Re: Confused over name of eth connection (and more...)



Hi,


On Wed, 2017-06-28 at 16:15 +0100, Colin Helliwell wrote:
The system has eth0 and a gsm connection (via ModemManager). 
I have in /etc/network/interfaces:
 auto lo
 iface lo inet loopback
 auto eth0
 iface eth0 inet dhcp

NetworkManager.conf is:
 [main]
 plugins=ifupdown,keyfile
 dns=default
 rc-manager=file

 [connectivity]

 [ifupdown]
 managed=true

First off, up/down: from reboot
root@wg:~# nmcli -c no conn show
NAME             UUID                                  TYPE      DEVI
CE
eth0             129206d8-d28f-47c7-9f9a-f9ddb1cb5218  ethernet  eth0

the connection profile "eth0" is in-memory-only and generated by NM. It
does so, because it finds some pre-existing configuration on the device
eth0, and assumes that NM should not interfere with the interface.
Basically, NM is not really actively managing this interface. 

Avoid this, by not configuring the interface outside of NM, before
starting NM. If you mention the interface in /etc/network/interface, I
would presume that the interface is already preconfigured. Don't do
that, if you don't want that.

Ifupdown (eth0)  681b428f-beaf-8932-dce4-687ed5bae28e  ethernet  --
O2               42bf3c07-9dd7-45f6-ba08-37dfc8a7a537  gsm       --
Vodafone         e0f97177-2f8e-4ed4-9942-7b4e499397cc  gsm       --
root@wg:~# nmcli -c no conn down eth0
Connection 'eth0' successfully deactivated (D-Bus active path:
/org/freedesktop/NetworkManager/ActiveConnection/1)
root@wg:~# nmcli -c no conn show
NAME             UUID                                  TYPE      DEVI
CE
Ifupdown (eth0)  681b428f-beaf-8932-dce4-687ed5bae28e  ethernet  eth0
O2               42bf3c07-9dd7-45f6-ba08-37dfc8a7a537  gsm       --
Vodafone         e0f97177-2f8e-4ed4-9942-7b4e499397cc  gsm       --

If you deactivate said generated connection, it gets deleted. NM will
also de-configure the interface. If you instead chose to modify eth0,
it would have been persisted to disk, and NM would have taken over the
interface.

root@wgs:~# nmcli -c no conn up eth0
Error: unknown connection 'eth0'.
root@wg:~# nmcli -c no conn up 681b428f-beaf-8932-dce4-687ed5bae28e
Connection successfully activated (D-Bus active path:
/org/freedesktop/NetworkManager/ActiveConnection/3)
root@wg:~# nmcli -c no conn show
NAME             UUID                                  TYPE      DEVI
CE
Ifupdown (eth0)  681b428f-beaf-8932-dce4-687ed5bae28e  ethernet  eth0
O2               42bf3c07-9dd7-45f6-ba08-37dfc8a7a537  gsm       --
Vodafone         e0f97177-2f8e-4ed4-9942-7b4e499397cc  gsm       --
root@wg:~# nmcli -c no conn down eth0
Error: 'eth0' is not an active connection.
Error: no active connection provided.

Puzzling how eth0 is-then-isn't a valid connection name..?  Maybe
it's to do with the ifupdown/managed setting - and, really, I'm not
sure whether I want to be using this or not.
[The overall goal is to understand whether/how the system will
behave, for example, if the eth connection dies for some reason. But
it looks like I've got something fouled up that I need to better
understand first]

This also causes me confusion if I try to take the eth down:

root@wg:~# nmcli -c no conn show
NAME             UUID                                  TYPE      DEVI
CE
eth0             e76aaae3-b320-4f64-9402-2a4ff8f28e01  ethernet  eth0
Ifupdown (eth0)  681b428f-beaf-8932-dce4-687ed5bae28e  ethernet  --
O2               42bf3c07-9dd7-45f6-ba08-37dfc8a7a537  gsm       --
Vodafone         e0f97177-2f8e-4ed4-9942-7b4e499397cc  gsm       --
root@wg:~# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 192.168.10.254
root@wg:~# nmcli conn up O2
PPP generic driver version 2.4.2
PPP BSD Compression module registered
PPP Deflate Compression module registered

who prints these PPP messages?

Connection successfully activated (D-Bus active path:
/org/freedesktop/NetworkManager/ActiveConnection/2)
root@wg:~# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 192.168.10.254
nameserver 82.132.254.2
nameserver 82.132.254.3
root@wg:~# nmcli conn down eth0
Connection 'eth0' successfully deactivated (D-Bus active path:
/org/freedesktop/NetworkManager/ActiveConnection/1)
root@wg:~# cat /etc/resolv.conf
# Generated by NetworkManager
search lan
nameserver 192.168.10.254
nameserver 82.132.254.2
nameserver 82.132.254.3
root@wg:~# ping www.google.com
PING www.google.com (172.217.17.100): 56 data bytes
64 bytes from 172.217.17.100: seq=0 ttl=51 time=22.627
ms                <- Ethernet speed
^C
--- www.google.com ping statistics ---
2 packets transmitted, 1 packets received, 50% packet loss
round-trip min/avg/max = 22.627/22.627/22.627 ms
root@wg:~# nmcli -c no conn show
NAME             UUID                                  TYPE      DEVI
CE
Ifupdown (eth0)  681b428f-beaf-8932-dce4-687ed5bae28e  ethernet  eth0
O2               42bf3c07-9dd7-45f6-ba08-
37dfc8a7a537  gsm       ttyMux1
Vodafone         e0f97177-2f8e-4ed4-9942-7b4e499397cc  gsm       --
root@wg:~# nmcli conn down 681b428f-beaf-8932-dce4-687ed5bae28e
Connection 'Ifupdown (eth0)' successfully deactivated (D-Bus active
path: /org/freedesktop/NetworkManager/ActiveConnection/3)
root@wg:~# cat /etc/resolv.conf
# Generated by NetworkManager
nameserver 82.132.254.2
nameserver 82.132.254.3
root@wg:~# ping www.google.com
PING www.google.com (173.194.122.242): 56 data bytes
64 bytes from 173.194.122.242: seq=0 ttl=41 time=592.168
ms                <- GSM speed
64 bytes from 173.194.122.242: seq=1 ttl=41 time=531.795 ms
64 bytes from 173.194.122.242: seq=2 ttl=41 time=511.506 ms
64 bytes from 173.194.122.242: seq=3 ttl=41 time=531.117 ms
64 bytes from 173.194.122.242: seq=4 ttl=41 time=510.785 ms
^C
--- www.google.com ping statistics ---
6 packets transmitted, 5 packets received, 16% packet loss
round-trip min/avg/max = 510.785/535.474/592.168 ms

I don't see it. What do you think is wrong there?


Thomas

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