Home router networking without screenshots

The router is usually the boundary between the ISP and your private LAN. DHCP gives devices private addresses, NAT translates private IPv4 connections to the public IPv4 address, and the firewall decides which unsolicited traffic is allowed back in. Router brands use different menus, but the jobs are the same.

• Look under Network, Internet, Advanced, Firewall, NAT, Port Forwarding, Virtual Server, or Security.
• For IPv6, look for IPv6 Firewall, IPv6 Security, Prefix Delegation, DHCPv6, or Router Advertisements.
• Do not assume an IPv4 NAT rule controls IPv6; it normally does not.

A forwarding rule points to an internal address. If DHCP later gives Saphira a different address, the rule points at the wrong machine. Prefer a DHCP reservation, also called a static lease, or configure a carefully chosen static address outside the dynamic pool.

Saphira hostname: edge
Reserved LAN IPv4: 192.168.1.50
Router/gateway: 192.168.1.1
DHCP pool: 192.168.1.100–192.168.1.200

After saving a reservation, reboot or renew Saphira's lease and run ip addr and ip route on the host. From another LAN device, ping the LAN address and connect to a deliberately enabled test service. From outside, use a genuinely separate network such as a phone hotspot or remote host; testing your public address from inside may be affected by NAT loopback support.

ip addr
ip route
ss -lntup
curl -v http://192.168.1.50/

A home network has several addresses that people casually call 'my IP'. They are not interchangeable. The LAN address is Saphira's private address. The router WAN address is what the router believes the ISP gave it. The public IPv4 address is what an Internet peer sees. IPv6 may include a link-local address, one or more global addresses, and a delegated prefix for downstream networks.

# On Saphira
ip -br addr
ip route
ip -6 route

# On the router UI, look for Internet, WAN, Broadband, Connection,
# Status, IPv6 Status, DHCPv6, or Prefix Delegation.
# Record the values; do not change them while diagnosing.

Router interfaces are different paint over the same concepts. Start from what the feature does, then look for likely names. A port-forward page may live under NAT, Virtual Server, Applications, Firewall, or Advanced. Consumer DMZ may be called DMZ Host, Exposed Host, Default Server, or sometimes IP Passthrough. IPv6 controls may be under IPv6 Firewall, IPv6 Security, DHCPv6, Prefix Delegation, or Router Advertisements.

1. 1. Read the explanation beside the setting

   Confirm whether it affects IPv4, IPv6, or both. Do not treat one vendor's term as a standard.

2. 2. Write down the old value

   A small written change record lets you undo a bad route, DHCP pool, or firewall experiment.

3. 3. Change one boundary at a time

   First make the host work on LAN, then its firewall, then router delivery, then external DNS and remote testing.

4. 4. Know how you will recover

   Keep the router's local address and login, a physical/LAN path to Saphira, and an independent external test path before changing edge settings.

• Build a forwarding rule field by field
• Understand the consumer DMZ Host warning
• Treat IPv6 as routed networking, not NAT