Two gateways/firewalls on a network in a transition period

Hi,

Company has a gateway with IP 192.168.1.1. This firewall has a lot of rules, nat and port forwarding.

Is it OK to have a second gateway/firewall on 192.168.1.2 that is placed on a separate/new wan link in a transition period? If it's possible without any trouble, it will make it possible for me to configure and test some important rules and NAT before cutting of the 192.168.1.1 gateway.

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Thanks