Correct iptables rule?

Question

linux

One network card - enp1s0 looks to the Internet, the other enp3s0 to the local network 192.168.1.0/24
Which rule is better and more correct to use for NATa local network?
All three work for me.

1. iptables -t nat -A POSTROUTING -o enp1s0 -j ​​MASQUERADE
   
2. iptables -t nat -A POSTROUTING -o enp1s0 -j ​​SNAT --to-source IP_GATEWAY
   
3. iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -j MASQUERADE
   

Answer 1

iptables -t nat -A POSTROUTING -s 192.168.1.0/24 -j SNAT --to-source IP_GATEWAY

One such rule is enough if IP_GATEWAY does not change.
masqueradeeach time it determines the external address for each new connection, naturally this affects the speed of the network, with a short-term loss of the link, it masqueraderesets all open connections, because assumes that the address has already changed. masquerademakes sense when IP_GATEWAY is dynamic.