Wireless/Redundant Edge Services xl Module Management and Configuration Guide WS.02.xx and greater

10-5
Redundancy Groups
High Availability for Wireless Services
■ Standby mode—In standby mode, the module is primarily responsible
for providing failover capabilities if a module in active mode becomes
unavailable. (A module in standby mode can adopt RPs in the circum-
stances described in “Adopting RPs” on page 10-5.)
Both Wireless Edge Services xl Modules and Redundant Wireless Services xl
Modules support both modes. This difference between primary and redundant
modules lies in the redundant module’s lack of RP licenses, not in the modes
in which the modules function. For example, in a group that includes one
primary module and two redundant modules, you can configure the primary
module in active mode and the redundant modules in standby mode. But you
can also choose to configure all three modules in active mode. In fact, this is
often a good idea because the active modules load balance RPs between them,
adding capacity to the network.
Note Selecting active mode for more than one module in a redundancy group still
provides high availability. If one module fails, another active module will adopt
the failed module’s radio ports.
Adopting RPs
How a Wireless Edge Services xl Module or Redundant Wireless Services xl
Module adopts RPs depends on the module’s mode.
Adopting RPs in Active Mode
All active members of a redundancy group can adopt RPs. By default, the
modules load balance the available RPs based on each module’s load value.
When an RP is detected, the active module with the lowest load value adopts
that RP. If more than one module has the same load value, the module with
the lowest media access control (MAC) address adopts the RP. The load value
is based on the number of RPs adopted by the module, not on the amount of
traffic the RPs support.
Basing adoption on the load value is not always the best way to manage RPs,
however. Sometimes, you may want manual control over which RPs are
adopted by which module. See “Setting up Adoption Preference IDs to Control
RP Adoption” on page 10-24 to learn how to use adoption preference IDs to
determine which RPs each module adopts.