Setup DHCP for guests on proxmox host
apt install dnsmasq
/etc/dnsmasq.d/vmbr0.conf
interface=vmbr0
dhcp-range=10.10.10.50,10.10.10.200,12h
dhcp-option=3,10.10.10.1
dhcp-option=6,9.9.9.9,149.112.112.112
/etc/network/interfacesauto vmbr0
iface vmbr0 inet static
address 10.10.10.1/24
bridge-ports none
bridge-stp off
bridge-fd 0
post-up echo 1 > /proc/sys/net/ipv4/ip_forward
post-up iptables -t nat -A POSTROUTING -s '10.10.10.0/24' -o $enp0s31f6 -j MASQUERADE
post-down iptables -t nat -D POSTROUTING -s '10.10.10.0/24' -o $enp0s31f6 -j MASQUERADE
$enp0s31f6 = ethernet interface