What is the difference between public and private IP addresses?

Public IP addresses are internet-routable and can be accessed directly from the internet, making devices globally accessible but vulnerable to cyber attacks. Private IP addresses are NOT internet-routable and exist within specific ranges (10.x.x.x, 172.16-31.x.x, 192.168.x.x), providing inherent security by preventing direct internet access.

What is a fixed IP address for IoT SIM cards?

A fixed (or static) IP address remains constant and doesn't change over time, unlike dynamic IP addresses. For IoT applications requiring remote access (like CCTV systems or alarm monitoring), a fixed IP address is essential because it provides a consistent address for inbound connections to the device.

Why are public fixed IP addresses risky?

Public fixed IP addresses leave devices openly connectable from the internet, making them vulnerable to cyber attacks. Even with firewall protection, connection attempts consume data before being rejected, leading to excessive data fees. Additionally, IPv4 addresses are scarce and expensive due to the exhaustion of available address blocks.

How does Private Fixed IP with KeySecure provide secure remote access?

KeySecure provides secure VPN-based remote access to Private Fixed IP addresses without exposing devices to the public internet. Only authorized users you grant access can connect to your IoT devices, eliminating cyber attack risks and data consumption from unauthorized connection attempts while maintaining full remote management capabilities.

What happened to IPv4 address availability?

On November 25, 2019, RIPE NCC (the Regional Internet Registry for Europe, Middle East, and Central Asia) exhausted their last available IPv4 address blocks. All other regional registries had already exhausted their supplies in previous years. This makes IPv4 addresses increasingly scarce and expensive, trading at premium prices.

Public vs Private Fixed IP Addresses for IoT SIMs

Why IP Address Type Matters for IoT Security

Public Fixed IP SIM cards carry significant security risks that can be completely negated with a Private Fixed IP SIM. Understanding the fundamental differences between these two approaches is critical for protecting your IoT estate from cyber attacks while maintaining remote access capabilities.

Security First

Remote access to IoT devices is essential for management and monitoring, but implementing it securely requires understanding IP address fundamentals and the vulnerabilities associated with public internet exposure.

Understanding IP Addresses: The Foundation

An IP (Internet Protocol) address is a sequence of numbers similar to 192.168.0.1 allocated to a network device that uses a network or the internet for communication. The IP address assigned to a network device MUST be unique on the network it is connected to.

IPv4 Address Space Limitations

There are only approximately 4.3 billion possible unique IPv4 IP addresses in existence for use across the entire globe. These addresses are shared among internet-connected organizations worldwide and can only be allocated by organizations responsible for managing them.

Our partner ISP Faelix is one of these organizations authorized to allocate IP addresses from their assigned pool, enabling KeySIM to provide both public and private IP addressing solutions.

Public vs Private IP Addresses: Key Differences

Public IP Addresses

Internet-Routable Addresses

Can be described as "internet routable"
Directly connected to the public internet
Accessible from anywhere in the world
Visible and reachable globally
Subject to cyber attack attempts

Private IP Addresses

NOT Internet-Routable

Cannot be reached directly from the internet
Used within internal networks
Inherently protected from external attacks
Require VPN for remote access
Standard for home and business networks

Private IP Address Ranges

Three specific IP address ranges out of the approximately 4.3 billion possible addresses have been reserved for private use. These ranges are standardized globally and can be used by any organization internally:

10.0.0.0
to
10.255.255.255

Class A Private Range

172.16.0.0
to
172.31.255.255

Class B Private Range

192.168.0.0
to
192.168.255.255

Class C Private Range

Important: Private IP addresses look identical to public IP addresses in format—they're distinguished by falling within these reserved ranges. Your home network uses private IPs for all devices behind your router.

Dynamic vs Fixed (Static) IP Addresses

Both public and private IP addresses can be allocated in either dynamic or fixed (static) modes:

Dynamic IP Addresses

Change each time device connects
May change periodically during connection
Often shared across multiple devices
Standard for home broadband
Suitable for outbound-only connections

Fixed (Static) IP Addresses

Remain constant and never change
Dedicated to a single device/SIM
Enable reliable remote connections
Essential for inbound access
Required for IoT remote management

When Do You Need a Fixed IP?

Dynamic IP addresses work perfectly for browsing the internet because devices only make outbound connections. However, IoT applications often require inbound connections from the internet to the SIM.

Example: A CCTV recorder connected to a 4G router needs remote access from end users or an Alarm Receiving Centre. This requires a fixed (static) IP address to provide a consistent connection point.

Fixed IP Options for IoT SIM Cards

When allocating a fixed IP address to a SIM card, you have two primary options. Each has distinct advantages and significant disadvantages:

Option 1: Public Fixed IP Address

High Risk

Advantages

Maximum Flexibility: Accessible from any internet-connected device worldwide
Simple Sharing: Share IP address with third parties for immediate access
No VPN Required: Direct connection without additional software

Critical Disadvantages

Cyber Attack Vulnerability: Device openly connectable from entire internet
Excessive Data Fees: Data consumed even when firewall rejects attacks
IPv4 Scarcity: Addresses trade at premium prices and availability declining
Management Overhead: Requires constant firewall maintenance and monitoring

The Data Consumption Problem

Even with firewall protection configured to reject unauthorized connections, the damage is already done. Here's why:

Attacker sends connection request to your public IP address
Data packets travel across the internet to your 4G router
Mobile data is consumed transmitting these packets to your SIM
Router firewall finally rejects the connection
Result: You pay for data consumed by attack attempts, even though they were blocked

The IPv4 Exhaustion Crisis

With only 4.3 billion possible IPv4 addresses and billions of internet-connected devices, the address space is critically depleted:

November 25, 2019: RIPE NCC (Regional Internet Registry for Europe, Middle East, and Central Asia) exhausted their last available IPv4 address blocks.

Previous Years: All other Regional Internet Registries (RIRs) globally had already exhausted their supplies.

Impact: When ISPs run out of available IPv4 addresses in their allocations, there are no more to distribute. Existing addresses now trade at premium prices, and costs will only increase as scarcity worsens.

When Public Fixed IP Makes Sense

There are legitimate use cases for public fixed IP addresses, and KeySIM does offer them. However, we strongly encourage considering our secure alternatives that provide remote access without leaving devices vulnerable to cyber attacks or generating data fees from malicious traffic.

Option 2: Private Fixed IP Address with KeySecure

Recommended

KeySIM can assign Private Fixed IP addresses to your SIM cards, then provide secure remote access to those fixed IPs by utilizing our KeySecure functionality. This approach eliminates the vulnerabilities of public IP exposure while maintaining full remote management capabilities.

Key Advantages of Private Fixed IP

Enhanced Security

SIMs cannot be hit directly from public internet—only authorized KeySecure users can access your devices

Zero Attack Data Fees

No data consumption from unauthorized connection attempts or cyber attacks

Safe Router Configuration

Enable remote router management safely—only authorized users can access configuration interfaces

Cost Effective

More affordable than scarce IPv4 public addresses, with no premium pricing

No Additional Programming

Avoid complex firewall rules and port forwarding configurations

Granular Access Control

Grant and revoke access to specific users as needed through KeySecure portal

How KeySecure Private Fixed IP Works

Each IoT SIM is assigned a unique Private Fixed IP address from reserved ranges
Private IPs are NOT accessible from the public internet—protected by default
You grant access to specific users through the KeySecure portal
Authorized users connect via secure VPN tunnel to access your devices
All remote management happens over encrypted, authenticated connections

Our Team's Recommendation

Private Fixed IP addresses are considerably more secure than public IPs, avoid additional software complexity or programming overhead, and are significantly more cost-effective in both acquisition and ongoing data costs.

On this basis, our team believes you should use Private Fixed IPs wherever possible. For comprehensive information on private IP networking options, visit our KeySecure article.

Public vs Private Fixed IP: Side-by-Side Comparison

Feature	Public Fixed IP	Private Fixed IP + KeySecure
Internet Accessible	Yes - From Anywhere	Only via VPN
Cyber Attack Risk	High - Open to Internet	Minimal - Protected
Data Fees from Attacks	Yes - Costly	No
Setup Complexity	High - Firewall Rules	Simple - Grant Access
Cost	Premium - IPv4 Scarcity	Cost Effective
Access Control	Manual Firewall Config	Portal-Based
Remote Router Config	Risky - Avoid	Safe - Authorized Only
Ongoing Maintenance	High	Low

Common IoT Applications Requiring Fixed IP

CCTV & Surveillance

Remote access to security cameras and NVR systems requires fixed IP. Private Fixed IP with KeySecure protects systems from unauthorized access attempts.

Alarm Monitoring

Alarm Receiving Centres need reliable connections to monitored systems. Fixed IP ensures consistent connectivity without exposure to internet threats.

Industrial IoT

Remote monitoring and control of industrial equipment, sensors, and SCADA systems requires secure, reliable fixed IP addressing.

Making the Right Choice for Your IoT Deployment

Consider Public Fixed IP Only If:

You need universal access without VPN software
Third parties require direct IP access
You have robust firewall expertise and monitoring
You can afford premium IPv4 pricing
You accept elevated cyber attack risk

Choose Private Fixed IP If:

Security is a priority (it should be)
You want to control who accesses devices
Cost-effectiveness matters
You want to avoid data fees from attacks
You prefer simple, portal-based management

Public Fixed IP vs Private Fixed IP SIM Cards