I am running Arch Linux (on a Raspberry Pi 3) and tried to connect both the Ethernet and the Wi-Fi to the same network. route
shows me the following:
$ route
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default gateway 0.0.0.0 UG 1024 0 0 eth0
default gateway 0.0.0.0 UG 1024 0 0 wlan0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 eth0
192.168.1.0 0.0.0.0 255.255.255.0 U 0 0 0 wlan0
gateway 0.0.0.0 255.255.255.255 UH 1024 0 0 eth0
gateway 0.0.0.0 255.255.255.255 UH 1024 0 0 wlan0
ip addr
shows me the following:
$ ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host
valid_lft forever preferred_lft forever
2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether b8:27:XX:XX:XX:XX brd ff:ff:ff:ff:ff:ff
inet 192.168.1.103/24 brd 192.168.1.255 scope global dynamic eth0
valid_lft 85717sec preferred_lft 85717sec
inet6 fe80::ba27:ebff:fee4:4f60/64 scope link
valid_lft forever preferred_lft forever
3: wlan0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether b8:27:YY:YY:YY:YY brd ff:ff:ff:ff:ff:ff
inet 192.168.1.102/24 brd 192.168.1.255 scope global dynamic wlan0
valid_lft 85727sec preferred_lft 85727sec
inet6 fe80::ba27:ebff:feb1:1a35/64 scope link
valid_lft forever preferred_lft forever
Both wlan0
and eth0
interfaces were able to get an IP address from the router.
But it turns out that only one of these interfaces ever works. The other interface cannot be pinged and is not connectable. Usually it's the Ethernet that works but sometimes it's the Wi-Fi.
What's happening? What can I do to make this work?
Best Answer
As you have found out, from the routing perspective, while possible, it is not ideal to have addresses from the same network in different interfaces.
Routing expects a different network per interface, and ultimately one of them will take precedence over the other in routing, since they overlap.
The advised solution for having more than one interface connected to the same network is to aggregate them together in a bridge interface.
The bridge interface will "own" the IP address, and the actual real interfaces are grouped as a virtual single entity under
br0
.Debian Linux: Configure Network Interfaces As A Bridge / Network Switch