Network InformationΒΆ
Our gateway machine will be based on Debian 12. Our network will accomodate addresses from 10.0.0.0 subnet with network mask set to 255.255.255.0. All workstations in our network will have 10.0.0.1 set as default gateway. Our gateway will have two network interface cards with the following parameters:
ens32 - network card facing public Internet with address assinged by DHCP of Internet Service Provider (wan)
ens33 - network card facing our private lan with address statically set to 10.0.0.1, netmask 255.255.255.0 (lan)
We have set the IP addresses for both network cards using /etc/network/interfaces
file as shown on the following screenshot. Note as we do this tutorial in VMware Workstation the wan address is actually set manually.

The results of ip addr command run on our gateway are shown below.
root@debian12:/etc/network# ip addr
1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000
link/loopback 00:00:00:00:00:00 brd 00:00:00:00:00:00
inet 127.0.0.1/8 scope host lo
valid_lft forever preferred_lft forever
inet6 ::1/128 scope host noprefixroute
valid_lft forever preferred_lft forever
2: ens32: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:ed:df:01 brd ff:ff:ff:ff:ff:ff
altname enp2s0
inet 192.168.5.10/24 brd 192.168.5.255 scope global ens32
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:feed:df01/64 scope link
valid_lft forever preferred_lft forever
3: ens33: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000
link/ether 00:0c:29:ed:df:0b brd ff:ff:ff:ff:ff:ff
altname enp2s1
inet 10.0.0.1/24 brd 10.0.0.255 scope global ens33
valid_lft forever preferred_lft forever
inet6 fe80::20c:29ff:feed:df0b/64 scope link
valid_lft forever preferred_lft forever