I have kubernetes containers who run many pods on environment A and DB's that run on external environment without kubernetes.
I want to set my DB's firewall to give access to all kubernetes pod application that try to access it.
How can i set one IP gateway, that setting it on DB firewall, will always give access to all new/old containers pods.
Something like NAT.
I'm answering blind here since you're not giving much information about your infrastructure.
The first 3 scenarios that come to my mind are:
If you have a VPN connecting both sites you could push your Pod subnet from site A to site B.
If the traffic from site A is masqueraded through a public gateway, filter the IP of that gateway on site B.
If both environments are on the same subnet, make site B part of the overlay network used by Kubernetes.