In this post I would be showin you the steps needed to create a tunnel between Linux and Windows XP for safe data transmission with proper data encapsulation. We will be using Openswan on the Linux server and IPsec on the Windows XP to do so.
Linux side configuration
# yum -y install openswan
# vi /etc/ipsec.conf
version 2.0 # conforms to second version of ipsec.conf specification
# basic configuration
# Debug-logging controls: "none" for (almost) none, "all" for lots.
# plutodebug="control parsing"
# For Red Hat Enterprise Linux and Fedora, leave protostack=netkey
# Enable this if you see "failed to find any available worker"
Now you need to define the preshared key which will be used for authentication
: PSK "secretkey"
# service ipsec start
Windows XP side configuration
Now add "IP Security Policies on Local Computer"
Create a new IP security policy
Mention the preshared key as provided in ip.secrets on the linux server
Then you can click on Next and Finish the wizard.
Then you can finish the wizard and select this filter action for the IPsec policy.
Similarly create another IP Filter rule with the name "Linux to WinXP" and add the custom Filter action to this filter rule. The only thing you need to change is the filter properties.
Thats all, Now you can save and close the wizard. Right click the IP security rule you created and click on "Assign".
Now try to ping your server IP on the cmd prompt
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