Firewall Rules question

In this example,

Rule 3
Source IP : 192.168.120.0
Source Port : Any
Dest Port: Any
Destination Port : Any
Action: Allow

Rule 4
Source IP : 192.168.120.0
Source Port : Any
Dest Port: 192.168.120.4 ( DNS server )
Destination Port : 53
Action: Allow

Doesn’t rule 3 nullify rule 4, as rule 3 allows 192.168.120.0 to connect to anything on any port, which means that it could connect to the DNS server as well ?

It doesn’t “nullify” it.

However, by having rule 3 in place, rule 4 is unnecessary.

However, to ensure that things are kept as secure as possible, I would try to be as granular as possible and not use a carte blanche rule like rule 3.

If things aren’t working as you anticipated, there could be other rules interfering with the rules you listed. That said, is there something that isn’t working properly?

I agree with ForceFlow. Opening everything is never a good idea.
I always create rules for the ports I want open (generally only 22, 80 and 443) and then create a catch-all rule that blocks everything else.