OpenSwan on AWS

A common use case for using a third party VPN solution such as OpenSwan is to connect two regions VPCs through the use of an IPSec VPN server.  

First, set up a VPC in both regions with, here is what I did:

Region 1 (US-West-2) - VPC 10.0.0.0/16 with private subnet 10.0.0.0/24

Region 2 (Australia)- VPC 172.0.0.0/16 with private subnet 172.0.0.0/24

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Configure the VPN server software for the EC2 instances - Region 1

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Step 1
------
sudo yum install openswan

Step 2
------
nano /etc/ipsec.conf

Step 3
------
sudo vi /etc/ipsec.d/vpc1-to-vpc2.conf

Step 4
------
conn vpc1-to-vpc2
 type=tunnel
 authby=secret
 left=%defaultroute
 leftid=<EIP1>
 leftnexthop=%defaultroute
 leftsubnet=<VPC1 CIDR>
 right=<EIP2>
 rightsubnet=<VPC2 CIDR>
 pfs=yes
 auto=start

Step 5
------
sudo vi /etc/ipsec.d/vpc1-to-vpc2.secrets

Step 6
------
<EIP1> <EIP2>: PSK "<TYPE A KEY HERE>"

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Configure the VPN server software for the EC2 instances - Region 2

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Step 7
------
sudo vi /etc/ipsec.d/vpc2-to-vpc1.conf

Step 8
------
conn vpc2-to-vpc1
 type=tunnel
 authby=secret
 left=%defaultroute
 leftid=<EIP2>
 leftnexthop=%defaultroute
 leftsubnet=<VPC2 CIDR>
 right=<EIP1>
 rightsubnet=<VPC1 CIDR>
 pfs=yes
 auto=start

Note the CIDR needs to include the block range. For example: 10.0.0.0/16

Step 9
------
sudo vi /etc/ipsec.d/vpc2-to-vpc1.secrets

Step 10
-------
<EIP2> <EIP1>: PSK "<TYPE THE SAME KEY FROM STEP 6 HERE>"

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Configuration in each region

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Step 11
-------
a-
sudo service ipsec start

b-
sudo chkconfig ipsec on

c-
sudo vi /etc/sysctl.conf

net.ipv4.ip_forward = 1

d-
sudo service network restart


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Test your connections

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Step 1 - Region 1
------
ping 172.0.0.50

Step 2 - Region 2

ping 10.0.0.50