ICS DHCP allocator stops

[Guest]

Hello,
I have been using ICS on a home network successfully for a couple of months
now, but in the last week, a problem has appeared. Two laptops that connected
successfully via wireless (Netgear WGT624 with DHCP disabled) previously now
cannot get a valid DHCP address from the DHCP allocator running on the ICS
host. These machines worked fine until last week. A third laptop can still
connect properly. I fixed the problem temporarily by disabling ICS, rebooting
all network devices (router, Ethernet switch, ICS host) and then re-enabling
ICS, but within 48 hours, the network has failed again.

If I manually set up TCP/IP on the failing devices, they can successfully
connect throught he ICS host. There are other devices on the network using
fixed IP (print server, Netgear wireless AP/router, two PCs without internet
access). These were set up per microsoft guidelines and as said earlier,
everything worked up until last week.

All the PC's are running XP, (Pro or Home) SP2 and are completely up to date.

If I look at the log file on the failing systems, there is a log entry
showing the systems received a DCHP Nak. Since ICS desn't allow any
configuration or monitoring of the DHCP allocator, I can't see what is going
on on the host side.

Any ideas where to look?
Thanks,
Jim

 

[Steve Winograd [MVP]]

Hello,
I have been using ICS on a home network successfully for a couple of months
now, but in the last week, a problem has appeared. Two laptops that connected
successfully via wireless (Netgear WGT624 with DHCP disabled) previously now
cannot get a valid DHCP address from the DHCP allocator running on the ICS
host. These machines worked fine until last week. A third laptop can still
connect properly. I fixed the problem temporarily by disabling ICS, rebooting
all network devices (router, Ethernet switch, ICS host) and then re-enabling
ICS, but within 48 hours, the network has failed again.

If I manually set up TCP/IP on the failing devices, they can successfully
connect throught he ICS host. There are other devices on the network using
fixed IP (print server, Netgear wireless AP/router, two PCs without internet
access). These were set up per microsoft guidelines and as said earlier,
everything worked up until last week.

All the PC's are running XP, (Pro or Home) SP2 and are completely up to date.

If I look at the log file on the failing systems, there is a log entry
showing the systems received a DCHP Nak. Since ICS desn't allow any
configuration or monitoring of the DHCP allocator, I can't see what is going
on on the host side.

Any ideas where to look?
Thanks,
Jim

Perhaps the two laptops are sending DHCPREQUEST messages requesting
specific IP addresses (as described in Section 3.2 of RFC 2131), and
the DHCP allocator can't allocate those addresses, hence the DHCPNAK.
That would happen, for example, if the laptops requested addresses in
a subnet other than 192.168.0.x. Do the laptops ever connect to
another network? Could there be a rogue DHCP server on your network?

Does disabling and then enabling the laptops' network connections
help?

Running a packet sniffer like Wireshark (Ethereal) should help find
the problem.
--
Best Wishes,
Steve Winograd, MS-MVP (Windows Networking)

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