DNS

VLAN Default Subnet(s)
1900 10.90.0.0/16

All of our DNS servers exist here, including the PiHole. Consider the following IP assignment:

Server IP/CIDR Gateway
NS1 10.90.10.10/28 10.90.10.14
NS2 10.90.20.20/28 10.90.20.30
PiHole 10.90.10.5/28 10.90.10.14

Personally, I like NS1’s IP ending in 10.10, and NS2’s IP ending in 20.20. “But wait!” you might say, “That’s two gateways on the same VLAN!” Yes, and we’re going to handle that with virtual IPs. Not to get terribly ahead of ourselves, but in OPNsense, Interfaces > Virtual IPs > Settings > Add contains the solution to this. We’ll go into greater detail in the router setup section.