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DHCP not able to get IP address from server Why?

when ever i manually configure IP address it works but internet speed is approximately ZORE

when ever i choose DHCP to assign me IP address ...it is not able to assign IP address

And it give me a IP address like 169.xxx.xxx.xxx

i have tried all possible way including reinstalling windows emptying TCP/IP stack etc

but result is same

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Belongs to superuser.com – pmod Jul 8 '10 at 6:30
There really is not enough info here to do more than guess and wave one's hands frantically in hopes that might help. If you don't provide any information at all about the network your computer ... is it a computer BTW or some other network device such as a router?? ... is connected to then only &deity. has the omniscience required to answer your question. – irrational John Jul 8 '10 at 14:37
-1 for ZORE.... – Hello71 Jul 17 '10 at 20:57
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migrated from stackoverflow.com Jul 8 '10 at 9:39

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5 Answers

up vote 3 down vote

Internet speed is not affected by getting an IP from DHCP or manually assigning it. There is not enough information in this post to assess why a DHCP attempt is failing.

If this is a home router, power cycle it. Those things get cranky, especially with age.

If you really want to investigate, some things that you'd need to know: * If you assign yourself a manual IP and default gateway, can you ping your DHCP server? * How far does the DHCP request get? (Where does it fail? Is the DISCOVER never acknowledged, or does it fail later?) * Is the DHCP request succeeding, but sending back invalid information? (I've seen bogus netmasks given back by DHCP servers.)

The 169.xxx.xxx.xxx is probably a link-local address (I'm guessing, since you masked out too much information...) If this is a link local, it'll be 169.254.???.???. Link-local addresses are usually found when DHCP fails - they're a last ditch attempt at getting an IP, but they won't get you internet. (You probably lack DNS, and link-locals can't be routed to the internet)

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Any address beginning with 169 is always an APIPA IP address. It's a temporary address given to a machine when the machine cannot get an IP address from a DHCP server. This address is given when the machine contacts the DHCP server but the DHCP server either lacks addresses to give or the system admin possibly has blocked the machines MAC address from receiving an IP, etc. The DHCP server is working... However we cannot fix the problem as we do not have access to the server. – anon31097 Jul 8 '10 at 13:15
@m00st: Any address beginning with 169 is not always a link-local, or, as you call it, "APIPA" address, a point I addressed originally in the answer. Link-locals ("APIPA") falls only within 169.254.0.0/16 - a much tighter range of addresses. – Thanatos Jul 9 '10 at 5:00
when ever i assign IP address manually i am able to ping DHCP server but its takes a long to reply back and one thing i want to mention when i assign IP address manually i m not able to browse anything – STUPID PROGRAMMER Jul 9 '10 at 6:01
@stupid...: DHCP not only gives you an IP, but it gives you routing information and DNS servers. You'll have to set the latter 2 up manually as well. If you're in Windows, they're in the same spot. Routing is usually just a default-route to your router, usually something like 192.168.0.1, and a DNS server - often the router, not always. 8.8.8.8 works (Google's public DNS server) – Thanatos Jul 10 '10 at 21:28
@stupid...: As for your DHCP - are you using just a typical home router? What is your network setup like? – Thanatos Jul 10 '10 at 21:29
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up vote 1 down vote

The address you are receiving is an APIPA address. This type of address is given when your computer is unable to receive an address from the DHCP server... All the work you did on reinstalling the TCP/IP stack was a waste of time. What you need to do is check your DHCP server to make sure it has enough addresses to give out. Also follow DHCP packet streams (Use Wireshark) to see if you getting any dropped packets. If you receive a NACK packet you know the DHCP server is working right, chances are there are multiple addresses on the network and the scope of IP's needs to be increased.

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I have tried all possible method i have 3 lan card in my computer all are connected with a switch and switch is connected with a routed .All of them(Lan Cards) are getting same ip address from DHCP Server My laptop is also connected with the same switch(it is a wired connection i have tried wireless too ) and it gets IP Address from DHCP – STUPID PROGRAMMER Jul 9 '10 at 5:38
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up vote 1 down vote

It was the RJ45 jack! For some reason (carbon on the wires?) it wasn't making a good connection so DHCP couldn't see it and assign an IP.

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If you were able to get online using that cable with a static IP, the problem was not the cable. Something else also changed. – goblinbox Mar 20 '11 at 19:35
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up vote 0 down vote

could possibly be an over zealous firewall blocking port 67/68 (forget which one requests initially). But as Thanatos points out there is not quite enough information to troubleshoot fully. Could we possibly have your operating system, wired or wireless and whether it is a home router or a enterprise style domain?

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up vote 0 down vote

In addition to the other suggestions here about checking the DHCP server, etc., I also suggest:

  • Trying a different network cable, even if the link lights are on.
  • Checking for the latest drivers for your network card (obviously you'll need another computer to download and to physically copy them onto the problem machine)
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