WESM zl Management and Configuration Guide WT.01.28 and greater

10-13
Redundancy Groups
Configuring a Redundancy Group
3. In the Redundancy Group ID field, enter a number for the group. Each redundancy
group on your network must have a unique group ID, and you must use the same
group ID for each member of the group. You can enter any number from 1
through 65535.
4. Choose the Mode:
• Select Active to allow the module to adopt RPs in all circumstances (as long
as the group has sufficient licenses).
• Select Standby to allow the module to adopt RPs only when active members
fail to do so.
More than one member of the group can act in active mode, and more than one
can act in standby. You can choose either mode for either model (the Wireless
Edge Services zl Module or the Redundant Wireless Services zl Module). See
“Active or Standby Mode” on page 10-4 and “Adopting RPs” on page 10-5 for
more information on the effects of the mode.
5. In the Discovery Period field, accept the default setting of 30 seconds, or enter
a number from 10 through 60 seconds. (The discovery period is the amount of
time that the module spends locating the other modules and ensuring that they
are using the same redundancy group configuration.)
6. In the Heartbeat Period field, accept the default setting of 5 seconds, or enter a
number from 1 through 255 seconds. Each module in the redundancy group
periodically sends a heartbeat to determine if the other modules are still “alive,”
or available. This setting determines the number of seconds between each
heartbeat.
7. In the Hold Period field, accept the default setting of 15 seconds, or enter a
number from 1 through 255 seconds. This setting determines the number of
seconds that the module waits when it does not receive a heartbeat from another
module in the redundancy group. If no heartbeats are received for the number
of seconds specified in the hold period, the module determines that the other
module in the group is unavailable. If the active member is unavailable, a standby
member takes over its responsibilities and begins to adopt RPs.
As a general rule, you should configure the hold period to be three times as long
as the heartbeat period. In practice, this means that if a module does not receive
three consecutive heartbeats, it decides that the other module is unreachable.
8. Check the Handle STP convergence box if you want the module to factor in
Spanning Tree Protocol (STP) convergence time before trying to establish the
redundancy group.
STP’s relatively slow convergence can cause a problem when one member of a
group is in a subnetwork that uses STP while another member is in a subnetwork
that does not use STP or that uses rapid STP (RSTP). The second member does