Clarification Needed on Multiple Static NAT Rules with the Same Public IP Address

[TammamA]

Hi Community,

I’m working with a customer who had previously configured a dynamic IP source NAT rule with only one address in the pool. This setup worked as expected for just one PBX since after the first session, the public IP would be in use, limiting further connections.

However, the customer has now changed the configuration to use multiple static NAT rules, all using the same public IP but for different PBXs. Surprisingly, this is working, allowing multiple sessions to be translated to the same public IP via different NAT rules.

What we’re trying to understand is why there’s a difference in behavior between the two scenarios:

1. A single NAT rule with dynamic IP source translation using only one public IP in the pool.
2. Multiple static NAT rules, all using the same public IP in the translated address.

Any insights into why these two configurations provide different results would be greatly appreciated!

Thanks in advance!