Dynamic Public IPv4 vs CGNAT: How IP Addressing Affects Your nbn® Connection

An IPv4 address identifies your internet connection when it communicates with websites and online services.

A public IPv4 address is assigned directly to your internet service and can be reached across the public internet, subject to the firewall and security settings on your modem or router.

When the address is dynamic, it may change occasionally, for example, when your service reconnects or following a network event. While it is assigned to your service, however, it is not being shared with multiple unrelated customers through a provider-controlled CGNAT platform.

Your modem or router will still protect devices inside your home network using its firewall and local network address translation. The difference is that there is no additional CGNAT layer managed by the internet provider.

CGNAT stands for Carrier-Grade Network Address Translation. 

It allows an internet provider to share a limited number of public IPv4 addresses across multiple customers. Rather than receiving an individual public IPv4 address, each customer is assigned an address that operates inside the provider’s network. 

The provider then translates traffic from multiple customer connections through one or more shared public addresses. 

CGNAT helps providers manage the limited global supply of IPv4 addresses. It generally works well for standard internet activities, including: 

• Browsing websites 

• Streaming video 

• Using social media 

• Accessing cloud applications 

• Sending email 

Its limitations become more noticeable when a customer wants to accept an incoming connection from the internet. 

Better flexibility for online gaming 

Online games use a mixture of dedicated servers, peer-to-peer connections and player-hosted sessions. Consoles and gaming applications may also use automatic port mapping to support matchmaking, multiplayer sessions and voice communication.

CGNAT adds an additional translation layer that the customer cannot control. Depending on the game, platform and network design, this may contribute to:

• Strict or restricted NAT classifications

• Difficulty hosting multiplayer sessions

• Matchmaking problems

• Peer-to-peer connection issues

• Reliance on relay servers

A dynamic public IPv4 address does not automatically increase an nbn® plan’s speed or reduce latency. Those factors are affected by the access technology, plan speed, network conditions, Wi-Fi setup, game server location and other variables. Check our blog about nbn® speed tiers and nbn® access technology.

However, removing the provider-side CGNAT layer gives compatible games and consoles a better opportunity to establish direct connections. Check our blog about nbn® plans for gaming.

Greater control over port forwarding

Port forwarding allows selected incoming internet traffic to be directed to a particular device or application inside a home network.

It may be used for:

• Private game servers

• Home VPN connections

• Network-attached storage

• Personal servers

• Security camera systems

• Remote desktop applications

• Specialist smart-home systems

With a public IPv4 address, port-forwarding rules can generally be configured through a compatible modem or router.

Under CGNAT, changing the settings on the home router may not be enough. The incoming connection must also passes through the provider’s CGNAT platform, and residential customers do not normally control the port mappings on that platform.

A dynamic public IPv4 address gives customers more direct control over their own network configuration.

More practical remote access

Remote access can be useful for customers who want to connect to their home network while they are away.

Examples include accessing:

• A home VPN

• Stored files

• A media server

• Home automation equipment

• Security cameras

• Remote-working systems

Because a dynamic IP address may change, customers who need a consistent destination can use a dynamic DNS service. Dynamic DNS associates a hostname with the connection’s current public IP address and updates the record when the address changes.

With CGNAT, dynamic DNS by itself is generally not enough. The public IP address is shared, and the customer cannot independently direct incoming connections through the provider’s CGNAT system.

For many residential applications, a dynamic public IPv4 address combined with dynamic DNS can provide a practical alternative to a static IP address.

Reduced exposure to shared IP reputation problems

Online services may use public IP addresses as one of several signals when detecting spam, fraud, account abuse or excessive traffic.

Under CGNAT, many unrelated customers can appear to websites and online platforms as though they are connecting from the same public IPv4 address.

If another person using that shared address generates suspicious or abusive traffic, other customers may occasionally encounter:

• Additional CAPTCHA requests

• Temporary rate limits

• Login verification prompts

• Access restrictions

• Poor IP reputation warnings

These issues do not occur with every website or service, and any public IP address can potentially develop a poor reputation.

However, an individually assigned dynamic public IPv4 address reduces the risk of unrelated customers sharing the same public internet identity.

A simpler network configuration

Most home networks already use network address translation inside the modem or router.

CGNAT adds another translation layer inside the provider’s network. This can create a double-NAT environment in which part of the connection is managed outside the customer’s home network.

That additional layer may make advanced configuration and troubleshooting more complicated.

A dynamic public IPv4 address removes the provider-side CGNAT layer. Customers continue to manage their own modem, router, firewall and port-forwarding settings, but the path between the home service and the public internet is more direct. Read our guide on how to set up your nbn® modem.

A public IPv4 address does not mean that devices inside the home are automatically exposed to the internet. 

A properly configured modem or router will normally block unsolicited incoming traffic unless the customer deliberately enables port forwarding, remote administration or another inbound service. 

Customers should still follow standard security practices: 

• Keep modem, router and device firmware updated 

• Use strong, unique passwords 

• Enable multi-factor authentication where available 

• Disable remote administration unless it is required 

• Only open ports that are necessary 

• Remove port-forwarding rules that are no longer used 

• Use a properly configured VPN for sensitive remote access 

• Avoid exposing device administration pages directly to the internet 

CGNAT can act as an additional barrier to unsolicited incoming connections, but it should not be treated as a replacement for a firewall, software updates or secure account settings. 

A dynamic public IPv4 address is not the same as a static IP address. 

A dynamic public IPv4 address: 

• Is publicly routable 

• Is assigned to the customer’s service while in use 

• May change following a reconnection or network event 

• Can support many residential networking applications 

• Can be paired with dynamic DNS when a consistent hostname is required 

A static public IPv4 address: 

• Remains the same 

• Provides a permanently predictable endpoint 

• May be preferable for business systems, IP allowlists, specialist servers and site-to-site VPNs. Read our guide about business vs residential nbn® and Yomojo Business nbn® 

• Is usually offered as a separate paid feature where available 

Most residential customers do not require a static IP address. A dynamic public IPv4 address provides many of the practical benefits of public connectivity without requiring the address to remain permanently fixed. 

CGNAT is a legitimate way for providers to conserve scarce IPv4 addresses, and it may not affect customers who only use standard internet applications. 

However, it can limit activities that rely on inbound or peer-to-peer connectivity. 

Yomojo supplies residential nbn customers with a dynamic public IPv4 address rather than placing those services behind CGNAT. 

This provides greater flexibility for: 

• Online gaming 

• Port forwarding 

• Home VPNs 

• Remote access 

• Personal servers 

• Network storage 

• Security systems 

• Smart-home applications 

• Advanced network troubleshooting 

The IP address may change occasionally, but customers retain the ability to configure supported inbound connections through their own compatible networking equipment. 

Choose a Yomojo residential nbn® service and retain greater control over how your home connects to the internet.