Podcast
Questions and Answers
What is ClassicLink?
What is ClassicLink?
What does ClassicLink cost?
What does ClassicLink cost?
No additional charge, but existing cross Availability Zone data transfer charges apply.
How do I use ClassicLink?
How do I use ClassicLink?
Enable at least one VPC for ClassicLink and associate a Security Group from that VPC with the EC2-Classic instance.
Does the EC2-Classic instance become a member of the VPC?
Does the EC2-Classic instance become a member of the VPC?
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Can I use EC2 public DNS hostnames from my EC2-Classic and EC2-VPC instances to address each other?
Can I use EC2 public DNS hostnames from my EC2-Classic and EC2-VPC instances to address each other?
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Are there any VPCs for which I cannot enable ClassicLink?
Are there any VPCs for which I cannot enable ClassicLink?
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Can traffic from an EC2-Classic instance travel through the Amazon VPC and use the Internet gateway?
Can traffic from an EC2-Classic instance travel through the Amazon VPC and use the Internet gateway?
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Does ClassicLink affect access control between EC2-Classic instances?
Does ClassicLink affect access control between EC2-Classic instances?
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Will ClassicLink settings on my EC2-Classic instance persist through stop/start cycles?
Will ClassicLink settings on my EC2-Classic instance persist through stop/start cycles?
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Will my EC2-Classic instance be assigned a new private IP address after enabling ClassicLink?
Will my EC2-Classic instance be assigned a new private IP address after enabling ClassicLink?
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Does ClassicLink allow EC2-Classic Security Group rules to reference VPC Security Groups?
Does ClassicLink allow EC2-Classic Security Group rules to reference VPC Security Groups?
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Study Notes
ClassicLink Overview
- ClassicLink connects EC2 instances on the EC2-Classic platform with instances in a VPC using private IP addresses.
- Requires enabling ClassicLink for a VPC and associating a Security Group from the VPC with an EC2-Classic instance.
Pricing Information
- No extra charge for ClassicLink use, but data transfer charges between Availability Zones apply.
Usage Steps
- Enable at least one VPC for ClassicLink in your account.
- Associate a Security Group from the VPC to the desired EC2-Classic instance.
- An EC2-Classic instance can only be linked to one VPC at a time.
Membership and Security Groups
- An EC2-Classic instance does not become a part of the VPC; it joins the VPC Security Group associated with it.
- All VPC Security Group rules govern communication with the EC2-Classic instance.
DNS and IP Communication
- EC2 public DNS hostnames do not resolve to private IP addresses across EC2-Classic and EC2-VPC instances.
VPC Eligibility
- ClassicLink cannot be enabled for VPCs with a CIDR in the 10.0.0.0/8 range, except for 10.0.0.0/16 and 10.1.0.0/16.
- VPCs with route table entries directing to the 10.0.0.0/8 CIDR to non-local targets cannot enable ClassicLink.
Traffic Routing
- Traffic from EC2-Classic instances can only route to private IPs within the VPC.
- Cannot route traffic to external destinations such as internet gateways or peered VPCs.
Access Control
- ClassicLink does not alter the existing Security Group access control for EC2-Classic instances.
Instance Cycles
- ClassicLink connections do not persist through stop/start cycles; they need to be re-established.
- Connection does persist through instance reboots.
IP Addressing
- Enabling ClassicLink does not assign a new private IP address; the existing private IP remains for communication with VPC resources.
Security Group References
- EC2-Classic Security Group rules cannot reference VPC Security Groups and vice versa.
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Description
This quiz covers the essential aspects of ClassicLink, including how it connects EC2 instances on the EC2-Classic platform with those in a VPC. Learn about pricing, usage steps, security group associations, and important DNS considerations. Perfect for understanding VPC connectivity and management.
