Site To Site VPN (AWS managed VPN)

AWS Details: https://docs.aws.amazon.com/vpn/latest/s2svpn/VPNTunnels.html

• Install Openswan (details: https://www.openswan.org/)

$ sudo su
$ yum install openswan

• Update /etc/sysctl.conf:

net.ipv4.ip_forward=1net.ipv4.conf.all.accept_redirects=0net.ipv4.conf.all.send_redirects=0

• Restart network service

$ service network restart

• VPC A: Create VGW, Customer Gateway and a VPN Connection. Download `generic` configuration  

• Configure Openswan ( IPSec tunnels ) based on the information provided in the downloaded configuration:

• $ vi /etc/ipsec.d/aws-vpn.conf:

 conn Tunnel1

authby=secret auto=start left=%defaultroute leftid=<Customer Gateway IP> right=<AWS Virtual Private gateway IP> type=tunnel ikelifetime=8h keylife=1h phase2alg=aes128-sha1;modp1024 ike=aes128-sha1;modp1024 keyingtries=%forever keyexchange=ike leftsubnet=<Customer CIDR> rightsubnet=<AWS VPC CIDR> dpddelay=10 dpdtimeout=30 dpdaction=restart_by_peer

• $ vi /etc/ipsec.d/aws-vpn.secrets

 <Customer gateway IP> <AWS VGW IP>: PSK "<Pre-Shared Key>"

• $ chkconfig ipsec on
• $ service ipsec start 
• $ service ipsec status