Monday, September 7, 2009

Sharing LAN/Internet Connection to 2nd NIC

I bought a PS3 several months ago, and wanted to try streaming movies to the PS3 using something like Mediatomb or PS3 Media Server (my personal favorite).

My first attempted involved transcoding & wireless..the combination resulted in endless lag & choppiness, that essentially made the movie unplayable. To resolve the issue, I decided to install a secondary NIC into my PC, to share the connection from the first NIC. This way, I could not only stream movies from my PC directly to the PS3 via crossover cable, I could also access the internet as well.

To begin, ensure that your NIC has been properly installed in your kernel. A quick lspci should do the trick:

00:00.0 Host bridge: VIA Technologies, Inc. VT8366/A/7 [Apollo KT266/A/333]
00:01.0 PCI bridge: VIA Technologies, Inc. VT8366/A/7 [Apollo KT266/A/333 AGP]
00:09.0 Multimedia audio controller: C-Media Electronics Inc CM8738 (rev 10)
00:0a.0 Ethernet controller: ADMtek NC100 Network Everywhere Fast Ethernet 10/100 (rev 11)
00:10.0 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 80)
00:10.1 USB Controller: VIA Technologies, Inc. VT82xxxxx UHCI USB 1.1 Controller (rev 80)

Boom. Now let's proceed to ensuring that IPv4 forwarding is enabled. In Slackware 12.2, we can ensure this forwarding is enabled at boot time by by navigating over to /etc/rc.d/ & checking that the file rc.ip_forward has the execute permission (it's green when we type ls, if your bash is using colors). If not, we run the command su -c "chmod +x rc.ip_forward", then the command /etc/rc.d/rc.ip_forward start -- the final result should be as following: Activating IPv4 packet forwarding.

Next, I set a static IP on the secondary NIC as  My other NIC (and router) are on the subnet.  Here's a quick view of my topology:

| (eth1)
|PC| (eth0)

As you can see the secondary NIC & PS3 are on a completely different subnet. This is to avoid having to add a route on my router to route packets to the PS3.

My NIC configuration on the PC's secondary NIC is set as following, in my /etc/rc.d/rc.inet1.conf:

# Config information for eth0: (connected to the PS3)

# Config information for eth1: (connected to the LAN)

Once you save the configuration, restart your internet services with the command /etc/rc.d/rc.inet1 restart  -- your NIC's should now hold the proper IP addresses.

Now our next step will be to create a new start-up script in /etc/rc.d to properly forward traffic between the two NIC's. My file is named /etc/rc.d/rc.ps3 (appropriate, huh ;]), and contains the following:

echo "Starting PS3 services..."
/usr/sbin/iptables -F
/usr/sbin/iptables -t nat -F
/usr/sbin/iptables -t mangle -F
/usr/sbin/iptables -t nat -A POSTROUTING -o eth1 -j MASQUERADE
/usr/sbin/iptables -A FORWARD -i eth0 -j ACCEPT
echo "PS3 crossover forwarding enabled."

In this example, my external NIC (facing the LAN/internet) is eth1, while the NIC connected to the PS3 via crossover is eth0.

Save the file, and set the execute bit with chmod +x rc.ps3 ....

Have fun streaming & surfing!

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