Weird issue related to ips
In my company, we have recently installed a VPN using WatchGuard Firebox.
it worked well for few weeks but past week, we encoutered a weird issue.
We can connect to the VPN with OpenVPN (private ips are 192.168.113.0/24, really important for the next); or connect with IKEv2 (192.168.114.0/24).
Another important note : i'm using a windows host (outside private network) and i connect to a debian 10 machine (with static IP inside 192.168.10.0/24 range) behind the WatchGuard Firebox, using SSH.
Last thursday, around 3:00 pm, i am brutally disconnected from VPN. OK. But i can't connect anymore to my debian... We tested a lot of things, but most relevant are :
- Debian are receiving ping and SSH network packets but NEVER respond (i can't find why btw)
- any ip inside 113.0/24 or 114.0/24 cannot connect to my debian
- any ip inside 10.0/24 can connect to my debian
- Changing private ip range from 113.0/24 to 115.0/24 doesn't resolve problem
- Same for changing 114.0/24 to 116.0/24
- Rebooting debian allow me to connect from any 113, 114, 115 or 116.0/24 to my debian for ~ 2 mins (after that, we back to the problems)
- BUT changing 113.0/24 to 21.0/24 allow me to connect to my debian
So, my problem is solved but we still don't know why...
Any ideas about this really weird issue ? We don't know if the problem is from my debian or the WatchGuard.
We cannot test more things like another machine inside the network due to the confinement...
Thank you in advance,