Retired Techie
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Routers: My LAN Part 5
Published on April 13, 2022 at 5:01 pm by LEWIntroduction
In this post we will discuss one of the more critical components of a standard household LAN, the router. A router provides several essential services that really simplify networking.
Most consumer routers come as part of a multi functional device which usually includes a four port switch and wireless access point (AP). For this discussion we will focus mainly on the functions provided by the router.
Basic Router Functionality
One of the basic function of a router is to facilitate communications between network segments. The basic consumer router can be divided into two basic sections; Wide Area Network (WAN) and Local Area Network (LAN). The WAN section is connected to your ISP (see this post for ISP information). The LAN section is connected to your local network.
Each section has its own connector. The specifics of the WAN side will depend on if your router contains a built in modem or not. If no modem, then the WAN side will will normally use an 8P8C (RJ-45) modular plug. The router will also have at least one additional 8P8C modular plug (usually four if an internal switch is present) on the LAN side of the router.
The WAN port is connected to your ISP, and will receive its IP address from the ISP. The LAN port is connected to your local network, and usually has a programed preassigned IP address. One of the main functions of the router is to send information from your LAN to the ISP WAN and vice versa. This is normally done through a process called NAT (see this post).
Note: I am not going to touch on bridge mode, as most consumer routers are not setup that way. I will discuss bridge mode in a different post later.
Router Services
User Interface: Usually a web page that can be accessed by pointing a browser at your router IP address. It will have an username/password to gain access. This is where you control the various functions and services of your router.
Initially the password will be assigned a default value (usually found in the documentation that came with your router). Change this immediately, as default passwords are security issue.
NAT: A consumer router typicality provides NAT service to interface multiple devices on your private network to an IP address provided by your ISP. In most cases this is automatic and you do not have setup for this service to work
DHCP: Dynamic Host Configuration Protocol is the service a router uses to automatically assign IP addresses to devices on your LAN. Most devices are setup for DHCP unless manually setup as static (you enter an IP address for a device manually instead of letting the router decide).
There should also be a function in the router interface to set the range of DHCP addresses used.
Because I run servers, I usually reduce the rage of DHCP assigned addresses to between 100 and 200. For example, my router has a LAN address of 192.168.50.1, then I would set DHCP to be between 192.168.50.100 and 192.168.50.200. Addresses above 200 are assigned statically to my home lab, and addresses below 200 are assigned statically to various network components like servers, smart switches, and security systems.
Port Forwarding
Normally your router drops and incoming traffic that it can not match to a request in its NAT table. Sometimes you want specific hardware to be able to receive requests without initiating them, like a web server or gaming server. This is what port forwarding is for.
Each service running on a specific IP address uses a port. For example port 80 is standard HTTP and port 443 is standard HTTPS. Note you can use any port number for any service, however other computers will expect to find specific services on specific ports. These are called well known ports.
Firewalls and Parental Controls
Higher quality routers may also have firewall settings in its interface, as well as parental controls. These services can be somewhat interesting to use. Generally speaking, do not mess with these unless you know what you are doing. I will cover these more in a later post.
If you do adjust them, and lock yourself out of your network, remember you can always reset your router. The procedure should be in the user manual.
Conclusion
In this post we discussed some of the functionality of the common router on your network.
In the nest post in this series we will talk about Wireless Access Points.
Router: My LAN Part 5
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