DHCP giving errors on static IP

I believe it's the dhcp, can't seem to figure out. The office has about 35 computers and most of them dynamically set-up IPs. A few computers cannot access the Internet unless you manually input the IP and DNS. And that works for three to four days until you have to renew the IP and input a different address. What could be the problem?

From serverfault $pageUsers[$entry.posts[0].author].name

• It is probably that your DHCP server is not setup to give out enough IP addresses. Expand the DHCP range on your server and you should be fine.

  From Jason Berg

• What are you using for your DHCP server? Is it a Windows server of some type, or is it your router?

  I'm betting it is your router, because it sounds like the router is blocking access from IP addresses that it has not asigned, or that are outside its range.

  What model router do you have?

  If these questions are all foreign to you, we can start more basically... what is the output of the command "ipconfig /all" on a machine that is working properly? ie, one of the machines that you do NOT have to futz with every couple of days...

  Post it back, and I'll give you some more to troubleshoot with.

  HTH,

  Glenn

  From Glenn Sullivan

• Agree with Jason on this one. First thing to check is the DHCP Scope and make sure you have a sufficient ip address range to service all of the clients.

  From joeqwerty

• Do you have multiple dhcp addresses for systems that require static addresses? They expire, so the next time it happens, check allocations to see if you have any doubles. If so, you'll have some fun reading to do on dhcp lease expiration (I'm sure there are a few questions here detailing the broad strokes)

  From Kara Marfia

• Also make sure your DHCP range is not overlapping with addresses that are statically configured. Most DHCP servers will detect this and diable the address from being given out again.

  If your have no or bad IP documentation I recommend you download the nmap utility and run it like this (assuming you use 192.168.0.0/24 network)

  nmap -sP 192.168.0.1-254 > myNetwork.txt
  

  Now you can start to document.

  From JGurtz