The set Entry

The set entry allows you to associate a string with a variable; the string will replace references to the variable later in the text. For example,

    set ip = ip, ip vnet, vnet eth arp, arp eth, eth ethd, ethd sim;

    ...

    host h1n1;
      protocols = megtest vtcp, vtcp $ip;

means that the reference to $ip is replaced by the protocol stack on the right side of the set command, which is equivalent to the following

host h1n1;
      protocols = megtest vtcp, vtcp ip, ip vnet, vnet eth arp, arp eth, 
                  eth ethd, ethd sim;