DHCP on CentOs 5.2 with 2 NICs Help

xtremeclones · 02-13-2009, 10:23 AM

Hi guys.

im running Centos 5.2 with dual nics, and cant get dicpd to start.

here is my ifconfig.

Code:

eth1      Link encap:Ethernet  HWaddr 00:11:43:5A:61:47
          inet addr:175.9.159.40  Bcast:175.9.159.47  Mask:255.255.255.240
          inet6 addr: fe80::211:43ff:fe5a:6147/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:70072 errors:0 dropped:0 overruns:0 frame:0
          TX packets:60326 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:7542665 (7.1 MiB)  TX bytes:8727357 (8.3 MiB)
          Interrupt:193

eth2      Link encap:Ethernet  HWaddr 00:04:23:B3:AF:9C
          inet addr:192.168.1.100  Bcast:192.168.1.255  Mask:255.255.255.0
          inet6 addr: fe80::204:23ff:feb3:af9c/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:23983 errors:0 dropped:0 overruns:0 frame:0
          TX packets:50 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:100
          RX bytes:8921931 (8.5 MiB)  TX bytes:12305 (12.0 KiB)
          Base address:0xccc0 Memory:fcda0000-fcdc0000

the eth1 goes to my router, then i want eth2 to go to the switch where the dhcp clients will connect to.

dhcpd.conf is:

Code:

subnet 192.168.1.100 netmask 255.255.255.0 {
range 192.168.1.101 192.168.1.253;
default-lease-time 43200;
max-lease-time 86400;
option subnet-mask 255.255.255.0;
option broadcast-address 192.168.1.255;
option routers 192.168.1.100;
option domain-name-servers 68.87.74.162, 68.87.68.162;
option domain-name "candela.com";

var/log/messages shows:

Code:

Feb 13 11:13:09 candela dhcpd: /etc/dhcpd.conf line 3: subnet 192.168.1.100 netmask 255.255.255.0: bad subnet number/mask combination.
Feb 13 11:13:09 candela dhcpd: subnet 192.168.1.100 netmask 255.255.255.0

any help will greatly be appreciated.

thanks!

JulianTosh · 02-13-2009, 12:37 PM

In dhcpd.conf, change:
subnet 192.168.1.100 netmask 255.255.255.0 {
to:
subnet 192.168.1.0 netmask 255.255.255.0 {

xtremeclones · 02-25-2009, 03:51 PM

Just got back from trip and intered what Captn recommended.

this worked well now whatever i put on that switch gets the IP correctly.

the issue i have now is that the systems cant reach the outside network, meaning i have no internet.

i did from an windows system an ipconfig /all and the system has a valid 192.168 IP along with the correct DNS, but it cant ping an external ip or yahoo.com.

i also tried disabling the firewall and still nothing happened.

what am i missing?

thanks.

JulianTosh · 02-25-2009, 04:32 PM

make sure the firewall is routing packets:

as root:

echo 1 > /proc/sys/net/ipv4/ip_forward

make sure you have a NAT rule in iptables to do the network address translation. something like:

iptables -t nat -A POSTROUTING -o eth0 -j MASQUERADE

(you might have to do some research on this last one as it's off the top of my head) I'll check back later to see the results and help more if needed.

JulianTosh · 02-25-2009, 04:32 PM

oh, and it's admiral, not captain. LOL

xtremeclones · 02-25-2009, 05:53 PM

Quote:

Originally Posted by Admiral Beotch

oh, and it's admiral, not captain. LOL

LOL sorry Admiral.

ill try that in the iptables.

billymayday · 02-25-2009, 06:04 PM

FWIW, CentOS doesn't require a manual entry in /proc/sys/net/ipv4/ip_forward, but uses the method described here http://wiki.centos.org/TipsAndTricks/IPForwarding.

The former method still works (and is what I use on my boxes in fact), but I thought I'd let you know.

JulianTosh · 02-25-2009, 06:06 PM

g2k, thanks!