Create Subnets for the SBC SWe

Overview

An SBC SWe deployment requires a VPC with sufficient IP space to support four or five IPv4 subnets:

• Management (MGT0)
• High Availability (HA0)
• Packet 0 (PKT0)
• Packet 1 (PKT1)
• High-Availability-forwarding Engine Public Subnet (HFE Public-facing), depending on the deployment type

Using HFE

If you choose HFE, the following applies:

• You must use a different private pkt0 subnet for each SBC HA pair. HA0, pkt1 and MGT0 subnets are sharable with other SBCs.
• HFE templates create private pkt0 subnets for each SBC HA pair (when using the AWS_HFE_HA_template_auto_subnet.json template). 
• You can create pkt0 private subnets before creating SBC and HFE. In this scenario, use HFE - AWS_HFE_HA_template.json to create an HFE HA pair with the subnets you provide.

If you choose to create private pkt0 subnets before creating SBC with HFE, consider the following:

• Private subnet – A subnet without any Internet GW attached to it, the routing table of the subnet can contain routing information only for VPC/subnets.

  • Example routing table for a private subnet:

    Destination	Target
    10.54.0.0/16	local

  • In the above example, no 0.0.0.0/0 rule is added to the routing table. Plus. there is no rule to send traffic to the Internet GW; only rule present here is "10.54.0.10/16 - local".
• The suggested CIDR is /26 /27 (Using /24 or larger CIDR will waste many IP addresses)
• Ribbon recommends using AWS_HFE_HA_template_auto_subnet.json to create the pkt0 private subnet while creating the SBC instance.  

Procedure

Create a subnet within an existing VPC, or allocate a new VPC. All four subnets must reside within the same region/VPC and availability zone.

To create a new subnet with CIDR x.x.x.x/20 within an existing VPC:

1. Navigate to the VPC Dashboard: https://console.aws.amazon.com/vpc/
   
   
   
2. Select Your VPCs on the left taskbar to see the list of VPCs available.
   
   
   
3. Select Subnets on the left taskbar.
4. Click Create subnet to create a subnet for MGT0 using a CIDR block. For example, x.x.0.0/20.
   
   
   
5. Click Create subnet to create a subnet for HA0 using an IPv4 CIDR block, for example, x.x.16.0/20.
6. Click Create subnet to create a subnet for PKT0 using an IPv4 CIDR block, for example, x.x.32.0/20.
7. Click Create subnet to create a subnet for PKT1 using an IPv4 CIDR block, for example,  x.x.48.0/20.
   
   
   
8. If deploying a High-Availability Forwarded Engine instance with the SBC, use a public-facing subnet. You can re-use an existing public-facing subnet. If not available, click Create subnet to create a subnet for HFE Public-facing using an IPv4 CIDR block, for example, x.x.64.0/20
   
   

For more information on creating subnets in AWS, refer to Creating a Subnet in Your VPC.