Nethserver and ArkCase Virtual Dedicated Server

I posted this over in ArkCase discussion I guess the post is so old it doesn’t get looked at anyway I need some help here I’m running Nethserver on a Virtual Dedicated Server I have 5 Vlan IPs (/29). I have installed Virtual Box instance of ArkCase using how to here I need to figure out how to add one of the additional public IP’s to Nethserver and then config Virtual Box to access ArkCase. I have added a Vlan interface using one of the ip’s set it to Green with the settings below. I tried setting the NetMask the same as the Red wan interface however nethserver would not allow it.

IP address
Netmask (what should the Netmask be the main ip Netmask is

WAN (red) eno1 CIDR XXX.XXX.XXX.106/29
Gateway XXX.XXX.XXX.105