ILB Features

The key features of ILB include:

• Supports stateless Direct Server Return (DSR) and Network Address Translation (NAT) modes of operation for IPv4 and IPv6

• Enables ILB administration through a command-line interface (CLI)

• Provides server monitoring capabilities through health checks

The following list describes the additional features of ILB:

• Enables clients to ping virtual IP (VIP) addresses – ILB can respond to Internet Control Message Protocol (ICMP) echo requests to IP address of virtual service from clients. ILB provides this capability for DSR and NAT modes of operation.

• Enables you to add and remove servers from a server group without interrupting service – You can dynamically add and remove servers from a server group, without interrupting existing connections established with the back-end servers. ILB provides this capability for the NAT mode of operation.

• Enables you to configure session persistence (stickiness) – For many applications, it is important that a series of connections, packets, or both, from the same client are sent to the same back-end server. You can configure session persistence (that is, source address persistence) for a virtual service by using the -p option and specifying the pmask in the subcommand ilbadm create-rule. For more information, see How to Create an ILB Rule. After a persistent mapping is created, subsequent requests for connections, packets, or both, to a virtual service with a matching source IP address of the client are forwarded to the same back-end server. The prefix length in Classless Inter-Domain Routing (CIDR) notation is a value between 0-32 for IPv4 and 0-128 for IPv6. The support for session persistence is available for DSR and NAT modes of operation.

• Enables you to perform connection draining – ILB provides support for this capability only for servers of NAT-based virtual services. This capability prevents new connections from being sent to a server that is disabled. This feature is useful for shutting down the servers without disrupting the active connections or sessions. Existing connections to the server continue to function. After all the connections to that server terminate, the server can then be shut down for maintenance. After the server is ready to handle requests, the server is enabled so that the load balancer can forward new connections to it. This feature enables you to shut down servers for maintenance without disrupting active connections or sessions.

• Enables load-balancing of TCP and UDP ports – ILB can load balance all ports on a given IP address across different sets of servers without requiring you to set up explicit rules for each port. ILB provides this capability for DSR and NAT modes of operation.

• Enables you to specify independent ports for virtual services within the same server group – With this feature, you can specify different destination ports for different servers in the same server group for the NAT mode of operation.

• Enables you to load balance a simple port range – ILB can load balance a range of ports on the VIP to a given server group. For convenience, you can conserve IP addresses by load-balancing different port ranges on the same VIP to different sets of back-end servers. Also, when session persistence is enabled for NAT mode, ILB sends requests from the same client IP address for different ports in the range to the same back-end server.

• Enables port range shifting and collapsing – Port range shifting and collapsing depend on the port range of a server in a load-balancing rule. So, if the port range of a server is different from the VIP port range, port shifting is automatically implemented. If the server port range is a single port, then port collapsing is implemented. These features are provided for the NAT mode of operation.