User guide

Virtual Chassis Overview Configuring Virtual Chassis
page 13-8 OmniSwitch AOS Release 8 Switch Management Guide May 2014
Startup Error Mode
If a switch is unable to successfully come up in virtual chassis mode, it enters a special fallback mode
called start up error mode. A switch start up error mode will keep all of its front-panel user ports, includ-
ing the virtual-fabric links member ports disabled. This mode can be identified on the switch by using the
show virtual-chassis topology command. The chassis role will display Inconsistent, whereas the chassis
status will show either one of the following values:
Invalid-Chassis-Id: The chassis is not operational in virtual chassis mode because no valid chassis
identifier has been found in the configuration. Typically this means that the vcsetup.cfg file is
corrupted, empty or contains an invalid (for example out of range) chassis identifier.
Invalid-License: The chassis is not operational in virtual chassis mode because a needed license has
not been found.
Master/Slave Election
Once all switches complete their initialization their VFLs become operational, they start the virtual chas-
sis protocol. This protocol performs three basic functions including: topology discovery, master election
and keep-alive/hello monitoring. The election of the Master chassis is based on the following criteria,
which are listed from the higher to the lower priority.
1. Current Master Chassis - The current master chassis will remain the master chassis if it is not rebooted.
2. Highest chassis priority value
3. Longest chassis uptime
4. Smallest Chassis ID value
5. Smallest chassis MAC address
Virtual Chassis - Redundancy
If the Master chassis goes down a Slave chassis will takeover the Master role.
If a Slave chassis goes down the Master chassis will retain its Master role.
If a VFL goes down in a ring topology, the Master chassis will retain its Master role and the VC will
continue to function normally.
The a VFL goes down in a linear topology, a Slave chassis will transition to assume the Master role. At
this point the virtual chassis topology has been split and there will be two Masters in the network.
Virtual Chassis Split Protection (VCSP)
Virtual chassis split protection is implemented using the proprietary VCSP protocol. The goal of the VCSP
mechanism is to provide information in a virtual chassis environment which can be used to determine
whether a VFL has failed and resulted in a split VC. A split VC can occur when one or multiple VFL
connections are broken but each of the switches remains operational. This scenario must be detected so
that only one of the switches remains the Master and continues using the same IP and MAC address in the
network.
See the “Virtual Chassis Split Protection (VCSP)” on page 13-12 for information on configuring VCSP.