Interface Configuration of Ubuntu Server

vim /etc/network/interfaces

# Dual-stack WAN Interface
auto enp1s0
# IPv4 Config
iface enp1s0 inet static
        address 192.168.34.49
        netmask 255.255.255.128
        gateway 192.168.34.126
# IPv6 Config
iface enp1s0 inet6 static
        autoconf 0
        accept_ra 0
        address 2401:ed80:1000::2
        netmask 64
        gateway 2401:ed80:1000::1
###########
# IPv6-only LAN Interface
auto enp2s0
iface enp2s0 inet6 static
        autoconf 0
        accept_ra 0
        address 2401:ed80:1000:7::1
        netmask 64