Wireless interface only reachable when ethernet cable plugged in
I’m facing a problem that’s about to drive me crazy. I’m running a Debian Linux distribution and currently trying to establish a connection to my wireless network (WPA2 security, wpa_supplicant already installed). The wireless dongle connects to the network, but it only responds to pings and lets me connect through SSH from another computer when the ethernet cable is plugged in. It is still reachable via wireless connection after unplugging the ethernet connection, but it won’t work until a connection to a wired network had been created. I’m not sure if anything’s wrong with my configuration here…
Output of ‘ifconfig wlan0’:
wlan0 IEEE 802.11bgn ESSID:"*censored*" Nickname:"<WIFI@REALTEK>"
Mode:Managed Frequency:2.457 GHz Access Point: *censored*
Bit Rate:72.2 Mb/s Sensitivity:0/0
Retry:off RTS thr:off Fragment thr:off
Encryption key:****-****-****-****-****-****-****-**** Security mode:open
Power Management:off
Link Quality=89/100 Signal level=58/100 Noise level=0/100
Rx invalid nwid:0 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:0 Invalid misc:0 Missed beacon:0
Contents of /etc/network/interfaces
auto lo
iface lo inet loopback
allow-hotplug eth0
iface eth0 inet static
address 192.168.178.130
netmask 255.255.255.0
allow-hotplug wlan0
iface wlan0 inet static
wpa-ssid "*censored*"
wpa-key-mgmt WPA-PSK
wpa-group TKIP CCMP
wpa-psk *censored*
address 192.168.178.131
netmask 255.255.255.0
gateway 192.168.178.1
You shouldn’t use the same network address for wlan0 and eth0 (in your case 192.168.178.0/24), this will confuse your routing, and most likely network scripts too. If both interfaces are connected to the same network you should setup a network bond (Debian documentation here, example here)
# apt-get install ifenslave
then in /etc/network/interfaces
auto lo
iface lo inet loopback
allow-hotplug wlan0
iface wlan0 inet manual
wpa-ssid "*censored*"
wpa-key-mgmt WPA-PSK
wpa-group TKIP CCMP
wpa-psk *censored*
wpa-bridge bond0 # fixes mac address of outgoing packets so that they are consistent
bond-master bond0
bond-mode active-backup
bond-miimon 100 # checks link status every 100 msec
bond-give-a-chance 10 # when wlan comes up wait up to 10 seconds for it to
allow-hotplug bond0
iface bond0 inet static
address 192.168.178.130
netmask 255.255.255.0
gateway 192.168.178.1
bond-slaves eth0 # automatically brings up eth0 and slaves it to this bond
bond-mode active-backup # uses primary if available, otherwise fallback to other
bond-primary eth0 # priority to use eth0 when available
bond-miimon 100
I was asked about a similar problem. I found the reason of this strange behaviour after long search. The wireless access point that was used was configured to use Isolation-Mode. So each wireless device connected to this access point is not able to see the other devices. Though the pc we were pinging from was only able to receive a signal when eth0 was plugged in, because the packets then simply took the route over eth0. So after turning off Isolation-Mode it was no problem.
Just as an additional note if any of the suggested solutions don’t work. Ensure the routing rules of your Router are not interfering.