Virtual Network NAT is a fully managed and highly resilient Network Address Translation (NAT) service. VNet NAT simplifies outbound Internet connectivity for virtual networks. When configured on a subnet, all outbound connectivity uses the VNet NAT's static public IP addresses.
NAT gateway provides outbound internet connectivity for one or more subnets of a virtual network. Once the NAT gateway is associated with a subnet, NAT provides source network address translation (SNAT) for that subnet. NAT gateway specifies which static IP addresses virtual machines use when creating outbound flows. Static IP addresses come from public IP addresses, public IP prefixes, or both. If a public IP prefix is used, all IP addresses of the entire public IP prefix are consumed by a NAT gateway. A NAT gateway can use a total of up to 16 static IP addresses from either.
How does virtual networking work?
Virtual networking is a technology that allows multiple devices to communicate with each other on a shared network infrastructure. It creates a virtual network environment on top of a physical network, enabling organizations to isolate and manage different network segments.
The process of virtual networking involves:
Physical Network Infrastructure
This consists of physical hardware components like routers, switches, and servers that form the backbone of the network. These devices are interconnected using cables or optical fibres, creating a physical network topology.
Virtualization Layer
A virtualization software layer is installed on the physical network to create virtual network segments or virtual machines. This layer acts as a bridge between the physical and virtual worlds, translating physical network resources into virtual network resources.
Virtual Network Creation
The virtualization software divides the physical network resources into multiple virtual networks, each with its own isolated configuration, security settings, and routing protocols. This process is known as network segmentation or network virtualization. Each virtual network is treated as a separate logical network, isolated from other virtual networks and the underlying physical network.
Device Connection
Virtual machines or other devices are connected to the virtual networks. They communicate with each other within the virtual environment, unaware of the underlying physical network. This allows for efficient and secure communication between devices without the need for complex physical network configurations.
Types of virtual networks
A network's hardware devices usually define the three common types of virtual networks.
Virtual private network (VPN)
A VPN utilizes the internet to connect two networks or to connect remote clients to central networks. VPNs establish a secure and encrypted connection between two endpoints, ensuring privacy by concealing traffic. When using a VPN, all network services on each end of the connection appear as local services, but they are hidden in between. A VPN forms an encrypted tunnel between two endpoints.
Virtual LAN (VLAN)
Separating devices or endpoints within a network for improved security and management is made possible by a virtual local area network (VLAN). Network traffic is marked at Layer 2 by VLANs, enclosing the packets so that the traffic is only exchanged between the VLAN-tagged ports and devices. A network can support up to 4,000 VLAN segments. A VLAN facilitates the segmentation of endpoints and traffic within a network.
Virtual Extensible LAN
A VXLAN can establish a virtual network similar to a VLAN but goes further by encapsulating the media access control address in User Datagram Protocol.
While a VLAN is established over switch ports, a VXLAN generates virtual endpoints within switches or other Layer 3 devices. This allows a VXLAN to offer Layer 2 functionality at Layer 3, the Internet Protocol (IP) address layer. VXLANs offer more flexibility than VLANs and can expand to accommodate up to 16 million VXLAN segments per network.
Within switches, a VXLAN generates virtual endpoints.
These examples of standardized network virtualization all operate on top of network infrastructure, including routers, switches, and cabling.
However, another form of network virtualization is more proprietary and occurs within a hypervisor running virtual machines (VMs). The hypervisor is capable of creating its own virtual network, either an internal virtual network for communication exclusive to the local VMs or an external virtual network for communication beyond the hypervisor to the larger network.
A hypervisor is able to create its virtual network, which can be either internal or external.
Benefits of Virtual Networks
Virtual networks offer numerous benefits to organizations, including:
Flexibility
Virtual networks provide unparalleled flexibility, allowing organizations to easily create, modify, and scale their network infrastructure to meet evolving business needs. This agility enables businesses to rapidly adapt to market changes, introduce new products or services, and respond to unforeseen challenges.
Isolation
Virtual networks offer a high degree of isolation, ensuring that different network segments are securely separated from each other. This prevents unauthorized access, minimizes the impact of security breaches, and protects sensitive data.
Cost-Efficiency
Virtual networks can significantly reduce hardware costs by consolidating multiple network functions onto a single physical infrastructure. This eliminates the need for redundant equipment and reduces ongoing maintenance expenses.
Scalability
Virtual networks are highly scalable, allowing organizations to easily adjust their network capacity to accommodate increasing or decreasing workloads. This ensures optimal performance and resource utilization while avoiding the costs and complexities of overprovisioning.
Improved Management
Virtual networks streamline network management by providing centralized control and automation. This reduces the administrative burden on IT teams, improves operational efficiency, and enables faster troubleshooting and problem resolution.
Enhanced Security
Virtual networks can implement robust security measures to protect sensitive data and prevent unauthorized access. Features such as firewalls, intrusion detection systems, and encryption can be easily deployed and managed within the virtual environment, providing a comprehensive security framework.
what is Network Address Translation (NAT)
Network Address Translation (NAT) is a fundamental networking technology that enables private IP networks to connect to the public internet while conserving the limited pool of available public IP addresses. NAT acts as a translator, mapping private IP addresses within a local network to a single or multiple public IP addresses before packets are sent to the external network. This translation process allows multiple devices on a private network to share a single public IP address, effectively hiding the internal network from the outside world.
What are Private IP Addresses?
As the Internet gained popularity in previous years, the group responsible for managing IP addresses, known as the Internet Assigned Numbers Authority (IANA), realized the need for action. Consequently, they devised a network address translation scheme, detailed in a document called Request for Comments (RFC) 1918. This document is one of many that outlines the functioning of the Internet. RFC 1918 is the required document for all router manufacturers to implement if they want to understand NAT. Regardless of the type of NAT used, private IP addresses are utilized.
Sending a private IP address onto the internet is akin to sending physical mail with an "anonymous" return address and requesting a return service notification. In a scenario with traditional mail service, you wouldn't receive the return service notification because the service wouldn't know where "anonymous" is located.
How Does NAT Work?
The laptop is connected to a home network using Network Address Translation (NAT). Connected to a router that addresses the internet. When someone uses the laptop to search for directions to their favourite restaurant, the laptop, using NAT, sends this request in an IP packet to the router. The router then passes that request along to the internet and the search service. Before the request leaves the home network, the router changes the internal IP address from a private local IP address to a public IP address. The router effectively translates the private address to one that can be used on the internet, and vice versa.
1Inside your modest cable modem or DSL router, there is an automated translator in operation. If the packet retains a private address, the receiving server will not have the information necessary to send the data back.
This is due to the fact that a private IP address is unable to be directed onto the internet. If your router attempted to do so, all internet routers are designed to automatically reject private IP addresses. The good news is that modern routers designed for home offices and small offices can easily convert between private IP addresses and publicly-routed IP addresses.
Network Address Translation Types
Static NAT
One-to-one mapping
Static NAT establishes a permanent association between a specific private IP address and a dedicated public IP address. This allows devices on the private network to have their own unique public IP addresses, enabling direct communication with external systems.
Dedicated public IP
Each device on the private network is assigned a unique public IP address, providing a consistent and predictable identity for external connections. This is particularly useful for hosting public-facing services, such as web servers, email servers, or remote access services.
Dynamic NAT
Pool of public IP addresses
Dynamic NAT utilizes a pool of public IP addresses to translate private IP addresses. This allows multiple devices on the private network to share a limited number of public IP addresses, conserving the available address space.
Dynamic Assignment
Public IP addresses are dynamically assigned to private IP addresses on an as-needed basis. When a device on the private network initiates a connection to the internet, a public IP address from the pool is allocated to it. This ensures that only devices that require internet access are assigned public IP addresses, optimizing resource utilization.
Port Address Translation (PAT)
Many-to-one mapping
PAT allows multiple private IP addresses to share a single public IP address by using different port numbers. This enables a large number of devices on the private network to connect to the internet using a limited number of public IP addresses, maximizing the efficiency of address utilization.
Efficient use of public IP addresses
PAT significantly reduces the number of public IP addresses required for a private network, making it an economical solution for organizations with limited address space. By sharing a single public IP address among multiple devices, PAT minimizes the costs associated with acquiring and managing public IP addresses.
Why Use NAT?
NAT, or Network Address Translation, is a fundamental process used in networking to allow multiple private devices to share a single public IP address. This is commonly implemented by consumer routers and networking equipment, enabling multiple devices in a home or office to access the Internet using a single public IP address.
When you purchase routing equipment from a store, the NAT functionality is often built into the device. It can be enabled automatically or with a simple configuration through the device's software interface.
To further explore NAT's role, it's important to understand its contribution to conserving IPv4 addresses. With the increasing scarcity of available IPv4 addresses due to the proliferation of internet-connected devices, NAT allows multiple devices within a private network to share a single public IP address, thus conserving this limited resource.
Additionally, while NAT does provide a level of security by concealing the internal IP addresses of devices from external networks, it has a limited role in providing comprehensive security services. NAT primarily serves as a first line of defense by obscuring internal network details, but it's not a comprehensive security solution on its own.
NAT Gateway benefits
Security
With NAT, individual VMs (or other compute resources) do not need public IP addresses and can remain fully private. Such resources without a public IP address can still reach external sources outside the VNet. You can also associate a Public IP Prefix to ensure that a contiguous set of IPs will be used for outbound. Destination firewall rules can then be configured based on this predictable IP list.
Resiliency
NAT is a fully managed and distributed service. It doesn't depend on any individual compute instances, such as VMs or a single physical gateway device. It leverages software-defined networking, making it highly resilient.
Scalability
NAT can be associated with a subnet and can be used by all compute resources in that subnet. Further, all subnets in a VNet can leverage the same resource. When associated with a Public IP Prefix, it will automatically scale to the number of IP addresses needed for outbound.
Performance
NAT will not impact the network bandwidth of your computing resources since it is a software-defined networking service.
Connecting with Azure services
When connecting to Azure services from your private network, the recommended approach is to use Private Link. Private Link lets you access services in Azure from your private network without the use of a public IP address.
Connecting to the internet
NAT is recommended for outbound scenarios and all production workloads where you need to connect to a public endpoint. The following scenarios are examples of how to ensure the coexistence of inbound with NAT gateway for outbound.
IP Conservation
IP addresses are used to identify each device that is connected to the internet. The current version of IP, IPv4, utilizes 32-bit numbered IP addresses, which provides for 4 billion potential IP addresses. This quantity appeared to be more than sufficient when it was introduced in the 1970s.
Nevertheless, with the expansion of the internet, the number of devices accessing it has increased significantly. While not all 7 billion people on the planet regularly use the internet, those who do often have multiple connected devices, such as phones, personal desktops, work laptops, tablets, TVs, and even refrigerators.
As a result, the number of devices accessing the internet far exceeds the number of available IP addresses. To address this, routing all of these devices via one connection using Network Address Translation (NAT) helps to merge multiple private IP addresses into one public IP address. This process aids in maintaining a higher availability of public IP addresses, even as private IP addresses continue to increase in number.
IPv6: More Addresses and Routing Efficiency
June 6, 2012, saw the official launch of IP version 6 (IPv6) after years of development. IPv6 was developed for several reasons, one was to address the need for more IP addresses, as traditional NAT could not keep up with demand. IPv6 uses 128-bit numbered IP addresses, allowing for a significantly larger number of potential IP addresses compared to IPv4. This process will take many years to complete, so using NAT for IPv4 addresses will continue to be common practice until then. Furthermore, IPv6 not only provides a much larger IP address space but also enhances routing efficiency. For instance, IPv6 reduces the burden on routers to process traffic compared to IPv4.
NAT and Security
NAT and private IP addresses are not themselves security measures. However, using NAT and private IP addresses is often seen as an initial step toward security. NAT transfers data packets from public to private addresses, which helps prevent external computers from directly accessing your personal device. For instance, someone on the internet cannot use ping or a web browser to connect to your home computer unless you set up a very specific mapping.
It's essential to recognize that NAT alone does not offer security measures such as firewalling, monitoring, antivirus protection, intrusion detection, application security, or zero trust services. It's best to think of NAT as a service that manages and conserves IP addresses rather than securing information or privacy. The confusion regarding whether NAT provides security measures stems from its implementation of private IP addresses. While "private" might suggest security and privacy, in practical terms, NAT does not provide security measures. Instead, it enables you to use private addresses.
NAT Gateway Use Case
NAT and VM with instance-level Public IP – In this scenario, VM will use NAT gateway for outbound. Inbound originated isn't affected.
NAT and VM with Standard Public Load Balancer – in this scenario, Any outbound configuration from a load-balancing rule or outbound rules is superseded by NAT gateway. Inbound originated isn't affected.
NAT and VM with instance-level Public IP and Standard Public Load Balancer – in this scenario, Any outbound configuration from a load-balancing rule or outbound rules is superseded by NAT gateway. The VM will also use NAT gateway for outbound. Inbound originated isn't affected.
NAT Gateway Monitoring - A network security group allows you to filter inbound and outbound traffic to and from a virtual machine. To monitor outbound traffic flowing from NAT, you can enable NSG flow logs.
NAT Gateway Performance - Each NAT gateway can provide up to 50 Gbps of throughput. You can split your deployments into multiple subnets and assign each subnet or group of subnets a NAT gateway to scale out.Each NAT gateway can support 64,000 flows each for TCP and UDP per assigned outbound IP address.
NAT Gateway Limitations
Basic load balancers and basic Public IP addresses are not compatible with NAT. Use standard SKU load balancers and Public IPs instead.
IP fragmentation isn't available for the NAT gateway.
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