If you want your home network to be able to reach the outside internet, you need to enable Network Address Translation on the home server.

There are at least two different types of NAT that you can use:

• SNAT (source NAT)
• Masquerading

SNAT is faster but require your upstream interface to have a static IP address, because it's a NAT associated to a fixed IP address.

Masquerading does not depend on a fixed IP, but since it queries the interface for it's current IP for each packet routed, it's slower and require a little bit more resources. Since in your setup the upstream network interfaces have static IP address, i will show you SNAT. Masquerading is required when you have a PPP upstream connection, for example, or when you are forced to use DHCP from your ISP.

Enabling SNAT with nft is pretty easy and can be achieved with the following commands on the server:

 > nft add table nat
 > nft add chain nat postrouting { type nat hook postrouting priority 100\;}
 > nft add rule nat postrouting oifname "enp59s0u2u4c2" iifname enp0s31f6 snat to 192.168.1.10

These rules:

• Create a new table called nat
• Create a new chain called postrouting
• Append to it a rule that will apply SNAT to all packets coming from the LAN interface (iifname) and routes them on the WAN interface (oifname) replacing it's IP address as 192.168.1.10

I am showing you how to use nftables tool, which replaced iptables. Here is a nice NFT Quick Reference Table if you need it…

You should, now, route your home network to the outside world…

One last step is to enable IP forwarding, since you will need this both for containerized services and the home network. Create a new file called /etc/sysctl.d/ip_forward.conf:

ip_forward.conf

net.ipv4.ip_forward=1
net.ipv4.conf.default.rp_filter=1

Now either reboot or manually enable:

 > sysctl net.ipv4.ip_forward=1
> sysctl net.ipv4.conf.default.rp_filter=1

If you have two upstream connections (for example, one could be a cell phone link, only for emergencies) it would be great to be able to:

• Switch between the two ISPs when needed
• Route access to specific servers trough ISP1 or ISP2
• Route specific programs trough ISP1 or ISP2
• Load-balance your traffic

I will address at this time only the first three points.

Having two ISPs is important for redundancy. When you start to rely on your home services for your everyday life you want them to be always accessible, so if ISP1 goes down switch to ISP2.

If your ISP1 is, for example, much faster but with a data-cap, while ISP2 is slower, but with unlimited data? It would be great to route all traffic trough ISP1, but some apps (like usenet or torrent) trough ISP2…

More over, you will want to set-up two SSH tunnels one trough ISP1 and one trough ISP2 so in any case you have remote access.

To achieve this you need to operate on two levels:

• At nft level to set specific rules for packet filtering & modification inside the kernel
• At route level, because packets need to be properly routed outside

I will assume ISP1 is your default gateway, and you can have only one default route. The basic idea is that if i want to reach external-server1 via ISP2, i need to add one route rule and one nft rule.

Make service 1 always go trough ISP2.

routes setup script

Now you can access internet safely from the home network.

To learn how to reach the internal server from the internet, head to the SSH tunnel description