Configuring Virtual Chassis Virtual Chassis Overview
OmniSwitch AOS Release 7 Network Configuration Guide June 2013 page 9-11
Virtual Chassis - Redundancy
• If the Master chassis goes down the Slave chassis will takeover the Master role and all traffic flows
that are based on the multi-homed physical connections will reconverge on the new Master.
• If the Slave chassis goes down the Master chassis will retain its Master role and all traffic flows that
are based on multi-homed physical connections will reconverge on the existing Master.
• If the VFL goes down, the Master chassis will retain its Master role. The Slave chassis will transition
to assume the Master role as well. At this point the virtual chassis topology has been split and there
will be two Masters in the network. If a management EMP network has been configured the Remote
Chassis Detection (RCD) protocol will detect this split topology. In response to this event, the former
Slave chassis will shutdown all its front-panel user ports to prevent duplicate IP and chassis MAC
addresses in the network. The Slave's chassis status will be modified from Running to Split-Topology
to indicate this second pseudo-master chassis is not operational at this point. If theVFL comes back up,
the former Slave chassis will reboot and rejoin the virtual chassis topology assuming its Slave role
again.
• If the primary CMM on the Master chassis fails the secondary CMM, if available, will takeover and the
chassis will remain the Master chassis.
• If all CMMs on the Master chassis fail the chassis will reboot and the first-in-line Slave chassis will
take over becoming the new Master chassis. The first-in-line is derived from the same election criteria
that were used to select the original Master.
Split Chassis Detection
Split chassis detection is implemented using a proprietary protocol called RCD (Remote Chassis Detec-
tion) protocol. The goal of the split-chassis detection mechanism is to provide information in a virtual
chassis environment which can be used to determine whether a VFL has failed. A split chassis can occur
when the VFL connection is broken but each of the switches remains operational. This scenario must be
detected so that one of the switches remains the Master and continues using the same IP and MAC address
in the network.
Note. RCD is only enabled once the virtual chassis is operational. If a switch is unable to join a virtual for
any reason, the RCD protocol will not be enabled.
To help detect this scenario each switch in the Virtual Chassis topology periodically sends information via
its local EMP port. All of the switches participating in a Virtual Chassis should be able to communicate
via the local EMP port using an out-of-band network. When a VFL goes down, each switch can still
communicate with the others via the EMP port, this acts as a backup mechanism to help detect the split
chassis scenario. RCD will use the following IP addresses in order of preference:
1 CMM IP address stored in NVRAM (if configured)
2 Chassis EMP IP address
See the “Configuring EMP IP Addresses” on page 9-21 for information on configuring the EMP IP
addresses. Also, see the “Split Chassis Detection - OS10K CMMs” on page 9-12 for information on EMP
communication between CMMs.
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