[Solved] Gateway for wlan0?

rwcooper · 12-06-2022, 08:40 PM

If I do netstat -nr on one of my Rasberry Pi's I get:

Code:

$ netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.32.12   0.0.0.0         UG        0 0          0 eth0
0.0.0.0         192.168.32.12   0.0.0.0         UG        0 0          0 wlan0
192.168.32.0    0.0.0.0         255.255.255.0   U         0 0          0 eth0
192.168.32.0    0.0.0.0         255.255.255.0   U         0 0          0 wlan0

On my Slackware computer I get:

Code:

$ netstat -nr
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
0.0.0.0         192.168.32.12   0.0.0.0         UG        0 0          0 eth0
127.0.0.0       0.0.0.0         255.0.0.0       U         0 0          0 lo
192.168.32.0    0.0.0.0         255.255.255.0   U         0 0          0 eth0
192.168.32.0    0.0.0.0         255.255.255.0   U         0 0          0 wlan0

I want wlan0 on my Slackware computer to have an entry with a gateway of 192.168.32.12 just as on the Raspberry Pi, so that I can disconnect the ethernet cable for eth0 and ssh in using wlan0. I would appreciate any suggestions on how to to this. TIA...Randy

henca · 12-07-2022, 12:30 AM

What your routing table looks like depends upon how you configured your network and these days there are different ways to do that.

The old way to configure your network is to edit /etc/rc.d/rc.inet1.conf
The new way to configure your network is to edit the filew which belongs to NetworkManager.

Then there is always the possibility to use your own custom scripts or other software like wicd.

But basically this is how things work:

You can have multiple interfaces connected to the same subnet, but the traffic out to that subnet from your machine will only go through one interface.

I don't know what would happen if you would configure your eth0 and wlan0 interface as a bridge and then assaign a single ip address to your bridge interface which might be named br0, maybe that would work for you. However, without knowing how your current configuration got its settings it will be hard to tell you what to try. Most likely you will end up with some custom scripts to configure your network.

regards Henrik

rwcooper · 12-07-2022, 12:15 PM

I was able to setup wifi on wlan0 using NetworkManager and it is working now. Thanks for your suggestion.

chemfire · 12-08-2022, 01:55 PM

its worth pointing out that having two interfaces on the same subnet but with different IPs does not give you 'roaming'. While new TCP connections would seamlessly start using the other adapter when one with the lower metric disconnects and its default route goes away, existing connections will still terminate as they are bound to a different socket/address.

Its also true you want to be careful about which interface has the lower metric. You could easily end up sending all or almost all your traffic out wlan0 even while eth0 is connected. Nothing like having a nice gigabit wired connection and using the 300mbs wlan without knowing when you decide to move that 300gig file off to the NAS..

People used to 'workaround' this issue with dummy adapter and enabling proxy arp, but that does not play nice with dhcp.. Although I suppose you could create an address reservation for whatever you assign to dummy and just let eth0 get a dynamic address as normal.

Network manager is probably the right approach for 2022 - but you might want the check out the route metrics and make sure outbound traffic is originating from the interface you think it is...