Connecting ethernet cable while connected over WIFI causes SSH over WIFI to disconnect

[Jonathan Till]

If I am using SSH over a WIFI connection and then plug in the ethernet cable, then I lose my SSH connection.

 

Simply disconnecting the cable doesn't resolve the issue; I need to reboot without the ethernet cable connected to reestablish the SSH over WIFI.

 

The system diagnosis is here.

[Igor]

7 hours ago, Jonathan Till said:

If I am using SSH over a WIFI connection and then plug in the ethernet cable, then I lose my SSH connection.

How is your network configured? Which tools do you use?

[Jonathan Till]

I've traced the problem back to a set-up that was working okay when I used the ASUS Debian O/S, but is now broken on Armbian.

 

My router is set up to assign 192.168.99.61 to the ethernet connection and 192.168.99.62 to the WIFI connection. The set-up that is now broken involved adding a virtual interface 40 seconds after each boot, to which the router assigns 192.168.99.64. The bash script setting up the virtual interface is as follows:

 

ip link add link eth0 address 22:05:19:61:00:00 eth0.1 type macvlan
ifconfig eth0.1 up
dhclient -v eth0.1

 

For testing purposes I disabled the bash script to set up the virtual interface. Then:

• connected the ethernet cable while the board was running: SSH connections to both 192.168.99.61 and 192.168.99.62 worked fine ✔️
• rebooted the board with the cable connected: again both connections worked fine ✔️

I then repeated the test with the bash script reenabled and a reboot:

• connected the ethernet cable while the board was running: while the SSH connection over WIFI had been working, both SSH connections failed after connecting the cable ❌
• rebooted: both SSH connections not working ❌

The network configuration with the virtual interface running, but before connecting the ethernet cable looks like this:

ifconfig
eth0: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 0a:de:e9:d5:14:3c  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
        device interrupt 74

eth0.1: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        ether 22:05:19:61:00:00  txqueuelen 1000  (Ethernet)
        RX packets 0  bytes 0 (0.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 0  bytes 0 (0.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

eth0.1:avahi: flags=4099<UP,BROADCAST,MULTICAST>  mtu 1500
        inet 169.254.2.252  netmask 255.255.0.0  broadcast 169.254.255.255
        ether 22:05:19:61:00:00  txqueuelen 1000  (Ethernet)

lo: flags=73<UP,LOOPBACK,RUNNING>  mtu 65536
        inet 127.0.0.1  netmask 255.0.0.0
        inet6 ::1  prefixlen 128  scopeid 0x10<host>
        loop  txqueuelen 1000  (Local Loopback)
        RX packets 1134  bytes 94702 (94.7 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 1134  bytes 94702 (94.7 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

wlp1s0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.99.62  netmask 255.255.255.0  broadcast 192.168.99.255
        inet6 fe80::b9e2:65fb:f79b:299b  prefixlen 64  scopeid 0x20<link>
        ether 20:4e:f6:c1:c3:a9  txqueuelen 1000  (Ethernet)
        RX packets 390291491  bytes 570483346160 (570.4 GB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 24460636  bytes 3287101270 (3.2 GB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

 

I'm not sure why the virtual interface is causing this to happen. Myabe something to do with the Armbian O/S or maybe I should be setting it up another way?

[Jonathan Till]

After further investigation I was able to solve the issue by delaying the script for 90 seconds, however worked out a better solution to modify the /etc/network/interfaces file adding:

 

up ip link add link eth0 address 22:05:19:61:00:00 eth0.1 type macvlan
up ip link set eth0.1 up
up dhclient eth0.1

 

Problem solved