User Reference Manual.book

Control Modules
24-7 Networks and VRRP
In most networks, one to five minutes is too long to wait for a system to come back on line—VRRP
was created for this reason. The VRRP protocol uses another X-Pedition to take over in the case of
a fail-over. If the backup VRRP router fails to receive messages from the master VRRP router for
three seconds (the default), the backup VRRP router will take over. Enterasys recommends the
VRRP method for 24-7 networks that use the X-Pedition for routing.
If you want the added security of having a backup beyond that of VRRP, Enterasys recommends
using a backup Control Module. If the Primary CM on the Master VRRP router fails, the backup
VRRP router will take over—meanwhile, the backup CM will take over and bring the downed
router back up.
Note: As a general rule, VRRP provides the quickest recovery time with layer-3 routing. If you
use the X-Pedition only as a layer-2 switch, you cannot use VRRP and must use a backup
CM to provide additional reliability.
Identifying the Primary and Backup Control Modules in a Dual CM Environment
Control Modules may reside in slots CM or CM/1 on the XP-8000/8600, and slots 8 or 9 on the
ER16. Except in cases where a system failover has occurred, slot CM on the XP-8000/8600 and
slot 8 on the ER16 contain the Primary Control Module. To determine which Control Module is
currently operating as the Primary CM and which is the Backup CM, examine the LEDs. On the
Primary Control Module, the Online LED is lit—on the Backup Control Module, the Offline LED
is lit.
Note: The Offline LED on the Control Module has a different function than the Offline LED
on a line card. On a line card, it means that the line card has been deactivated. On a
Control Module, a lit Offline LED means that the module is standing by to take over
as the Primary CM if necessary; it does not mean that the Control Module has been
deactivated.
Removing the Primary Control Module
It is important to note that users cannot remove a Primary CM by simply pressing the hot swap
button or entering the hot swap command from the CLI. The Primary CM must first assume the
role of Backup CM through a forced failover.
WARNING The X-Pedition and its components are sensitive to static discharge. To prevent
electrostatic damage, observe the guidelines provided in Preventing Electrostatic
Damage on page 17.
1. Force the failover of the Primary CM by entering the following command from the CLI:
xp# system failover master-cm
2. After some minor LED activity the Offline LED will light, indicating that the Control
Module has assumed the role of Backup CM.
22 Enterasys X-Pedition User Reference Manual