To create a VPC peering connection with another VPC, you need to be aware of the following limitations and rules:
- You cannot create a VPC peering connection between VPCs that have matching or overlapping CIDR blocks.
- You cannot create a VPC peering connection between VPCs in different regions.
- You have a limit on the number active and pending VPC peering connections that you can have per VPC. For more information, see Amazon VPC Limits in the Amazon VPC User Guide.
- VPC peering does not support transitive peering relationships; in a VPC peering connection, your VPC does not have access to any other VPCs that the peer VPC may be peered with. This includes VPC peering connections that are established entirely within your own AWS account. For more information about unsupported peering relationships, see Invalid VPC Peering Connection Configurations. For examples of supported peering relationships, see VPC Peering Scenarios.
- You cannot have more than one VPC peering connection between the same two VPCs at the same time.
- The Maximum Transmission Unit (MTU) across a VPC peering connection is 1500 bytes.
- A placement group can span peered VPCs; however, you do not get full-bisection bandwidth between instances in peered VPCs. For more information about placement groups, see Placement Groups in the Amazon EC2 User Guide for Linux Instances.
- Unicast reverse path forwarding in VPC peering connections is not supported. For more information, see Routing for Response Traffic.
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