Virtual IP Address Reference
PureLoad 5.2 January 2015	http://www.pureload.com support@pureload.com

• Introduction
• Configuring IP addresses
  • Configuring Virtual IP Address in Windows XP/2000
  • Configuring Virtual IP Address in Linux
  • Configuring Virtual IP Address in Solaris
• Using IP Pool Tasks
  • IPPoolInitTask
  • PoolGetTask
  • PoolReturnTask

Introduction

If you test a server application that makes use of the client's IP addresses you need to configure your hosts to use virtual IP addresses.
A virtual IP address is an IP address that is not connected to a specific computer or network interface card (NIC) on a computer. Data packets are sent/received form/to the virtual IP address, but all packets travel through real network interfaces.

To be able to use virtual IP addresses mosts network tasks (including the HTTP tasks) allows setting the local IP address. There is also a set of tasks, the IP Pool tasks, to manage a pool of IP-addresses per PureLoad worker to make sure that parallels threads doesn't use the same IP address at the same time.

This document gives an introduction on how to set up virtual IP addresses and describes the IP Pool tasks.

Configuring IP addresses

How to configure virtual addresses is platform dependent and requires general knowledge on how your network is configured. If you want to create many virtual addresses in bulk and to keep the addresses permanently, you need to consult your OS documentation.

Still, this section gives you an overview on how this is done for a few different Operation Systems.

Configuring Virtual IP Address in Windows XP/2000

The procedure to configure virtual IP addresses under Windows XP/2000is as follows. This can be performed only by an user with admin privilege.  

1. Click on the Start Menu and choose Settings.
2. Among the listed items select Network and Dial-up connections.
3. Select Local area connection from the items under Network and Dial-up connections ; this opens with the general information on Local area connection status.
4. Click on the Properties button. The Local area connection properties dialog opens listing all the protocols.
5. Choose Internet Protocol ( TCP / IP ) and click on the Properties button.
6. The Internet Protocol TCP / IP Properties dialog is invoked. Click on the Advanced button at the bottom of the dialog.  The Advanced TCP / IP settings dialog displays all the configured IP addresses in your system.
7. Click Add button next to the displayed IP addresses to add an IP address with a corresponding sub-net mask.
   

You will have to re-start the system for the changes to take effect.

Configuring Virtual IP Address in Linux

To configure virtual IP addresses in Linux, you use the configured command with super user privilege.

For example if you network interface is eth0 and the primary IP address is 192.168.2.1 you use ifconfig as follows:

This adds two virtual interfaces with IP address 192.168.2.2 and 192.168.2.3.  The interface number must be unique for each interface (for example eth0:1, eth0:2 etc).

Configuring Virtual IP Address in Solaris

For example if you network interface is hme0 and the primary IP address is 192.168.2.1 you use ifconfig as follows:

This adds two virtual interfaces with IP address 192.168.2.2 and 192.168.2.3.  The interface number must be unique for each interface (for example hme:1, hme:2 etc).

Using IP Pool Tasks

IPPoolInitTask

The IPPoolInitTask is only executed once per load test session and creates the pool with addresses.

The pool can be initialized in two ways:

1. A specified range of addresses
2. By probing the specified interface(s)

An example where the pool is initiated from a range:

The range creates IP addresses 192.68.2.1 to 192.68.2.100, excluding all addresses ending with 0. The "Shuffle" option is used to ensure that the generated numbers are not stored in the pool ordered.

The range can be specified in several ways:

Another example, where the pool is generated by probing the interface (in this case the physical interfaces e100g0,  e100g1 and e100g3):

Here we exclude all addresses ending with ".1".

PoolGetTask

To get next available task from the IP pool, the PoolGetTask is used:

As Pool Name we specify the name of the IP pool created by IPPoolInitTask. We assign the retrieved IP address to the variable "ip". This variable can then be used in other task where we need to specify the local IP Address.

PoolReturnTask

When we do not need the IP Address retrieved by PoolGetTask, we must return it to the pool using PoolReturnTask: