This is hard, I challenge you!! I keep having this
repeated problem on several machines and several different
configurations at different times. Basically, when I
change something major, like add a new network interface
card, I cannot talk to anything: the new interface cannot
find the DHCP server, and Windows (demonstrated on XP and
2000) uses a autoconfiguration IP address (169.something).
I have searched everywhere and cannot find a reasonable
explanation for what is happening. Here are my different
circumstances:

(1) laptop (Win 2000) connected directly to cable modem,
all is good: internet connection works fine. I moved the
cable from the laptop to my desktop (XP): the desktop does
not obtain an IP address resulting in no communication
with anything. IP address is 169 address and upon
ipconfig /renew, the error DHCP server not found results.
See below for ipconfig output. The fix for this case was
to power cycle the cable modem.

(2) I installed a wireless router, and everything was fine
using the wired connection with the same NIC. I installed
a wireless NIC. The wireless link came up no problems.
Same results as in #1: no IP address, autoconfiguration IP
assigned, DHCP server not found. Fix for this case:
research problem for 2 days, come back to computer to try
a few things and boom, IP address is fine 192.168.0.x
through router and all is good.

(3) Totally separate network at work: new computer wired
into ethernet drop in my office ... everything fine (DHCP
assigned address, all comm good). Moved this computer to a
lab where I connect same NIC to 8 port switch that
ultimately gets to a router on the same company network.
Same result as #1 and #2: no IP address, autoconfiguration
IP assigned, DHCP server not found. Fix for this case:
assigned a static IP and I can talk to router (this didn't
work for other cases).

There MUST be a common thing happening here, but I haven't
found a good explanation for it. It was explained to me
that in case #1 that the modem associated the MAC address
of the original laptop with itself (or something like
that) and it needed to be powered cycled. What is this
association (ARP cache on the modem?)? Is a similar thing
happening in the other cases?

I would appreciate any and all help!!! This one keeps
coming back to me and yet there is nothing I can do about
it each time it happens!! THANK YOU!



Here is the similar output for each case of ipconfig /all,
ipconfig /renew, and arp -a:

C:\>ipconfig /all

Windows 2000 IP Configuration

Host Name . . . . . . . . . . . . : viper
Primary DNS Suffix . . . . . . . : xxx.xxx.com
Node Type . . . . . . . . . . . . : Broadcast
IP Routing Enabled. . . . . . . . : No
WINS Proxy Enabled. . . . . . . . : No

Ethernet adapter Local Area Connection:

Connection-specific DNS Suffix . : xxx.xxx.com
Description . . . . . . . . . . . : Intel(R) PRO/100 VE
Network
Connection
Physical Address. . . . . . . . . : AA-BB-CC-DD-EE-FF
DHCP Enabled. . . . . . . . . . . : Yes
Autoconfiguration Enabled . . . . : Yes
Autoconfiguration IP Address. . . : 169.254.235.62
Subnet Mask . . . . . . . . . . . : 255.255.0.0
Default Gateway . . . . . . . . . :
DNS Servers . . . . . . . . . . . :

C:\>ipconfig /renew

Windows 2000 IP Configuration

The following error occurred when renewing adapter Local
Area
Connection:
DHCP Server unreachable

C:\>arp -a
No ARP Entries Found

Hi Dave. Thank-you for your post.

Since this happens on different networks it sounds like it could be an
issue with the client. But it really sounds like the clients DHCP requests
are not making it to the DHCP server.

In the case of your network at work, the symptoms that you are describing
really sound like a configuration issue on the switch. Don't laugh just
yet...but the most common cause of the symptoms that you are describing is
that the spanning tree algorithm is enabled on the ports that you are
plugging your laptop into. When you plug your laptop into such a port, it
may take a while for the port to initialize. During this time the port
will not switch traffic to/from the laptop. Your laptop is trying to get a
DHCP address during this same period, but can't because its traffic is not
being switched to the network where the DHCP server resides. You will end
up with an APIPA address. On most new gear this should not be a problem
though.

168455 DHCP Renewal Failures on Switched Networks
http://support.microsoft.com/?id=168455

A very handy tool for troubleshooting issues like this is dhcploc.exe.
Simply run <dhcploc.exe client's_IP_addr> Make sure you specify your
client's current IP address not the DHCP server's address. You should use
a routable IP address for this test rather than an APIPA address. When it
runs you will see a blank screen. Every time you press the 'd' key, it
will send a DHCP discovery message and will display the server details of
any DHCP server that responds. Using this along with network monitor you
will see if the client's request is making it onto the wire and if the
server is responding, etc. Press the 'q' key to exit dhcploc. Dhcploc is
in the NT Resource Kit.

http://www.microsoft.com/technet/tre...hnet/prodtechn
ol/winntas/support/advtshoot/x0a_tool.asp

Other possibilities: do you have any IPSec policies limiting traffic
to/from the network? Do you have any filter drivers installed like
personal firewalls, etc? If so, disable them and test...

I hope that helps.

Tim Rains
Product Support Services
Microsoft Corporation

This posting is provided "AS IS" with no warranties, and confers no rights.

Thanks Tim. The DHCPLOC tool will certainly help the next
time this happens or if I can reprocude the problem. As
for your additional possibilities, I do have VPN software
on one of the machines in question, but not the other (I
assume the VPN software is using IPSec). I do not have
additional personal firewalls, only the hardware router.

Dave
>-----Original Message-----
>Hi Dave. Thank-you for your post.
>
>Since this happens on different networks it sounds like
it could be an
>issue with the client. But it really sounds like the
clients DHCP requests
>are not making it to the DHCP server.
>
>In the case of your network at work, the symptoms that
you are describing
>really sound like a configuration issue on the switch.
Don't laugh just
>yet...but the most common cause of the symptoms that you
are describing is
>that the spanning tree algorithm is enabled on the ports
that you are
>plugging your laptop into. When you plug your laptop
into such a port, it
>may take a while for the port to initialize. During this
time the port
>will not switch traffic to/from the laptop. Your laptop
is trying to get a
>DHCP address during this same period, but can't because
its traffic is not
>being switched to the network where the DHCP server
resides. You will end
>up with an APIPA address. On most new gear this should
not be a problem
>though.
>
>168455 DHCP Renewal Failures on Switched Networks
>http://support.microsoft.com/?id=168455
>
>A very handy tool for troubleshooting issues like this is
dhcploc.exe.
>Simply run <dhcploc.exe client's_IP_addr> Make sure you
specify your
>client's current IP address not the DHCP server's
address. You should use
>a routable IP address for this test rather than an APIPA
address. When it
>runs you will see a blank screen. Every time you press
the 'd' key, it
>will send a DHCP discovery message and will display the
server details of
>any DHCP server that responds. Using this along with
network monitor you
>will see if the client's request is making it onto the
wire and if the
>server is responding, etc. Press the 'q' key to exit
dhcploc. Dhcploc is
>in the NT Resource Kit.
>
>http://www.microsoft.com/technet/treeview/default.asp
url=/technet/prodtechn
>ol/winntas/support/advtshoot/x0a_tool.asp
>
>Other possibilities: do you have any IPSec policies
limiting traffic
>to/from the network? Do you have any filter drivers
installed like
>personal firewalls, etc? If so, disable them and test...
>
>I hope that helps.
>
>Tim Rains
>Product Support Services
>Microsoft Corporation
>
>This posting is provided "AS IS" with no warranties, and
confers no rights.
>
>.
>