Between two boxes manually

Suppose we have two boxes, A and B, and we want to establish IPsec between them.

Here's how:

1. On each box, create a script file (let's say its name is my_script) having the following content:

   #!/bin/ksh 
   # args: This script takes two arguments:
   #    - The first one is the IP address of the box that is to
   #      run it on.  
   #    - The second one is the IP address of the box that this
   #      box is to establish IPsec connection to.
   Myself=$1
   Remote=$2
   
   # The following two lines are to clean the database.
   # They're here simply to demonstrate the "hello world" level
   # connection.
   #  
   setkey -FP
   setkey -F
   
   # Use setkey to input all of the SA content.
   setkey -c << EOF
   
   spdadd $Myself $Remote any -P out ipsec esp/transport/$Myself-$Remote/require;
   spdadd $Remote $Myself any -P in ipsec esp/transport/$Remote-$Myself/require;
   
   add  $Myself $Remote esp 1234 -m any -E 3des-cbc "KeyIsTwentyFourBytesLong";
   add  $Remote $Myself esp 1234 -m any -E 3des-cbc "KeyIsTwentyFourBytesLong";
   EOF
     

2. On BoxA, run ./my_script BoxA BoxB, or give the IP address of each box if the name can't be resolved.
3. Similarly, on BoxB, run ./my_script BoxB BoxA.

Now you can check the connection by pinging each box from the other. You can get the IPsec status by using setkey -PD.