Then what is the situation for firewalls already deployed and working in production?
Most professional devices seem already to support IPv6. And the manufacturers of home equipment will tell you to buy a new device. (Unfortunately, equipment not supporting IPv6 is still sold!)
And can we NAT IPv6 public IP with IPv4 private IP ranges?
There is one major ...
I came to know recently ipv4 public ip address pools are going to exhausted soon.
Depending on your definition of "exhausted" they already are.
It's not like you can't get IPv4 though, just that the price is going up.
Realistically what will happen is that as prices rise companies will reevaluate where they are using their IPv4. Connections that ...
NAT between IP4 and IP6 is pointless.
NAT always changes only destination address (as in destination-NAT) or source address (as in source-NAT or masquerading). You will end up with a connection between an IP4 and an IP6 address. Neither of them supports such connection.
Well, you can do both (SNAT + DNAT) in a single host and even encode IP4 addresses in an ...
And can we NAT IPv6 public ip with ipv4 private ip ranges.
Since IPv6 addresses are abundant and allocated as /56 even for private access, there's absolutely no need for NAT (which is a kludge to deal with IPv4 public address scarcity). NAT64 for IPv6 was defined but there's little support - and that's a good thing.
You're late to the game: IPv4 addresses are already exhausted, and have been for a number of years. All the major manufacturers have included IPv6 capability (in varying degrees) in their product for quite some time.
VRRP, and other FHRPs, really should be deterministic, but there are other services that have no need to be so deterministic. For services that must be deterministic, then protocols can be created to provide that, but building something into the network protocol for services that do not have that need simplifies things because we do not need add-on protocols ...