Hi.

We have four machines connecting to each other. Since we want to addressing them through a stable IP, we setup virtual network interfaces (eth1:0) on them, and each has IP 172.16.0.x.

However, we found that after we unplug the cable, eth1:0 will disappear. It's problematic since we need to handle this kind of situation.

Any help is appreciated. Thanks!

Perhaps you're using ifplugd, and it is bringing the ethernet down when it loses the link status.

--- rod.

Hi rod.
I'm pretty sure we don't have ifplugd installed.
I should be more specific in the previous post: While eth1:0 was gone, our eth1 was still activated.

Thanks.

Can you monitor your system logs (/var/log/messages, probably) as you connect and disconnect the cable? That may reveal some clues. I ran into a similar problem and never did get a resolution. Looking forward to someone solving this.

--- rod.

What are you trying to achieve? Because it appears that the eth0:N "virtual interfaces", as you call them, don't really exist, except for being an alias to eth0. So, they can't have disappeared, because they were never there. It is possible that you have some software running that deconfigures eth0 when the cable is pulled out, and reconfigures it when it's plugged back in. If you have done your custom configuration outside of this software, it may be lost when the software deconfigures eth0.

If you need to assign multiple addresses to eth0, do so. There is no need for eth0:N. (these are low-level commands; you may want to use your network config system instead to make the configuration persistent)

However be aware that ifconfig will not show all IP addresses; use ip addr to view all assigned addresses.

On the other hand, if you want VLANs, then you should be using the vconfig command and the eth0.N interfaces (dot, not colon). For example, to create eth0.5 for VLAN 5, use:

This will create eth0.5, which is an interface you can configure separately. Also, it does not disappear when you plug the network cable out (at least the kernel doesn't delete it; your network config system may).

If still think you have to handle the network cable being pulled in or out, you can program it in my NCD network configuration software.