Specifications

Chapter 6
6-10
To clarify how this differs from default behavior, contrast the basic behavior
of a BIG-IP in the following description. Each of the two BIG-IP units in a
redundant system has a built-in tendency to try to become the active unit.
Each unit attempts to become the active unit at boot time; if you boot two
BIG-IP units at the same time, the one that becomes the active unit is the
one that boots up first. In a redundant configuration, if the BIG-IP units are
not configured with a preference for being the active or standby unit, either
unit can become the active unit by becoming active first.
The active or standby preference for the BIG-IP is defined by setting the
appropriate startup parameters for the fail-over mechanism in BIG/db. For
more details on fail-over startup and functioning, see Failover and cluster
keys, on page 9-2.
To force a BIG-IP to active or standby state
The following example shows how to set the BIG-IP to standby:
b db set Local.Bigip.Failover.ForceStandby
b failover init
A BIG-IP that prefers to be standby can still become the active unit if it does
not detect an active unit.
This example shows how to set a BIG-IP to active:
b db set Local.Bigip.Failover.ForceActive
b failover init
A BIG-IP that prefers to be active can still serve as the standby unit when it
is on a live redundant system that already has an active unit. For example, if
an active BIG-IP that preferred to be active failed over and was taken out of
service for repair, it could then go back into service as the standby unit until
the next time the redundant system needed an active unit, for example, at
reboot.
Setting up active-active redundant BIG-IP units
You can use the active-active feature to simultaneously load balance traffic
for different virtual addresses on BIG-IP redundant systems. Performance
improves when both BIG-IP units are in active service at the same time. In
active-active mode, you configure virtual servers to be served by one of the
two units. If one unit fails, the remaining BIG-IP assumes the virtual servers
of the failed machine. For this configuration to work, each BIG-IP must
have its own unit ID number. Each virtual server, NAT, or SNAT that you
create includes a unit number designation that determines which active unit
handles its connections.
Note
If you do not want to use this feature, BIG-IP redundant units operate in
active/standby mode by default.