Linux (CentOS Openswan) Example Using IKE2 and Preshared keys

yum install openswan

(strongswan is much nicer, but not in yum on centos5. On centos6, use strongswan)

In /etc/ipsec.conf uncomment

include /etc/ipsec.d/*.conf

Put following two files in /etc/ipsec.d/:

file: myFireBrick.conf:

 conn myFireBrick
        authby=secret
        auto=start
        ikev2=insist
        left=CentOS.IP.Address
        leftid=CentOS.IP.Address
        leftsubnet=CentOS.IP.Address/32
        right=FireBrick.IP.Address
        rightid=FireBrick.IP.Address
        rightsubnet=FireBrick.LAN.SUBNET/24

file: myFireBrick.secrets:

CentOS.IP.Address FireBrick.IP.Address : PSK "YourSecretHere"

chkconfig ipsec on
service ipsec start

Put the following in the FB at the other end:

 <connection name="IPSec" peer-ips="CentOS.IP.Address" auth-method="Secret" secret="YourSecretHere" local-ip="FireBrick.LAN.IP.Address" routes="CentOS.IP.Address" log="default"/>

strongSwan

file: /etc/ipsec.conf

conn myFireBrick
       authby=secret
       auto=start
       left=strongSwan.IP
       leftid=strongSwan.IP
       leftsubnet=strongSwan.IP
       right=FireBrick.IP
       rightid=FireBrick.IP
       rightsubnet=FireBrick.LAN.IP.Address/24
       lifetime=2m

file: /etc/ipsec.secrets

 strongSwan.IP FireBrick.IP : PSK "YourSecretHere"

Put the following in the FB at the other end:

 <connection name="IPSecTostrongSwan" peer-ips="strongSwan.IP" auth-method="Secret" secret="YourSecretHere" local-ip="FireBrick.LAN.IP.Address" routes="strongSwan.IP" log="default"/>