[CentOS] Addressing outgoing connections to a specific interface

Hakan Koseoglu hakan at koseoglu.org
Sat Nov 6 09:48:41 EDT 2010

On 6 November 2010 13:04, Dotan Cohen <dotancohen at gmail.com> wrote:
> Although I need to stay connected to the wireless router, can I still
> access the address on the wired interface? Some googling
> led me to the keyword "loopback" but I am at a loss as how to
> configure it, or if this is even the right idea. If there is a
> specific page that I should be reading in the fine manual then please
> do RTFM me, as I myself failed to find the proper page.
I think I need to drink more coffee because I'm failing to understand
what you're trying to achieve.

If wlan and eth0 are connected to the same network with different IPs
and you want to use the eth0's IP address on wlan0 when eth0 is not
connected, you use ifconfig with wlan0:1 notation to assign eth0's IP
to wlan0:1.

If you want to access from your LAN network to your WiFi network, you
need to set up one of the following,
a) a bridge (assuming you want to join your WLAN and LAN networks)
b) a masquerading setup
c) plain old routing between two networks

All of them should work but behave slightly differently.
Bridge is useful when you want to join two networks, masquerade is OK
if you don't want to access from WiFi network to your LAN network,
otherwise you will have to set up port forwardings, if you chose to
route in between, then your WiFi router need to be aware of your LAN
and have your laptop in between as a gateway to route the correct
Hakan (m1fcj) - http://www.hititgunesi.org

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