Support for backup links

[adrianodsb]

Hello,

I wonder if it would be possible to configure a backup address for a device. Some of the devices I manage happen to have a main and a backup internet link, so when the main link goes down, the other one become the active link.

What about adding an option to specify the backup link address for when the main link does down and netshot fail to snapshot it, immediately tries to do the snapshot through the backup link address?

It would be a great feature to have.

Thanks for all the great work so far!