User Manual

Enterasys X-Pedition User Reference Manual 19
Control Modules
Note: On an XP-8000/8600, you can install either a line card or a Control Module in slot CM/1,
but you can install only a Control Module in slot CM. On the ER16, control modules will
operate only in slots 8 and 9—slot 8 is reserved for the Primary control module.
WARNING You must install the PCMCIA card before you install the CM or while the CM is
on standby after a hot swap. Do not remove a PCMCIA card while the unit is
powered on.
5. Secure the Control Module. To secure the control module in an ER16, close the ejectors and
use a flathead screwdriver to tighten the screw on each ejector. For all other routers, align the
captive screws with the holes in the face of the router and tighten to secure the module to the
chassis.
Dual CM Environments
CM Fail-Over
The problem with using only one CM is that it can fail or get into a hung state from which it may
not recover. If the CM fails, you must physically remove and replace the bad CM before the
X-Pedition will be of use again. In order for the X-Pedition to recover from a hung state, you must
turn the power off and on and allow the X-Pedition to reboot. However, with a backup CM, the
X-Pedition can recover more quickly—without human intervention.
An X-Pedition with dual CMs operates as it normally would with one CM—until the Primary CM
fails. For example, if the Primary CM (in slot 0) fails or hangs, the backup CM (in slot 1) takes
control of router operations and restarts the CM in slot 0. Unless the failure was catastrophic, the
CM in slot 0 will restart. Once the CM in slot 0 restarts, it will recognize that the backup CM in slot
1 has taken over and assumed the role of the primary CM (the CM in slot 0 then assumes the role of
the backup CM). The CM status (primary versus backup) will remain the same until the CM in slot
1 (the current Primary CM) fails or hangs. When this occurs, the process will repeat itself and the
CM in slot 0 will again be the Primary CM and the CM in slot 1 will be the Secondary CM.
Note: In a dual Control Module configuration, the MAC address of the Primary Control Module
in slot “CM/0” is used for both Control Modules after the system is booted. If the Control
Module in slot “CM/0” is removed and not replaced after a fail-over, or if it is replaced
with a new Control Module and the system is rebooted, the system will use the MAC
address of the Control Module in slot 1 (i.e., the new Control Module).
When you install a backup CM, it will only come up part way. The CM will remain on standby until
the heartbeat messages from the Primary CM stop coming for at least 4 seconds. Then the
Secondary CM will take control of the X-Pedition.