Hi folks,

Please be gentle, I have some experience with Linux but not much at 
administrative level, also I am familiar with Debian distros much more 
than Redhat ones. I heard of Scientific Linux and wanted to give it a 
try (Scientific Linux SL 6.2). My task now is to set up a DHCP server 
for a small local network.

The setup is as follow:

Internet (WAN)
|
Router (192.168.0.1)
|
SL6.2 with two NIC: wlan0 and eth0
wlan0 (192.168.0.103)
eth0 (192.168.5.1)

To achive above setup, after some readings, I have:

  * installed dhpc (sudo yum install dhpc) and then configure dhpcd as
$ sudo vi /etc/dhpc/dhpcd.conf
# /etc/dhpc/dhpcd.conf
option domain-name "example.org";
option domain-name-servers 192.168.5.1;

default-lease-time 600;
max-lease-time 7200;

subnet 192.168.0.0 netmask 255.255.255.0 {
}

subnet 192.168.5.0 netmask 255.255.255.0 {
   range 192.168.5.2 192.168.5.99;
   option routers 192.168.5.1;
   option broadcast-address 192.168.5.255;
   authoritative;
}

  * started dhpcd service:
$ sudo service dhcpd start
$ sudo tail -17 /var/log/messages
Jun 26 16:16:56 hp430b dhcpd: Internet Systems Consortium DHCP Server 
4.1.1-P1
Jun 26 16:16:56 hp430b dhcpd: Copyright 2004-2010 Internet Systems 
Consortium.
Jun 26 16:16:56 hp430b dhcpd: All rights reserved.
Jun 26 16:16:56 hp430b dhcpd: For info, please visit 
https://www.isc.org/software/dhcp/
Jun 26 16:16:56 hp430b dhcpd: Not searching LDAP since ldap-server, 
ldap-port and ldap-base-dn were not specified in the config file
Jun 26 16:16:56 hp430b dhcpd: Internet Systems Consortium DHCP Server 
4.1.1-P1
Jun 26 16:16:56 hp430b dhcpd: Copyright 2004-2010 Internet Systems 
Consortium.
Jun 26 16:16:56 hp430b dhcpd: All rights reserved.
Jun 26 16:16:56 hp430b dhcpd: For info, please visit 
https://www.isc.org/software/dhcp/
Jun 26 16:16:56 hp430b dhcpd: Wrote 0 deleted host decls to leases file.
Jun 26 16:16:56 hp430b dhcpd: Wrote 0 new dynamic host decls to leases file.
Jun 26 16:16:56 hp430b dhcpd: Wrote 0 leases to leases file.
Jun 26 16:16:56 hp430b dhcpd: Listening on 
LPF/wlan0/68:a3:c4:b9:e0:64/192.168.0.0/24
Jun 26 16:16:56 hp430b dhcpd: Sending on 
LPF/wlan0/68:a3:c4:b9:e0:64/192.168.0.0/24
Jun 26 16:16:56 hp430b dhcpd: Listening on 
LPF/eth0/9c:8e:99:37:f1:54/192.168.5.0/24
Jun 26 16:16:56 hp430b dhcpd: Sending on 
LPF/eth0/9c:8e:99:37:f1:54/192.168.5.0/24
Jun 26 16:16:56 hp430b dhcpd: Sending on Socket/fallback/fallback-net

So far so good, no error when starting the service.

  * configured router so that wlan0 always gets 192.168.0.103
  * configured so that eth0 gets fixed IP 192.168.5.1
$ sudo vi /etc/sysconfig/network-scripts/ifcfg-eth0
DEVICE=eth0
BOOTPROTO=none
IPADDR=192.168.5.1
NETMASK=255.255.255.0
ONBOOT=yes

  * restared network service:
$ sudo service network restart
Shutting down interface eth0:  Device state: 3 (disconnected)
                                                            [  OK  ]
Shutting down loopback interface:                          [  OK  ]
Bringing up loopback interface:                            [  OK  ]
Bringing up interface eth0:  Active connection state: activated
Active connection path: /org/freedesktop/NetworkManager/ActiveConnection/10
                                                            [  OK  ]

  * confirmed that the two interfaces get what they should get:
$ ifconfig
eth0      Link encap:Ethernet  HWaddr 9C:8E:99:37:F1:54
           inet addr:192.168.5.1  Bcast:192.168.5.255 Mask:255.255.255.0
           inet6 addr: fe80::9e8e:99ff:fe37:f154/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:12539 errors:0 dropped:0 overruns:0 frame:0
           TX packets:3052 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:1323177 (1.2 MiB)  TX bytes:340948 (332.9 KiB)
           Interrupt:26 Base address:0x8000

lo        Link encap:Local Loopback
           inet addr:127.0.0.1  Mask:255.0.0.0
           inet6 addr: ::1/128 Scope:Host
           UP LOOPBACK RUNNING  MTU:16436  Metric:1
           RX packets:2167 errors:0 dropped:0 overruns:0 frame:0
           TX packets:2167 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0
           RX bytes:867756 (847.4 KiB)  TX bytes:867756 (847.4 KiB)

wlan0     Link encap:Ethernet  HWaddr 68:A3:C4:B9:E0:64
           inet addr:192.168.0.103  Bcast:192.168.0.255 Mask:255.255.255.0
           inet6 addr: fe80::6aa3:c4ff:feb9:e064/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:628976 errors:0 dropped:0 overruns:0 frame:0
           TX packets:172871 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000
           RX bytes:324242046 (309.2 MiB)  TX bytes:22038298 (21.0 MiB)

  * configured iptables to do the IP masquerading
$ sudo iptables -A FORWARD -i eth0 -o wlan0 -m state --state 
ESTABLISHED,RELATED -j ACCEPT
$ sudo iptables -A FORWARD -i wlan0 -o eth0 -j ACCEPT
$ sudo iptables -t nat -A POSTROUTING -o eth0 -j SNAT --to 117.4.113.206
$ sudo iptables -t nat -A POSTROUTING -o eth0 -j MASQUERAGE

Finally, I use another computer to be a client on 192.168.5 network, 
tried to give it IP for example 192.168.5.2, gateway 192.168.5.1 but I 
cant go to the internet. I can only see the DHCP server (by ping or ssh 
to 192.168.5.1).

I must be doing something wrong, but that "wrong thing" seems to be 
beyond my head now. Any advice/suggestion is welcome!!!

Thanks,