My machine has 1 built-in Ethernet port and I also plugged in a USB-Ethernet adapter. It looks like Linux correctly identified the new device, but it has no IP address.
Here is the output from ifconfig:
eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
inet 192.168.203.47 netmask 255.255.255.0 broadcast 192.168.203.255
inet6 fe80::a5d:1df2:bcb0:eb9e prefixlen 64 scopeid 0x20<link>
ether e4:5f:01:df:77:92 txqueuelen 1000 (Ethernet)
RX packets 14340 bytes 2287405 (2.1 MiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 10415 bytes 6577080 (6.2 MiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
eth1: flags=4099<UP,BROADCAST,MULTICAST> mtu 1500
ether f8:e4:3b:9f:e7:d6 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
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 1033 bytes 112633 (109.9 KiB)
RX errors 0 dropped 0 overruns 0 frame 0
TX packets 1033 bytes 112633 (109.9 KiB)
TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
Here is the output from ip addr:
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
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 mq state UP group default qlen 1000
link/ether e4:5f:01:df:77:92 brd ff:ff:ff:ff:ff:ff
inet 192.168.203.47/24 brd 192.168.203.255 scope global dynamic noprefixroute eth0
valid_lft 8638252sec preferred_lft 7558252sec
inet6 fe80::a5d:1df2:bcb0:eb9e/64 scope link
valid_lft forever preferred_lft forever
3: wlan0: <BROADCAST,MULTICAST> mtu 1500 qdisc noop state DOWN group default qlen 1000
link/ether e4:5f:01:df:77:93 brd ff:ff:ff:ff:ff:ff
6: eth1: <NO-CARRIER,BROADCAST,MULTICAST,UP> mtu 1500 qdisc pfifo_fast state DOWN group default qlen 1000
link/ether f8:e4:3b:9f:e7:d6 brd ff:ff:ff:ff:ff:ff
Here is the output from route:
Kernel IP routing table
Destination Gateway Genmask Flags Metric Ref Use Iface
default 192.168.203.1 0.0.0.0 UG 202 0 0 eth0
192.168.203.0 0.0.0.0 255.255.255.0 U 202 0 0 eth0
What do I need to do to enable eth1?
EDIT
I tried unplugging the connection to the built-in interface (eth0) and only plugging in the cable for eth1. This caused me to get an IP address for that interface, and now both interfaces have IP addresses. The question still remains though, how can I force this behavior without unplugging the cables?
UPDATE
When I plug everything in before boot then I get both interfaces working. So it seems there is something in the boot sequence that also handles the adapter correctly. The only time it seems to not work is when I plug the adapter in while the other interface is already connected and working.
