LB::reselect

Description

This command is used to advance to the next available node in a pool, either using the load balancing settings of that pool, or by specifying a member explicitly. Note that the reselect may not happen immediately; it may wait until the current iRule event is completely finished executing.

Warning

Up to BIG-IP 13.0.x and 12.1.3.5, there was no reselect retry limit built into the command: You MUST implement a limiting mechanism in your iRule using logic similar to that in the examples below. For more information, refer to AskF5 SOL10386 and Bug ID 656898

Syntax

LB::reselect
LB::reselect nexthop <IP address>
LB::reselect node <node_ip_address> <node_port>
LB::reselect pool <pool_name> [member <member> [<port>]]
LB::reselect pool <pool_name> [member <member>:<port>]
LB::reselect rateclass <rateclass name>
LB::reselect virtual <virtual server name>
LB::reselect vlan <vlan name>

LB::reselect

  • Selects the next available member in the current pool, based on pool Load Balancing options

LB::reselect nexthop <IP address>

  • Selects the MAC address for the selected IP address as the nexthop
  • See nexthop for possible additional options

LB::reselect pool <pool_name> [member <member> [<port>]]

  • Selects the specified member from the specified pool

LB::reselect pool <pool_name> [member <member>:<port>]

  • Selects the specified member from the specified pool

LB::reselect rateclass <rateclass name>

  • Selects the specified rate class

LB::reselect virtual <virtual server name>

  • Selects the specified virtual server

LB::reselect vlan <vlan name>

  • Selects the specified VLAN

Examples

when CLIENT_ACCEPTED {
  set def_pool [LB::server pool]
  set lb_fails 0
}
when LB_FAILED {
  if { $lb_fails < [active_members $def_pool] } {
    LB::mode rr
    LB::reselect pool $def_pool
  } else {
    ... add failure logic here
  }
  incr lb_fails
}

when CLIENT_ACCEPTED {
  set def_pool [LB::server pool]
  set lb_fails 0
}
when LB_SELECTED {
  if { $lb_fails < [active_members $def_pool] } {
    LB::mode rr
    LB::reselect pool $def_pool
  }
  incr lb_fails
}

Version Specific Notes

LTM 9.2 When load balancing fails to a selected member, the iRule LB::reselect command repeatedly attempts to connect to the unavailable member, rather than selecting the next available pool member. See AskF5 SOL8188 (CR84102) (deb)
LTM 9.3, 9.4, & 9.3.1 When load balancing fails to a selected member, the iRule LB::reselect command repeatedly attempts to connect to the unavailable member, rather than selecting the next available pool member. See AskF5 SOL8188 (CR85186) (deb)
LTM 9.0 - 9.4.4 SOL8724 - Use of LB::detach and LB::reselect within an LB_FAILED event causes a system crash - deb (31 Oct 2008)
LTM 9.4.5 SOL9278 - Using iRules LB::detach command then selecting a new load balancing target may stall connection - deb (31 Oct 2008)

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