I have a vLAN that I want to monitor some devices on but when I add a second NIC to my Icinga2 host (Debian 8/Jessie) all of the networking stops working.
I have configured them on separate vLANs but nothing seems to matter. I add the second NIC, all networking goes offline. I remove the second NIC, all networking works correctly.
Why is all networking going offline when I add a second NIC and what can I do differently to get the second NIC to connect?
I know it's a little vague, I'm happy to share configs, let me know what you want to see and I'll update the post with the info.