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Re: HELP! dhcp server not talking to clients

'nmap -sU -p 67 192.168.1.*' produces the following results.

Starting nmap V. 3.10ALPHA4 ( www.insecure.org/nmap/ )
Nmap run completed -- 256 IP addresses (0 hosts up) scanned in 46.453 seconds

'nmap -sU -p 67 10.0.0.*' produces the following results:

Starting nmap V. 3.10ALPHA4 ( www.insecure.org/nmap/ )
Interesting ports on lewisc (
Port       State       Service
67/udp     open        dhcpserver

The 1 scanned port on lewisc2 ( is: closed

Nmap run completed -- 256 IP addresses (2 hosts up) scanned in 36.155 seconds

This is somewhat expected. is the proper dhcp server. is the Win2000 client machine (apparently it is successfully getting its lease). What is NOT showing up is the printer ( and the Win98 machine (

Apparently they are on the 192.168.1.* subnet, but why did a scan of that subnet not produce anything?


p.s. I just had my wife reboot the Win98 machine (I'm working remotely using the dynamic IP that my ISP provides), and it apparently got the correct lease. I've also had her reset the externel jet direct print server using several methods, but without success. It still is getting from from a dhcp server at!

sean finney wrote:

hey charles, are you sure another machine isn't running a dhcpd?  i
sure don't see 192 addresses in your config...  try installing nmap
and then doing

# nmap -sU -p 67 host

for all the suspect hosts.

On Mon, Dec 16, 2002 at 11:53:00PM -0600, Charles Lewis wrote:
I have dhcp set up on my linux box to serve a Win2000 box, a Win98 box, a WinXP box, and networked HP LJ1200. It works fine, until I try to upgrade the kernel from 2.4.18 to 2.4.20 (from an earlier thread). The machine locks up after a few minutes, so I go back to 2.4.18, and all my machines are getting 198.168.1.x numbers when my dhcp server is supposed to be providing 10.0.0.x numbers. It's very frustrating to everyone in the house because suddenly none of them can use the internet, print, or save files to their samba shares. Now I am not a network guru, so maybe someone can help me spot some problems in my setup.

Here is my dhcpd.conf:

#option domain-name "";
#option domain-name-servers,;

server-identifier lewisc;
option subnet-mask;
default-lease-time 600;
max-lease-time 7200;
subnet netmask {
  option broadcast-address;
  option routers;
  option netbios-name-servers;

host lewisc2 {
  hardware ethernet 00:01:03:E7:48:1F;

host lewisc3 {
  hardware ethernet 00:00:39:F0:9A:C5;

host caleb {
  hardware ethernet 00:A0:CC:D2:A0:73;

host officelj {
  hardware ethernet 00:01:E6:48:69:A2;

When I run dhcpd in debug mode, I get:

Listening on LPF/eth0/00:01:03:dd:22:e0/
Sending on   LPF/eth0/00:01:03:dd:22:e0/
Sending on   Socket/fallback/fallback-net

And it just sits there with no feedback.

When I do a tcpdump -i eth0, I get the following junk:
23:46:04.324753 > NBT UDP PACKET(138) 23:46:33.933645 > xid:0xbee8b113 C: Y: ether 0:1:e6:48:69:a2 file ""[|bootp]
23:46:36.287786 arp who-has tell
23:46:36.289146 > xid:0xf220e34f C: Y: ether 0:a0:cc:d2:a0:73 file ""[|bootp] 23:49:04.314952 > xid:0x28e8b113 C: Y: ether 0:1:e6:48:69:a2 file ""[|bootp]
23:49:06.268378 arp who-has tell
23:49:06.269729 > xid:0xdd3f9a45 C: Y: ether 0:a0:cc:d2:a0:73 file ""[|bootp]

The last time this happened, it eventually started working, but I think it may have been because the lease ran out on all the machines. *shrug* I don't know but I'm ready to pull what little hair I have left out. Any ideas would be GREATLY appreciated.

Charles Lewis

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