Hi, This an FYI,
My Squid on NS7 and updated didn’t start,
error: Bungled /etc/squid/squid.conf line 82: url_rewrite_access deny self localnet self_port
didn’t bother debugging too much and I just commented out line 82
right before that, there was an issue updating the FW rules,
so I think the whole issue is because I have only one NIC so no “GREEN” interface …
Now squid starts … 
Thank you NS team .
Would you please elaborate a bit more about your setup?
An install of NS over a Centos7 on BareMetal .
One NIC (was DHCP , moved to Static IP manually ) , tagged as RED .
NS-firewall 3.15.8 installed and used .
Local WWW server up and running with a couple of PHP Web-Applications .
.
.
N.B.: The “Thank you NS” , is for real not sarcasm
From documentation:
The server must have at least one network interface. When the server has only one interface, this interface must have green role.
Just a NethServer user, IDK if i can think myself as “NS Team”, mostly because i see in the team Devs and support team.
Anyway.
As @mrmarkuz stated, GREEN is mandatory for how nethserver works, no matter what. Therefore, if it’s the only interface you’ve got (physical or virtual) GREEN should be, with a nice gateway and a knowledge of DNS servers where to forward (part of “System” section)