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

10-14
Redundancy Groups
Configuring a Redundancy Group
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 num-
ber 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 respon-
sibilities 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 estab-
lish 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 not hear any heartbeats from the first member,
which is waiting for the spanning tree to be established before transmit-
ting messages. The second member assumes that the first member is down
and may attempt to adopt RPs when it should not.
When you select the Handle STP convergence box, the module waits
50 seconds, which is the standard time period allowed for STP conver-
gence, before attempting to establish the redundancy group.
9. Click the Apply button to apply changes to the running-config.
Adding Members to the Redundancy Group
You must manually specify the IP address of every other module in the
redundancy group. Follow these steps to define each member:
1. Select Network Setup > Redundancy Group and select the Member tab.