WESM zl Management and Configuration Guide WT.01.28 and greater

1-74
Introduction
Redundancy Groups
Redundancy Group Operation Modes
Group members can operate in either active mode or standby mode. The type of
module (primary or redundant) has no relation to the operation mode. You can place
a primary module in standby mode, or more typically, you can place a redundant
module in active mode. An active redundant module adds capacity by loading
balancing RPs with other members of the group. (Remember it does not add capacity
by increasing the number of RPs that can be adopted.)
An active member can adopt RPs at any time. If a group has more than one active
member, together the active members can adopt as many RPs as allowed by the group
authorization level (see “Rules of Redundancy Groups” on page 1-73.)
Like active members, standby members adopt RPs using any available group RP
licenses. However, a standby member can adopt RPs only when:
■ it does not receive heartbeats from the active member for too long a period
■ the active member fails to adopt an RP
Thus, when necessary, one of the standby members can assume the active module’s
services, and wireless services continue after a minimum of delay.
Table 1-8 describes some of the situations in which a standby member adopts RPs.
Table 1-8. Situations in Which a Standby Member Adopts RPs
Figure 1-25 illustrates a situation in which a standby member adopts RPs.
Situation Possible Causes
The standby member does not
receive heartbeats from any one
of the active members.
• The active member has failed.
• The wireless services-enabled switch in which the
active member is installed has failed.
• A failed network connection has isolated the active
member from the rest of the network.
All active members fail to adopt an
RP.
• The active member’s internal downlink port has not
been tagged for the Radio Port VLAN.
• The network infrastructure does not support the Radio
Port VLAN on all interfaces between the RP and the
active member.
• The active member is explicitly prohibited from
adopting the RP.