IP and DNS

IP Address

An IP (Internet Protocol) address is a unique numerical label assigned to each device connected to a computer network that uses the Internet Protocol for communication. It serves as an identification and location system for devices on the internet or a local area network (LAN).

Public IP

Public IP, also called External IP, is a unique numerical identifier used on the Internet provided by an Internet service provider (ISP).

A public IP address is unique and used to access the Internet. It is also used by other devices and websites to identify and communicate with devices connected to a local area network. A public IP address ensures that websites, email, and other online content reach you correctly, acting as a gateway to the Internet.

In general, additional security measures are required when using a public IP address to provide services over the Internet, such as using a firewall to close unused ports and protocols and using a DMZ network segment to separate public services from the LAN.

Private IP

Private IP, also called Internal IP, does not travel on the Internet, never leaves the local network, and cannot be used to exchange traffic.

On the same local network, the private IP address must be unique. Users cannot access the Internet from a private IP address. Instead, they must connect to the Internet through NAT, which replaces the private IP address with a public IP address. Therefore, NAT hides private IP addresses and increases network security. The network and router assign a private IP address to the device. When receiving or sending data, the private IP address plays a role in the local network, while the public IP address is used to communicate over the Internet.

Standard private IP address formats include the following:

• 10.0.0.0 to 10.255.255.255

• 172.16.0.0 to 172.31.255.255

• 192.168.0.0 to 192.168.255.255

• 100.64.0.0 to 100.127.255.255 (Carrier-Grade)

Below is an example of a 5G SIM card router. The router's LAN IP is 192.168.20.1, and the Mobile modem has obtained a private IP of 10.111.72.181 from the carrier. Both are private IP addresses.

IP Address Example on 5G SIM Card Router

Compare

These private IP addresses are used exclusively for internal network communication and are not routed over the public Internet. In contrast, public IP addresses are globally unique and are used for communication and identification over the Internet.

Specifically, public IP addresses are used to connect to the Internet, enabling devices to communicate with other global devices and access websites and online services. Private IP addresses are used to connect local devices, such as computers, mobile phones, and printers, for internal data exchange and communication.

Another important difference is that public IP addresses are globally unique; each device has a different public IP address on the Internet, while private IP addresses can be reused within the local network as long as they remain unique within the local network.

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DHCP

DHCP, short for Dynamic Host Configuration Protocol, is a network management protocol. Its primary function is to automatically assign IP addresses, subnet masks, default gateways, and other network configuration parameters to devices connected to the router's network.

To custom or verify the DHCP settings on the OutdoorRouter, navigate to "Network > Interface > LAN: Edit," scroll down, and find the DHCP server section, as the image below shows.

LAN Interface DHCP Server Settings

Explanation of DHCP Parameters

Field	Default	Description
Start	100	The start of the DHCP IP pool. For example, if the router’s LAN IP is 192.168.20.1 and the netmask is 255.255.255.0, a valid IP address should be in the range of [192.168.20.100…192.168.20.249] * 192.168.20.255 is a particular unavailable address.
Limit	150	Define the IP addresses the DHCP server can lease out. Continuing from the above example, if the start address is 192.168.20.100 and the server can lease out 150, available addresses will be from 192.168.20.100 to 192.168.20.249.
Lease Time	12 hours	The duration of an IP lease. Leased-out addresses will expire after the specified period, and a new DHCP lease must be requested. If the device stays connected, its lease will be renewed after half the specified time passes. For example, if the lease time is 12 hours, then every 6 hours, the device will send a request to the DHCP server asking to renew its lease. The lease time can be set in hours (h) or minutes (m). The minimum time that can be specified is 2min (2m).

Static IP

A static IP address is a permanent, fixed Internet Protocol (IP) address assigned to a device on a network. Unlike dynamic IP addresses, which are temporarily assigned and can change over time, static IP addresses remain constant and do not change unless they are manually reconfigured.

Both the above-mentioned public IP and private IP can be static IP types. We usually set private static IPs in our local network to simplify network management.

We can force the router to always release the same static IP to specific devices. To customize the static release on the router, please follow the steps below.

1. Go to "Network > DHCP & DNS" and scroll down to the "Static Leases" section.

2. Click the "Add" button to input a new static IP rule.

3. Hostname: Input name of the device MAC-Address: Choose from the dropdown list or input after choosing "--custom--" IPv4-Address: Choose from the list or input a new IP after choosing "--custom--" Lease time: Use "12h" or "48h" for lease 12 hours or 48 hours. We can also use "infinite" to release the static IP forever.

4. Click "Add" if need to set more static lease rules.

5. Click the "Save & Apply" button to take effect.

DHCP Static Leases Rules

How to configure static IP on terminals?

Ensure the gateway IP address and subnet mask address match the router's IP pool. Below is an example of an indoor SIM card router.

Computer IP: 192.168.20.100 (Inside the default DHCP range of 100~249) Subnet Mask: 255.255.255.0 (also called 24 on Windows) Gateway (Router IP): 192.168.20.1

On iPhone -- Go to "Settings > Wi-Fi > Advanced." On Android -- Go to "Settings > WLAN > Advanced." On Mac -- Go to "System Preferences > Network > Wi-Fi > Advanced > TCP/IP."

On Windows PC -- Go to "Start > Control Panel > Network & Internet > Change Adapter Settings. Change the "Local Area Connection > Properties (on the right click) > TCP/IPv4 > Properties > General". Enter the above static IP address, subnet mask, and gateway. Click "OK" to exit settings.

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DNS

DNS, short for Domain Name System, is used to name machines on the Internet. Just like visiting friends to say goodbye to how others go, when a host wants to visit another host on the Internet, it must first know its address, and the IP address in TCP/IP is composed of four paragraphs. Separate number composition (IPv4 address as an example, IPv6 address), remember, is not always as convenient as the name, so the domain name system is used to manage the corresponding relationship between name and IP.

Although all nodes on the Internet can be identified by and accessed through IP addresses, even a 32-bit binary IP address written as four ten digits of 0 to 255 is still too long and difficult to remember. Therefore, Domain names were invented to associate an IP address with a set of meaningful characters. When users visit a website, they can enter the website's IP address or domain name, which is equivalent to access.

Custom DNS

If you are on the same network, you may encounter that all other devices can access the Web page, but one computer or mobile phone can not. In this case, you can check whether the mobile phone or computer's DNS configuration is correct or manually add the DNS server address.

For example, we can use Google public DNS of 8.8.8.8 and 8.8.4.4 to avoid DNS resolving problems. Some websites or applications require specific DNS resolution. You can consult your ISP or mobile carrier for details.

We can either set custom DNS servers on the phones and computers or set custom DNS on the router. Then, we will use the DNS resolving services from the custom DNS server instead of the ISP or carrier's DNS service.

To custom the router's DNS settings, log into the router and follow the below steps:

1. Navigate to "Network > Interfaces > LAN: Edit"

2. Input the DNS on the field "Use custom DNS servers."

3. Click the "+" button to add more.

4. Click the "Save & Apply" button on the bottom right corner to take effect.

Add Custom DNS Servers On SIM Router's LAN Interface