Elastic network interfaces
An elastic network interface is a logical networking component in a VPC that represents a virtual network card. You can create and configure network interfaces and attach them to instances that you launch in the same Availability Zone. The attributes of a network interface follow it as it's attached or detached from an instance and reattached to another instance. When you move a network interface from one instance to another, network traffic is redirected from the original instance to the new instance.
Note that this AWS resource is referred to as a network interface in the AWS Management Console and the Amazon EC2 API. Therefore, we use "network interface" in this documentation instead of "elastic network interface". The term "network interface" in this documentation always means "elastic network interface".
Network interface attributes
A network interface can include the following attributes:
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A primary private IPv4 address from the IPv4 address range of your subnet
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A primary IPv6 address from the IPv6 address range of your subnet
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Secondary private IPv4 addresses from the IPv4 address range of your subnet
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One Elastic IP address (IPv4) for each private IPv4 address
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One public IPv4 address
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Secondary IPv6 addresses
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Security groups
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A MAC address
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A source/destination check flag
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A description
Monitoring traffic
You can enable a VPC flow log on your network interface to capture information about the traffic going to and from a network interface. After you've created a flow log, you can view and retrieve its data in Amazon CloudWatch Logs. For more information, see VPC Flow Logs in the Amazon VPC User Guide.
Contents
- Network interface concepts
- Network cards
- Maximum IP addresses per network interface
- Create a network interface for your Amazon EC2 instance
- Manage the IP addresses for your network interface
- Modify network interface attributes
- Multiple network interfaces for your Amazon EC2 instances
- Requester-managed network interfaces
- Prefix delegation for Amazon EC2 network interfaces
- Delete a network interface
Network interface concepts
The following are important concepts to understand as you get started using network interfaces.
- Primary network interface
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Each instance has a default network interface, called the primary network interface. You can't detach a primary network interface from an instance.
- Secondary network interfaces
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You can create and attach secondary network interfaces to your instance. The maximum number of network interfaces varies by instance type. For more information, see Maximum IP addresses per network interface.
- IPv4 addresses for network interfaces
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When you launch an EC2 instance into an IPv4-only or dual stack subnet, the instance receives a primary private IP address from the IPv4 address range of the subnet. You can also specify additional private IPv4 addresses, known as secondary private IPv4 addresses. Unlike primary private IP addresses, secondary private IP addresses can be reassigned from one instance to another.
- Public IPv4 addresses for network interfaces
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All subnets have a modifiable attribute that determines whether network interfaces created in that subnet (and therefore instances launched into that subnet) are assigned a public IPv4 address. For more information, see Subnet settings in the Amazon VPC User Guide. When you launch an instance, the IP address is assigned to the primary network interface. If you specify an existing network interface as the primary network interface when you launch an instance, the public IPv4 address is determined by this network interface.
When you create a network interface, it inherits the public IPv4 addressing attribute from the subnet. If you later modify the public IPv4 addressing attribute of the subnet, the network interface keeps the setting that was in effect when it was created.
- IPv6 addresses for network interfaces
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If you associate IPv6 CIDR blocks with your VPC and subnet, you can assign IPv6 addresses from the subnet range to a network interface. Each IPv6 address can be assigned to one network interface.
All subnets have a modifiable attribute that determines whether network interfaces created in that subnet (and therefore instances launched into that subnet) are automatically assigned an IPv6 address from the range of the subnet. When you launch an instance, the IPv6 address is assigned to the primary network interface.
- Elastic IP addresses for network interfaces
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You can associate an Elastic IP address with one of the private IPv4 addresses for the network interface. You can associate one Elastic IP address with each private IPv4 address. If you disassociate an Elastic IP address from a network interface, you can release it or associate it with a different instance.
- Termination behavior
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You can set the termination behavior for a network interface that's attached to an instance. You can specify whether the network interface should be automatically deleted when you terminate the instance to which it's attached.
- Source/destination checking
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You can enable or disable source/destination checks, which ensure that the instance is either the source or the destination of any traffic that it receives. Source/destination checks are enabled by default. You must disable source/destination checks if the instance runs services such as network address translation, routing, or firewalls.
- Requester-managed network interfaces
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These network interfaces are created and managed by AWS services to enable you to use some resources and services. You can't manage these network interfaces yourself. For more information, see Requester-managed network interfaces.
- Prefix delegation
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A prefix is a reserved private IPv4 or IPv6 CIDR range that you allocate for automatic or manual assignment to network interfaces that are associated with an instance. By using Delegated Prefixes, you can launch services faster by assigning a range of IP addresses as a single prefix.
Network cards
Most instance types support one network card. Instance types that support multiple network cards provide higher network performance, including bandwidth capabilities above 100 Gbps and improved packet rate performance. When you attach a network interface to an instance that supports multiple network cards, you can select the network card for the network interface. The primary network interface must be assigned to network card index 0.
If you enable Elastic Fabric Adapter (EFA) when you launch an instance that supports multiple network cards, all network cards are available. You can assign up to one EFA per network card. An EFA counts as a network interface.
The following instance types support multiple network cards.
| Instance type | Number of network cards |
|---|---|
c6in.32xlarge |
2 |
c6in.metal |
2 |
dl1.24xlarge |
4 |
g6e.24xlarge |
2 |
g6e.48xlarge |
4 |
hpc6id.32xlarge |
2 |
hpc7a.12xlarge |
2 |
hpc7a.24xlarge |
2 |
hpc7a.48xlarge |
2 |
hpc7a.96xlarge |
2 |
m6idn.32xlarge |
2 |
m6idn.metal |
2 |
m6in.32xlarge |
2 |
m6in.metal |
2 |
p4d.24xlarge |
4 |
p4de.24xlarge |
4 |
p5.48xlarge |
32 |
r6idn.32xlarge |
2 |
r6idn.metal |
2 |
r6in.32xlarge |
2 |
r6in.metal |
2 |
trn1.32xlarge |
8 |
trn1n.32xlarge |
16 |
u7in-16tb.224xlarge |
2 |
u7in-24tb.224xlarge |
2 |
u7in-32tb.224xlarge |
2 |
