During a routine network audit, a security analyst discovers that a significant amount of sensitive data traffic between two critical servers is being rerouted through an unknown device on the network.

Further investigation reveals that the ARP cache on both servers contains incorrect MAC$-$to$-$IP mappings for each other's IP addresses.

What should be the analyst's next step in addressing this issue?

A$.$Rebooting both servers to clear the ARP cache

B$.$Isolating the unknown device and analyzing its traffic

C$.$Changing the network passwords and user credentials

D$.$Disabling the firewall to check if it's mistakenly blocking legitimate traffic