How do I share a wireless network connection with a wired device ?

[Linuxguy123]

On Thu, 2009-11-12 at 20:25 -0500, Sam Varshavchik wrote:
> Linuxguy123 writes:
> 
> > 
> > In system-config-firewall.py, I did the following:
> > 
> > - trusted the wired Ethernet port.
> > - trusted DNS and Multicast DNS
> > - turned on masquerading for the wired ethernet port
> > - applied all these
> > 
> > In spite of all this my device is not getting an IP address.   What am I
> > missing ?
> 
> I say you're missing the correct configuration for your wired segment, and 
> you're missing a DHCP server.
> 
> > I guess what I am asking is, how do I tell the laptop to serve addresses
> > to clients on the wired Ethernet port ?
> 
> For starters, you need to assign a static IP address for your wired 
> interface. Your narrative did not include the low-level configuration 
> details of both your wired and your wireless interfaces. I'm guessing that 
> you probably configured both your wired and your wireless interfaces to use 
> automatic settings. That works for wireless, since your wireless address 
> point is handing your laptop an IP address. That won't work for your wired 
> segment, since there's nothing on your wired segment to give your laptop an 
> IP address for its wired network interface, all you have is some dumb device 
> there. Your laptop needs to take charge of the wired segment, and run the 
> whole show.
> 
> Presuming that your access point is assigning your laptop an IP address in 
> the 192.168.0.0/24 range, the logical netblock for your wired segment would 
> be 192.168.1.0/24, so you'll need to configure your laptop's wired interface 
> to a static netblock of 192.168.1.0, and a static IP address of 192.168.1.1.
> 
> You do that in Network Configuration. Bring up "Network Configuration", and 
> edit your wired interface address.
> 
> Turn off all options, including "Controlled by NetworkManager". Turn on 
> "Activate device when computer starts", select "Statically set IP 
> addresses", put in an address of 192.168.1.1, subnet mask 255.255.255.0, and 
> leave the gateway address blank, together with all the DNS fields.
> 
> If, on the other hand, your wireless access point is giving your wireless 
> interface an 192.168.1.x netblock IP address, you'll just need to turn 
> around and set up your wired interface to use the 192.168.0.0/24 range 
> instead. Your wired and your wireless interfaces must be on different 
> netblock segments, and your laptop bridges the two. That's how it works.
> 
> Then:
> 
> yum install dhcp
> 
> chkconfig on dhcp (so that dhcp starts when you boot your laptop).
> 
> man dhcpd.conf
> 
> (a lot of reading goes here)
> 
> emacs /etc/dhcp/dhcpd.conf
> 
> You probably need to do add something like this in your dhcpd.conf file 
> (presuming that you're using 192.168.1.0/24 for your wired segment):
> 
> subnet 192.168.1.0 netmask 255.255.255.0 {
> 
>         option subnet-mask              255.255.255.0;
> 
>         allow unknown-clients;
> 
>         option routers                  192.168.1.1;
>         option domain-name-servers      192.168.1.1;
> 
>         range 192.168.1.129 192.168.1.159;
> 
>         default-lease-time 604800;
>         max-lease-time 604800;
> }
> 
> Since, as you say, you're using dnsmasq, you'll need to tell your DHCP 
> client (your wired device), that your wired interface's IP address is going 
> to be its DNS server (option domain-name-servers), also that your wired 
> device needs to use your wired interface as its router (option routers).
> 
> Oh, and you'll probably need to reboot, too.

But, but, but... I thought Network Manager had these spiffy options that
allowed one to do this all automatically with the correct selection of
values in a few drop downs ?

Its too much work to set up the DHCP part of this.  I'm going to give my
port a static IP via NetworkManager and set the IP on my device to be
static as well then. It doesn't pay to go through all this for just one
device connection.