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Manual Chapter: BIG-IP Local Traffic Manager version 9.3 Implementations: Setting up a One-IP Network Topology
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16

Setting up a One-IP Network Topology


Introducing the one-IP network topology

Another configuration option you can use with the BIG-IP® system is a one-IP network topology. This differs from the typical two-network configuration in two ways:

  • Because there is only one physical network, this configuration does not require more than one interface on the BIG-IP system.
  • Clients need to be assigned SNATs to allow them to make connections to servers on the network in a load balancing pool.

The single interface configuration is shown in Figure 16.1 .

 

Figure 16.1 An example of a single interface topology

To set up this configuration, you need to complete the following tasks on the BIG-IP system:

  • Create a load balancing pool for the content servers.
  • Create a virtual server to load balance traffic to the content server pool.
  • Define a default route for the external VLAN.
  • Configure a SNAT for the client.

Creating a pool for a one-IP network topology

The first task required to set up this solution is to create a pool that contains the content servers that you want to load balance. Before creating the pool, verify that all content servers for the pool are in the network of VLAN external.

To create a pool

  1. On the Main tab of the navigation pane, expand Local Traffic, and click Pools.
    The Pools screen opens.
  2. In the upper-right corner of the screen, click Create.
    The New Pool screen opens.
  3. Note: If the Create button is unavailable, this indicates that your user role does not grant you permission to create a pool.
  4. From the Configuration list, select Advanced.
  5. In the Name box, type a name for the pool, such as server_pool.
  6. For the Health Monitors setting, from the Available box select http, and click the Move button (<<) to move the monitor name to the Active box.
  7. For the Allow SNAT setting, verify that the value is Yes.
  8. For the remaining settings in the Configuration area of the screen, retain the default values.
  9. In the Resources area of the screen, use the default values for the Load Balancing Method and Priority Group Activation settings.
  10. For the New Members setting, add the pool members:
    1. Click the New Address option.
    2. In the Address box, type the IP address of a server in the pool.
    3. In the Service Port box, type 80, or select HTTP.
    4. Click Add.
    5. Repeat steps b, c, and d for each server in the pool.
  11. Click Finished.

Creating a virtual server

The second task required to set up this solution is to create a virtual server that references the pool of servers that you want to load balance. The pool that the virtual server references is the pool you created in the previous step.

To create a virtual server

  1. On the Main tab of the navigation pane, expand Local Traffic, and click Virtual Servers.
    The Virtual Servers screen opens.
  2. In the upper-right corner of the screen, click Create.
    The New Virtual Server screen opens.
  3. Note: If the Create button is unavailable, this indicates that your user role does not grant you permission to create a virtual server.
  4. In the Name box, type a name for the virtual server, such as vs_one_ip.
  5. For the Destination setting:
    1. Verify that the type of virtual server is Host
    2. In the Address box, type an IP address for the virtual server.
  6. In the Service Port box, type 80, or select HTTP from the list.
  7. In the Configuration area of the screen, retain the value of the Protocol setting, TCP.
  8. From the HTTP Profile list, select http.
    This assigns the default HTTP profile to the virtual server.
  9. In the Resources area of the screen, locate the Default Pool setting and select the name of the pool you created in the previous section (using our example, this would be server_pool).
  10. Click Finished.

Defining a default route

Another task that you must perform to implement one-IP network load balancing is to define a default route for the VLAN external.

To define a default route

  1. On the Main tab of the navigation pane, expand Network and click Routes.
    The Routes screen opens.
  2. In the upper-right corner of the screen, click Add.
    The New Route screen opens.
  3. For the Type setting, verify that it is set to Default Gateway.
    This disables the Destination and Netmask settings.
  4. For the Resource setting:
    1. From the list on the left, select Use VLAN.
    2. From the list on the right, select external.
  5. Click Finished.

Configuring a client SNAT

Finally, configure the BIG-IP system to handle connections originating from the client. You must define a SNAT in order to change the source address on the packet to the SNAT external address, which is located on the BIG-IP system. Otherwise, if the source address of the returning packet is the IP address of the content server, the client does not recognize the packet because the client sent its packets to the IP address of the virtual server, not the content server.

If you do not define a SNAT, the server returns the packets directly to the client without giving the BIG-IP system the opportunity to translate the source address from the server address back to the virtual server. If this happens, the client might reject the packet as unrecognizable.

To configure a client SNAT

  1. On the Main tab of the navigation pane, expand Local Traffic, and click SNATs.
    The SNATs screen opens.
  2. In the upper-right corner of the screen, click Create.
    The New SNAT screen opens.
  3. In the Name box, type a name for the SNAT, such as snat_one_ip.
  4. In the Translation box, type an IP address that you want to use as a translation IP address.
  5. From the Origin list, select Address List.
    This displays additional configuration settings.
  6. For the Address List setting:
    1. For the Type setting, verify that Host is enabled.
    2. In the Address box, type a client IP address.
    3. Click Add.
    4. Repeat this process for each client to which you want to assign the translation address.
  7. From the VLAN Traffic list, select Enabled on.
  8. For the VLAN List setting, from the Available box select external, and click the Move button (<<) to move the VLAN name to the Active box.
  9. Click Finished.


 

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