Clicking the Add New button brings you to the following screen where the properties of the Real Server are set.

Allow Remote Addresses: By default only Real Servers on local networks can be assigned to a Virtual Service. Enabling this option will allow a non-local Real Server to be assigned to the Virtual Service. This option is enabled by default.

Note: To make the Allow Remote Addresses option visible, Enable Non-Local Real Servers must be selected (in System Configuration > Miscellaneous Options > Network Options). Also, Transparency must be disabled in the Virtual Service.
Note: When alternative gateways/non-local Real Servers are set up, health checks are routed through the default gateway.

Real Server Address: The Real Server address. This can either be an IP address or a Fully Qualified Domain Name (FQDN). This is not editable when modifying a Real Server. An FQDN can only be used if a Nameserver is configured. The resolved name is listed next to the IP address in parenthesis. For further information, refer to the Host & DNS Configuration section. If an FQDN is used when adding a Real Server – the name is resolved at the time of adding. If it fails to resolve, the Real Server is not created and an error is generated.

You can either type the address of a new Real Server, or select an existing Real Server from the drop-down list provided. The entries before the line in the drop-down list are existing Real Servers. The entries below the line are auto-complete form options. Real Servers already added to this SubVS are not listed in the drop-down list.

Note: This drop-down list does not appear on Safari browsers due to a browser limitation.

Add to all SubVSs

When adding a Real Server to a SubVS, a check box is available that, when selected, adds the Real Server to all SubVSs in that Virtual Service.

Port: The forwarding port of the Real Server. This field is editable, so the port may be altered later if required.

Forwarding Method: Either NAT (Network Address Translation) or Route (Direct) forwarding. The available options are dependent on the other modes selected for the service.

Weight: The Real Server's weight. This is weight of the Real Server, as used by the Weighted Round Robin, Weighted Least Connection and Adaptive scheduling methods. The default initial value for the weight is 1000, the maximum is 65535, and the minimum is 1. It is a good benchmark to give a Real Server a weight relative to its processor speed, for example, if server1 seems to bring four times the power of server2, assign a weight of 4000 to server1 and weight of 1000 to server2.

Connection Limit: The maximum number of open connections that a Real Server will accept before it is taken out of the rotation. This is only available for Layer 7 traffic. The limit stops new connections from being created, but it will allow requests that already have persistent connections to the server. Persistent connections include connections to a Virtual Service using Session Broker Persistence which include a Session Broker cookie as set by the Connection Broker.

A maximum number of 1024 Real Servers is allowed. This is the global limit and is divided among the existing Virtual Services. For example, if one Virtual Service had 1000 Real Servers, then the remaining Virtual Services can only have 24 further Real Servers in total.

Note: For the LoadMaster Exchange, there is a limit of six Real Servers that may be configured.

Click the Add This Real Server button and it gets added to the pool.

Connection Rate Limit

As of LoadMaster firmware version 7.2.51, there is a Connection Rate Limit field when configuring a Real Server. This allows you to set the maximum number of open Connections Per Second (CPS) that can be sent to a Real Server before it is taken out of rotation. The maximum limit is 100000 (100,000 CPS). If the Connection Rate Limit is set to 0 (the default) the feature is disabled, that is, there is no rate limiting.

If rate limiting is enabled, the LoadMaster limits the number of new connections going to a particular Real Server. If the limit is reached, the Real Server is taken out of rotation/selection (that is, removed from the load balancing scheduling algorithm) until the current period is finished. The 'rate limit period' is 0.1 seconds. Any value less than 10 CPS is handled like 10 CPS.

When a Real Server is taken out of rotation, the current connection will then be scheduled to go to a different Real Server in the Virtual Service (or SubVS). This includes new connections with persistence settings to the rate-limited Real Server - these are also sent to another Real Server when the rate limit is exceeded. If no Real Servers are found, the usual rejection methods are used.

No new connections are sent to the rate-limited Real Server until the current 'rate limit period' expires and the Real Server is returned to the load balancing scheduling process.

The rate value for the Real Server also takes slow start into consideration. At Real Server restart, the CPS limit will get to its full value at the end of the slow start period. For further details on the slow start feature, refer to the heading Least Connection Slow Start under section L7 Configuration

Critical

Note: This option will only appear if the Enhanced Options check box is enabled. For further information on the Enhanced Options check box, refer to the Real Servers section.

In the Real Servers section of the Virtual Service modify screen, there is a Critical check box for each of the Real Servers. Enabling this option indicates that the Real Server is required for the Virtual Service to be considered available. The Virtual Service is marked as down if the Real Server has failed or is disabled.

If a Real Server on a SubVS is marked as critical – the SubVS is marked as down if that Real Server is down. However, the parent Virtual Service will not be marked down unless that SubVS is marked as critical.

Note: This option overrides the Minimum number of RS required for VS to be considered up field. For example, if the minimum is set to two and only one Real Server is down but that Real Server is set to critical – the Virtual Service is marked as down.

In all cases, if the Virtual Service is considered to be down and the Virtual Service has a sorry server or an error message configured, these are used.

Healthcheck On

Note: This option will only appear if the Enhanced Options check box is enabled. For further information on the Enhanced Options check box, refer to the Real Servers section.

In the Real Servers section of the Virtual Service modify screen, there is a Healthcheck On drop-down list for each of the Real Servers. This allows you to specify what Real Server the health check is based on. This can either be set to Self to perform the health check based on that particular Real Server status, or another Real Server can be selected. For example – if Real Server 1 is down, any Real Servers which have their health check based on Real Server 1 will also be marked as down, regardless of their actual Real Server status.

Some points to be aware of are listed below:

  • A Real Server can only follow a Real Server and not a SubVS.
  • A Real Server can follow a Real Server that is also following a third Real Server. The status of the first two Real Servers will reflect the status of the third Real Server.
  • Chains of Real Servers are allowed – but loops are not allowed and cannot be created.
  • If a Real Server is deleted (either singly or as part of a Virtual Service), all Real Servers that are following the Real Server are reset to normal behaviour (that is, they will start using the Virtual Service health check options).
  • If all Real Servers in a Virtual Service are following Real Servers on a different Virtual Service, the health check parameters for the Virtual Service are not shown on the WUI (because the settings do not affect any Real Servers).
  • Disabling the Enhanced Options check box will disable all Real Server health check following for that Virtual Service.