment is .16 - .25. DHCP scope is .40 to .199, so I have a bit of room to play with in each area. I also moved our firewall from .245 to .1

This has made my life a lot easier. If I have something that needs a static IP, I know where it is going to go, and I document what it is, and where it is in a spreadsheet. I used to have that spreadsheet hung up on my wall. Now I just have a network diagram with the same info hung on the wall.
 
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