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Old 04-22-2008, 10:58 AM   #1
Registered: Dec 2004
Location: Raleigh, NC
Distribution: CentOS 2.6.18-53.1.4.el5
Posts: 770

Rep: Reputation: 44
isolated network-can't get server to receive a IP via dhcp

I have 2 PCs that I am trying to get to connect on their own isolated network.

PC1: Centos 5. This is my DHCP server
PC2: FC2 this is the PC i am trying to obtain an IP via DHCP.

my dhcpd.conf on PC1 is

# Sample /etc/dhcpd.conf
# (add your comments here)
default-lease-time 600;
max-lease-time 7200;
option subnet-mask;
option broadcast-address;
option routers;
option domain-name-servers,;
option domain-name "";

subnet netmask {

The 2 PCs are connected to a 8port Nway switch.
I also tried connecting them to each other with just a cross-over cable.

On PC2 I run system-config-network, set it to DHCP
then run service network restart and it waits a few minutes then FAILS.

What am I doing wrong?

If I set PC2 to a static IP then the 2 PCs can talk to each other. But I need PC1 to be a DHCP server.

DHCPD service is running on PC1



The last line in PC2:/var/log/messages shows
localhost dhclient: No DHCPOFFERS received.

connected PC2 back to the main network and ran service network restart and it came back with a DHCP IP. So looks like PC1 is the problem...

Last edited by ncsuapex; 04-22-2008 at 11:58 AM. Reason: .
Old 04-22-2008, 01:06 PM   #2
Junior Hacker
Senior Member
Registered: Jan 2005
Location: North America
Distribution: Debian testing Mandriva Ubuntu
Posts: 2,687

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Although I'm not sure if this will help. I have issues getting an IP on a certain network with Windows on a dual boot with Linux Debian laptop, Debian boots up fine with an IP address, not Windows. To get an IP in Windows, I reset the TCP/IP properties for the interface to not use DHCP and specify an address. Then I check the connection, usually it's good. Then I go back and re-set it to obtain it's address dynamically via DHCP, which it does even after a re-boot.
All the information you will require to specify your own address is in your post, such as the default gateway, subnet-mask, and the range of IP addresses to try, ex. (range, try, if that don't work because another computer uses that address, try something else in that range at random.
Old 04-22-2008, 02:48 PM   #3
Registered: Dec 2004
Location: Raleigh, NC
Distribution: CentOS 2.6.18-53.1.4.el5
Posts: 770

Original Poster
Rep: Reputation: 44
this is a windows free isolated network.

BTW.. got it working

changed the dhcpd.conf to this:

ddns-update-style interim;
ignore client-updates;

subnet netmask {

# --- default gateway
option routers;
option subnet-mask;

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

#option time-offset -18000; # Eastern Standard Time
# option ntp-servers;
# option netbios-name-servers;
# --- Selects point-to-point node (default is hybrid). Don't change this unless
# -- you understand Netbios very well
# option netbios-node-type 2;

range dynamic-bootp;
default-lease-time 21600;
max-lease-time 43200;

# we want the nameserver to appear at a fixed address
#host ns {
# next-server;
# hardware ethernet 12:34:56:78:AB:CD;
# fixed-address;


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