OpenSwan Install and Configuration on Ubuntu between AWS VPC's

OpenSwan-guide

Required:
  An instance accessible with an EIP from each VPC network
  Unique and non-overlapping CIDR ranges
  Security Group allowing each others EIP (udp: 500,4500  and icmp: echo reply)
  Disable Source/Dest Check on each Openswan AWS instance
  Configure Routing Tables on each VPC  (add tables with associated subnets)

Remote Network A:  10.11.0.0/16   -> openswan instance id
Remote Network B:  10.10.0.0/16   -> openswan instance id

On Each Server:
Install Openswan
% sudo apt-get install openswan

update /etc/sysctl.conf
--------------------------
net.ipv4.ip_forward=1
net.ipv4.conf.all.accept_redirects = 0
net.ipv4.conf.all.send_redirects = 0
net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.eth0.send_redirects = 0
net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.eth0.accept_redirects = 0 
--------------------------
% sudo sysctl -p

edit /etc/ipsec.conf
Add line:   include /etc/ipsec.d/*.conf   (do not indent)


On Network A openswan side, create /etc/ipsec.d/to-networkB.conf:
conn to-networkB
         type=tunnel
         authby=secret
         left=10.10.0.21     ## <- the private IP of your openswan server Network A
         leftid=1.2.3.4      ## <- external IP of Network A
         leftsubnet=10.10.0.0/16
         right=5.6.7.8       ## <- the external IP of Network B
         rightsubnet=10.11.0.0/16
         pfs=yes
         auto=start
         
Add to /etc/ipsec.secrets file:
1.2.3.4 5.6.7.8: PSK "create_your_super_secret_phrase_here"


On Network B openswan side, create /etc/ipsec.d/to-networkA.conf:
conn to-networkA
         type=tunnel
         authby=secret
         left=10.11.0.25   ## <- the private IP of your openswan server Network B
         leftid=5.6.7.8    ## <- the external IP of Network B
         leftsubnet=10.11.0.0/16
         right=1.2.3.4     ## <- external IP of Network A
         rightsubnet=10.10.0.0/16
         pfs=yes
         auto=start
         
Add to /etc/ipsec.secrets file:
5.6.7.8 1.2.3.4: PSK "create_your_super_secret_phrase_here"

---------
On Both Servers

% service ipsec restart
Look at /var/log/syslog and auth.log  for connectivity errors and status

% ipsec auto --status
Test by pinging a host on the other side

Success!

Which ubuntu version have you tried this? I cant make ping to work from VPC 1 to 2 or vice versa with ubuntu 14.04
It just stays at "ipsec__plutorun: 104 "to-nv" #1: STATE_MAIN_I1: initiate"
Nov 21 17:25:32 ip-172-16-239-10 ipsec_setup: NETKEY support found. Use protostack=netkey in /etc/ipsec.conf to avoid attempts to use KLIPS. Attempting to continue with NETKEY
Nov 21 17:25:32 ip-172-16-239-10 ipsec_setup: Using NETKEY(XFRM) stack
Nov 21 17:25:32 ip-172-16-239-10 kernel: [284815.609461] Initializing XFRM netlink socket
Nov 21 17:25:32 ip-172-16-239-10 ipsec_setup: ...Openswan IPsec started
Nov 21 17:25:32 ip-172-16-239-10 ipsec__plutorun: adjusting ipsec.d to /etc/ipsec.d
Nov 21 17:25:32 ip-172-16-239-10 pluto: adjusting ipsec.d to /etc/ipsec.d
Nov 21 17:25:32 ip-172-16-239-10 ipsec__plutorun: 002 added connection description "o2nv"
Nov 21 17:25:32 ip-172-16-239-10 ipsec__plutorun: 104 "o2nv" #1: STATE_MAIN_I1: initiate