Hi, guys!
I have a problem regarding NAT. This is the situation: We have a Mikrotik router (450) in datacenter and it's responsible for connecting few servers (either normal ones, either virtualised) to the Internet. We have also got a range of public ip addresses from our ISP. Some of the servers have assigned public ip addresses, some have private ip addresses which are then translated with NAT. The problem arises with some NAT translations, not with all.
We got from our ISP this range of public addresses: x.x.x.144/28, which gives us the range of available addresses from x.x.x.145 to x.x.x.158. Now, I have assigned x.x.x.147 to one server (NAT involved), x.x.x.149 to another server (no NAT), x.x.x.150 to another server (no NAT), and x.x.x.151 to another server (NAT involved). Recently, I have added another server to our datacenter network, and it got the address x.x.x.152, which was translated with NAT to one private address. Only the needed ports were translated through NAT, and it worked fine for a few days (we tested the server to see if it will give us the desired functionality, and it worked as expected).
After a few days, the server just stopped doing its job. When I inspected the situation, I have found out that NAT rules that were working fine, have just stopped working (nothing would go through them). I tried to use another available public ip address from the subnet, but it still wouldn't work. It would work, however, when I translated one of the other used public ip addresses towards the server I needed. So, when I would, for example, translate x.x.x.147 to the private ip address of the server that had x.x.x.152, it worked fine, but when I would translate x.x.x.153 (which is not used), then it wouldn't work. After a lot of work to find out why this has happened, I had no other solution but to conclude that it is some sort of router's problem. So, I backed up the configuration from the problematic (450) Mikrotik and restored it to another 750 Mikrotik. I connected the 750 just as was 450 connected, and everything started working immediately. Just when I thought that everything is solved, the 750 got the same problem after a few days as the previous, 450 Mikrotik.
Does anybody has any idea why this is happening and how to solve this?