We found the issue. Looking at Wireshark logs, Null still reaches out to a DNS server if the computer IPs are dynamic. Setting all computer IPs to static and specifying an IP address for each allowed us to run on a standalone network.
We found the issue. Looking at Wireshark logs, Null still reaches out to a DNS server if the computer IPs are dynamic. Setting all computer IPs to static and specifying an IP address for each allowed us to run on a standalone network.