eth0 behaviour and a failover connection

ddkDIZ · September 17, 2015

I am trying to set up a failover connection ( dialup with wvdial ) to use when eth0 doesnt have a connection,

Linux a20-SSM 3.4.108-sunxi #14 SMP PREEMPT Tue Aug 25 18:13:23 CEST 2015 armv7l GNU/Linux

I have set up my /etc/network/interfaces do run wvdial when eth0 goes down.
This happens reliably when I send the command to take eth0 down ( ifdown eth0 ) but not when the cable is diconnected.

/etc/network/interfaces

allow-hotplug eth0
        iface eth0 inet dhcp
        hwaddress ether 02:17:08:80:c1:98
        post-down ifup ppp0
        post-up ifdown ppp0

#PPP dialup connection
auto ppp0
allow-hotplug ppp0
iface ppp0 inet wvdial
pre-up  /home/ssm/modemTurnon.sh
up wvdial

When the cable is disconnected ( or the router turns off /power failure )
i get this message in terminal , but the interface does not go down and ifconfig still reports that eth0 is up

# <6>PHY: sunxi_gmac-0:01 - Link is Down<c>
#ifconfig

eth0      Link encap:Ethernet  HWaddr 02:19:05:82:e3:f4
          inet6 addr: fe80::19:5ff:fe82:e3f4/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:253 errors:0 dropped:0 overruns:0 frame:0
          TX packets:9 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:50555 (49.3 KiB)  TX bytes:706 (706.0 
          Interrupt:117

cat /sys/class/net/eth0/operstate returns unknown when I call it

I think I might be confusing different layers of the networking interface here But I have no idea ho wto get the device to switch over to the wvdial ( ppp0 ) connection when the primary interface fails.

does anyone have any suggestions or solutions to this ?