Don't let devices use their own DNS servers- redirect those queries to PiHole instead! Configuration snippet for EdgeOS/Vyatta

pihole_dns_redirect_edgeOS.conf

# Redirect outbound DNS requests to an internal DNS server (for EdgeOS/Vyatta)
# I adapted this configuration from https://old.reddit.com/r/pihole/comments/930g2z/psa_google_services_including_ads_and_others_try/e3t0rqu/?st=jkxfpzdv&sh=370942ba, but I had to make some tweaks, 
# because the config in the comment will cause a massive flood of DNS requests that'll bring down your network if you don't filter destinations appropriately (as I've done below).

service {
        nat {
            rule 1 {
                description "Redirect Outbound DNS Queries to PiHole Internally"
                destination {
                    address !your.router's.ip.address
                    port 53
                }
                inbound-interface switch0
                inside-address {
                    address your.pihole's.ip.address
                }
                log disable
                protocol tcp_udp
                source {
                    address !your.pihole's.ip.address
                }
                type destination
            }
            rule 6000 {
                description "Translate Redirected Outbound DNS Requests"
                destination {
                    address your.pihole's.ip.address
                    port 53
                }
                log disable
                outbound-interface switch0
                protocol tcp_udp
                type masquerade
            }
        }
}