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Manual Chapter: Configuration Guide for the BIG-IP® Link Controller: Bandwidth Load Balancing
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12

Bandwidth Load Balancing


Introducing bandwidth load balancing

The Link Controller provides you with a variety of methods of managing the traffic flowing in and out of your network. A common method is bandwidth load balancing. In bandwidth load balancing, you instruct the Link Controller to use a specific link until a traffic threshold has been met. After that threshold is met, the Link Controller shifts traffic to another link. When the traffic falls below the threshold, the Link Controller shifts traffic back to the first link.

You can configure three different types of bandwidth settings for each link:

  • Inbound, which refers to the amount of traffic flowing into the network
  • Outbound, which refers to the amount of traffic flowing out of the network
  • Total, which refers to the cumulative amount of traffic flowing in and out of the network

To illustrate how bandwidth load balancing works, consider the fictional company SiteRequest. This company has two links for managing its inbound and outbound traffic:

  • Link Alpha, which is the primary link for the network. This link uses an ISP that can handle up to 20Mbps of total (both inbound and outbound) traffic.
  • Link Beta, which is a secondary link for the network. This link uses an ISP that can handle 10Mbps of total traffic. This link is intended to be used only when Link Alpha has reached its maximum traffic capacity.

With the Link Controller, the IT department at SiteRequest configures the network traffic to flow through Link Alpha until the bandwidth threshold reaches 20Mbps. When the traffic on Link Alpha exceeds that threshold, the Link Controller automatically switches to Link Beta, until the traffic on Link Alpha falls below 20Mbps again. This configuration helps ensure that network traffic for SiteRequest flows in a cost-effective manner.

The following sections describe how to configure a Link Controller that employs bandwidth load balancing to balance traffic across multiple links.

Note

This type of configuration assumes that you have completed the base configuration created by the Setup utility. For more information, see the Configuration Guide for Local Traffic Management. To use this configuration, you must configure at least three VLANs when you create the initial configuration: one VLAN for each ISP, and one VLAN for the internal network.
The IP addresses used in this example are for demonstration only. You should substitute IP addresses appropriate for your network.

Configuring bandwidth load balancing

When you set up bandwidth load balancing, you have several tasks to complete on the Link Controller:

  • Configure the links
    The first step to bandwidth load balancing is adding the links to your Link Controller configuration and assigning bandwidth values to each of these links.
  • Create and implement the default gateway pool
    You must create the default_gateway_pool to provide the information the Link Controller needs about which links it can load balance network traffic.
  • Configure virtual servers
    You need to configure a virtual server in the network of the link for each ISP to load balance inbound connections across the servers. You also configure one wildcard virtual server (0.0.0.0:0) to load balance outbound connections across the routers.
  • Add a wide IP for inbound load balancing
    Add a wide IP to handle inbound DNS requests for each pair of virtual servers you add for each link.
  • Configuring transparent monitors
    These monitors determine whether a given Internet resource is accessible through a specific link on your network.

Configuring the links

The first step in designing a Link Controller configuration that uses bandwidth load balancing to manage outbound traffic is to add and configure the links into the Link Controller. You can configure each link using a variety of options; however, the critical settings are the Inbound Traffic, Outbound Traffic, and Total Traffic options, with which you set the bandwidth thresholds for the link.

To add a link for use with bandwidth load balancing

  1. On the Main tab of the navigation pane, expand Link Controller, and then click Links.
    The main link screen opens.
  2. Click the Create button.
    The New Link screen opens.
  3. In the Name box, type a name for the link.
  4. In the Router Address box, type the IP address to associate with the link.
  5. In the Uplink Address box, type the IP address to associate with the Internet Service Provider to which outgoing traffic is sent.
  6. In the Service Provider box, type the name of the Internet Service Provider.
  7. From the Configuration list, select Advanced.
    An additional set of configuration options open.
  8. In the Traffic Limits section, assign the appropriate values for any combination of the Inbound, Outbound, and Total settings.
    Each of these settings allows you to select one of two choices: None or Up to.
    • If you select None, the Link Controller ignores that statistic when load balancing traffic.
    • If you select Up to, a box appears, in which you can define the bandwidth threshold in bits-per-second (bps).
  9. Click the Create button to save your changes.

Creating the default gateway pool

After you have added and configured the relevant links, the next step in implementing bandwidth load balancing is to create the default gateway pool that will load balance the traffic across the links.

To create a default gateway pool

  1. On the Main tab of the navigation pane, expand Local Traffic and then click Pools.
    The main pools screen appears.
  2. Click the Create button.
    The create pool screen appears.
  3. In the Name box, type the name of the pool.
    We recommend that you use a name such as default_gateway_pool.
  4. In the New Members section, add the IP addresses associated with each link to locate and add the links to the pool.
  5. Configure additional options for the pool as needed.
    Advanced options for pools is available when you select Advanced from the Configuration list.
  6. Click Finished to save your changes.

Implementing the default gateway pool

After you create a default gateway pool, you must instruct the Link Controller to use the pool as the default gateway connection between the internal network and the Internet.

To implement the default gateway pool

  1. On the Main tab of the navigation pane, expand Network and then click Routes.
    The main routes screen opens.
  2. Click the Add button.
    The add route page opens.
  3. From the Type list, select Default Gateway.
  4. From the Resource section, select Use Pool.
    A list appears, allowing you to select the pool of links.
  5. Select the pool name that represents the group of links you want to use as the default gateway pool.
  6. Click Finished to save your changes.

Defining the virtual servers for an additional Internet connection

After you create the pools, you configure the virtual servers, one for each link that load balances inbound connections across the servers. You also configure one wildcard virtual server to load balance outbound connections across the routers.

To add a virtual server

  1. On the Main tab of the navigation pane, expand Local Traffic and then click Virtual Servers.
    The main screen for virtual servers appears.
  2. Click the Create button.
    The New Virtual Server screen opens.
  3. In the Name box, type the name of the virtual server.
  4. Define the destination of the virtual server.
    1. Select the appropriate destination type: if the virtual server represents a single resource select Host, if the virtual server represents a group of resources, select Network from the Destination section.
    2. In the Address box, type the IP address of the virtual server.
  5. In the Service Port option, type the port number that the virtual server uses.
    Alternatively, you can select a port from the list. For example, if you select HTTP from the list, the corresponding box automatically updates to contain the corresponding port number, 80.
  6. Configure the remaining properties associated with this virtual server as needed.
  7. Click the Finished button to save the new virtual server configuration.

To define a wildcard virtual server for outbound traffic

  1. On the Main tab of the navigation pane, expand Local Traffic and then click Virtual Servers.
    The main screen for virtual servers appears.
  2. Click the Create button.
    The New Virtual Server screen opens.
  3. For a wildcard virtual server, use the following settings:
    • For the name, type outbound.
    • For the destination address, type 0.0.0.0.
    • For the service, type 0 or select any from the list.
  4. In the VLAN Traffic option, select the VLANs on which you want to enable this wildcard virtual server.
    You will likely want to enable this virtual server for only one matching VLAN.
  5. Click the Finished button to apply your changes.

Adding a wide IP for inbound load balancing

To complete the link load balancing configuration, you must configure a wide IP for each pair of virtual servers you created for each link. Each wide IP in your configuration has a set of virtual servers that the Link Controller load balances incoming DNS requests to. The wide IP is made up of only virtual servers managed by the Link Controller. When you configure the wide IP, you specify the load balancing methods that the Link Controller applies to the incoming DNS requests.

To add a wide IP

  1. On the Main tab of the navigation pane, expand Link Controller and then click Inbound Wide IPs.
    The main wide IP screen opens.
  2. Click the Create button.
    The New Wide IP screen opens.
  3. In the Name box, type a name that identifies the wide IP.
  4. In the TTL box, type the time-to-live value you want to associate with this wide IP.
  5. From the Load Balancing list, select the appropriate load balancing modes.
    You can select a load balancing mode at three different levels: Preferred, Alternate, and Fallback. These modes are described in detail in Chapter 9, Inbound Load Balancing .
  6. In the Fallback IP box, type the IP address that the Link Controller uses when it cannot load balance inbound traffic.
  7. In the Virtual Server section, add the virtual servers that belong to this wide IP.
  8. Click the Finished button to save the new wide IP.

Configuring transparent monitors for the links

When you create the default gateway pool, the Link Controller automatically creates simple ICMP monitors that check to make sure the IP addresses in the default gateway pool are available to the Link Controller. In addition to the default ICMP monitors, you can configure transparent monitors that verify the path taken by traffic through each link. You can use these transparent monitors to check the availability of a device in an ISP network or on the Internet.

When you configure a transparent monitor for a link, you must accomplish two tasks:

  • Create a transparent monitor
  • Add the monitor to the link

Creating transparent monitors

The Link Controller supports a wide variety of monitor types. You can use these types to create a custom monitor that probes for specific data on the network. For example, you can create a custom monitor based on the HTTP monitor type that queries a resource for specific information on a Web page. If the monitor can access that page, the Link Controller considers the resource to be available.

In most situations, a monitor is designed to track the availability of the resource to which it is assigned. In the case of links, however, you often want to monitor the availability of a resource on the other side of the link, as opposed to the link itself. These types of monitors are referred to as transparent monitors. A transparent monitor is any monitor assigned to a resource that verifies the availability of another resource.

As an example of how transparent monitors work, consider the fictional company SiteRequest. This company uses a fictional company, Global ISP, as one of its Internet Service Providers. To ensure that a link installed at Site Request can access Global ISP, the IT department creates a custom monitor based on the ICMP monitor type and assigns that monitor to the link. This monitor then attempts to use the link to connect to Global ISP. If the connection is successful, the monitor reports that the link is available.

To create a custom monitor using the transparency option

  1. On the Main tab of the navigation pane, expand Link Controller and then click Monitors.
    The monitors screen opens.
  2. Click the Create button.
    The create monitor screen opens.
  3. In the Name box, type a name for the monitor.
  4. For the Type setting, select the type of monitor that you want to create.
    If a monitor of that type already exists, Import Settings appears.
  5. From the Configuration list, select Advanced. This allows you to modify additional default settings.
  6. In the Transparent section, select Yes.
  7. In the Alias Address box, type the IP address of the resource that you want the monitor to probe.
  8. Click the Finished to save your changes.

Adding monitors to links

After you create a transparent monitor, you must add it to the link.

To add a monitor to a link

  1. On the Main tab of the navigation pane, expand Link Controller and then click Links.
    The main link screen opens.
  2. Click the link to which you want to assign a monitor.
    The properties screen for the link opens.
  3. Select the transparent health monitors that you apply for this link.
    To select a transparent monitor, click the name of the monitor from the Available list within the Health Monitors area, then use the Move button [<<] to add the monitor to the Active list. We recommend that you add at least the bigip_link and snmp_link monitors.
  4. Click the Finished button to save your changes.



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