Link Load Balancing : Configuring a link group
 
Configuring a link group
Link groups include ISP gateways your company uses for outbound traffic. Grouping links reduces the risk of outages and provisions additional bandwidth to relieve potential traffic congestion. See “Using link groups”.
The link group configuration specifies the load balancing algorithm and the gateway routers in the load balancing pool. You can enable LLB options, such as persistence rules and proximity routes.
Before you begin:
• You must have configured gateway links and persistence rules and before you can select them in the link group configuration.
• You must have Read-Write permission for Link Load Balance settings.
After you have configured a link group configuration object, you can select it in the link policy configuration.
To configure a link group:
1. Go to Link Load Balance > Link Group.
The configuration page displays the Link Group tab.
2. Click Add to display the configuration editor.
3. Complete the configuration and add members as described in Table 24.
4. Save the configuration.
 
Table 24: Link group configuration
Settings
Guidelines
Route Method
• Weighted Round Robin—Dispatches new connections to link members using a weighted round-robin method.
• Least Connections—Dispatches new connections to the link member with the lowest number of connections.
• Least New Connections per Second—Dispatches new connections to the link member that has the lowest rate of new connections per second.
• Least Throughput Outbound—Dispatches new connections to the link member with the least outbound traffic.
• Least Throughput Inbound—Dispatches new connections to the link member with the least inbound traffic.
• Least Throughput Total—Dispatches new connections to the link member with the least total traffic (that is, inbound plus outbound).
• Spillover Throughput Outbound—Dispatches new connections according to the spillover list based on outbound traffic.
• Spillover Throughput Inbound—Spillover list based on inbound traffic.
• Spillover Throughput Total—Spillover list based on total traffic (that is, inbound plus outbound).
• Source Address Hash—Selects the gateway link based on a hash of the source IP address.
Persistence
Select a persistence configuration. Optional.
Proximity Route
• Enable—The system uses the proximity route logic and configuration when determining routes.
• Disable—The system does not use the proximity route configuration.
Add member
Name
Unique name. No spaces or special characters.
After you initially save the configuration, you cannot edit the name.
Gateway
Select a gateway configuration object. See “Configuring gateway links”.
Weight
Assigns relative preference among members—higher values are more preferred and are assigned connections more frequently. The default is 1. The valid range is 1 to 256.
All load balancing methods consider weight, except spillover, which uses its own priority configuration. Servers are dispatched requests proportional to their weight, relative to the sum of all weights.
The following example shows the effect of weight on WRR:
Sever A, Weight 2; Server B, Weight 1: Requests are sent AABAAB.
Sever A, Weight 3; Server B, Weight 2: Requests are sent AABAB.
For other methods, weight functions as a tie-breaker. For example, with the Least Connection algorithm, requests are sent to the server with the least connections. If the number of connections is equal, the request is sent to the server with the greater weight. For example:
Server A, Weight 1, 1 connection
Server B, Weight 2, 1 connection
The next request is sent to Server B.
Spillover Priority
Assigns a priority to the link when using a spillover load balancing method. Higher values have greater priority. When a spillover method is enabled, the system dispatches new connections to the link that has the greatest spillover priority until its threshold is exceeded; then it dispatches new connections to the link with the next greatest priority until its threshold is exceeded, and so on.
If multiple links in a link group have the same spillover priority, the system dispatches new connections among those links according to round robin.
The default is 0. The valid range is 0-9.
Status
• Enable—The member is considered available for new traffic.
• Disable—The member is considered unavailable for new traffic.