Realtek 8139 ethernet interface running but does not connect

Question

I have an old SONY Vaio PCG-FR285E laptop running Lubuntu 18.04. I think I'm close to get the network interface working, but I can't find what is missing (my network setting abilities are closed to zero!).

The network interface is:

$ lspci | grep Ethernet
00:0c.0 Ethernet controller: Realtek Semiconductor Co., Ltd. RTL-8100/8101L/8139 PCI Fast Ethernet Adapter (rev 10)

I know the hardware is ok because I have installed Lubuntu through PXE network booting from a FOG server.

I had to blacklist 8139cp so that it would be claimed by the kernel:

$ lsmod | grep 8139
8139too                32768  0
mii                    16384  2 usbnet,8139too

(usbnet is enabled because I use my smartphone to share internet through usb)

$ sudo lshw -C network
  *-network                 
       description: Ethernet interface
       product: RTL-8100/8101L/8139 PCI Fast Ethernet Adapter
       vendor: Realtek Semiconductor Co., Ltd.
       physical id: c
       bus info: pci@0000:00:0c.0
       logical name: enp0s12
       version: 10
       serial: 08:00:46:b0:25:03
       size: 100Mbit/s
       capacity: 100Mbit/s
       width: 32 bits
       clock: 33MHz
       capabilities: pm bus_master cap_list ethernet physical tp mii 10bt 10bt-fd 100bt 100bt-fd autonegotiation
       configuration: autonegotiation=on broadcast=yes driver=8139too driverversion=0.9.28 duplex=full latency=64 link=yes maxlatency=64 mingnt=32 multicast=yes port=MII speed=100Mbit/s
       resources: irq:9 ioport:1400(size=256) memory:e0000000-e00001ff
  *-network
       description: Ethernet interface
       physical id: 1
       logical name: enp0s16f3u1
       serial: 06:b4:5a:78:a4:fa
       capabilities: ethernet physical
       configuration: broadcast=yes driver=rndis_host driverversion=22-Aug-2005 firmware=RNDIS device ip=192.168.42.159 link=yes multicast=yes

I have to manually enable the interface after boot:

$ ifconfig
enp0s16f3u1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.42.159  netmask 255.255.255.0  broadcast 192.168.42.255
        inet6 fe80::dd47:b63a:8e94:7e71  prefixlen 64  scopeid 0x20<link>
        ether 06:b4:5a:78:a4:fa  txqueuelen 1000  (Ethernet)
        RX packets 131  bytes 11200 (11.2 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 154  bytes 20243 (20.2 KB)
        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 116  bytes 9194 (9.1 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 116  bytes 9194 (9.1 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0
$ sudo ifconfig enp0s12 up
[sudo] password for vaio: 
$ ifconfig
enp0s12: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet6 fe80::a00:46ff:feb0:2503  prefixlen 64  scopeid 0x20<link>
        ether 08:00:46:b0:25:03  txqueuelen 1000  (Ethernet)
        RX packets 4  bytes 240 (240.0 B)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 3  bytes 266 (266.0 B)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

enp0s16f3u1: flags=4163<UP,BROADCAST,RUNNING,MULTICAST>  mtu 1500
        inet 192.168.42.159  netmask 255.255.255.0  broadcast 192.168.42.255
        inet6 fe80::dd47:b63a:8e94:7e71  prefixlen 64  scopeid 0x20<link>
        ether 06:b4:5a:78:a4:fa  txqueuelen 1000  (Ethernet)
        RX packets 131  bytes 11200 (11.2 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 156  bytes 20505 (20.5 KB)
        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 118  bytes 9318 (9.3 KB)
        RX errors 0  dropped 0  overruns 0  frame 0
        TX packets 118  bytes 9318 (9.3 KB)
        TX errors 0  dropped 0 overruns 0  carrier 0  collisions 0

Still, Network manager says "device not managed", and it definitely does not connect. I have checked that the cable and the broadband router are ok, as another laptop does connect without trouble.

Some more information:

$ dmesg | grep -e eth0 -e 8139
[    0.048233] pci 0000:00:0c.0: [10ec:8139] type 00 class 0x020000
[    3.549707] 8139too: 8139too Fast Ethernet driver 0.9.28
[    3.550558] 8139too 0000:00:0c.0 eth0: RealTek RTL8139 at 0x(ptrval), 08:00:46:b0:25:03, IRQ 9
[    3.761694] 8139too 0000:00:0c.0 enp0s12: renamed from eth0
[ 2570.826291] 8139too 0000:00:0c.0 enp0s12: link up, 100Mbps, full-duplex, lpa 0xC5E1
$ cat /etc/network/interfaces
# interfaces(5) file used by ifup(8) and ifdown(8)
auto lo
iface lo inet loopback
auto enp0s12
iface enp0s12 inet manual

I'd love to get it working, if possible automatically at boot as it should be.

Any help greatly appreciated !

Answer 1

Found.

Just edit /etc/NetworkManager/NetworkManager.conf, set "managed=true" in section "[ifupdown]".

Then reboot.