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Troubleshooting Virtual Router Redundancy Protocol (VRRP) CMM Failover
OmniSwitch Troubleshooting Guide September 2005 page 13-5
CMM Failover
When the CMM receives a Takeover message from the Chassis Supervisor it will first inform ARP to
purge all entries for the virtual router IP/Mac addresses.
VRRP will then continue with a normal start-up procedure, even though interfaces are already enabled
upon bootup of secondary. If the switch is the virtual IP address owner the switch will become the Master
and add the appropriate entries for the Virtual IP address/MAC address to the ARP table. For all other
configured virtual routers the routers will become back up.
There will be a time during a fail over that the system will not be sending VRRP advertisements. If the
failover interval exceeds the Master Timeout Interval (the timer that tells a back-up it needs to take over as
the master. Formula for this interval is found in the RFC.) The backup Router will take over as the Master.
However the ARP and HRE tables on the Network Interface (NI) cards will still contain the virtual IP/
MAC entries. As a consequence there could be a short period of time that 2 routers will be responding to
packets for the Virtual address. This will stop when VRRP is activated on the secondary CMM and the
ARP and HRE tables are cleared.
Important Information about using the CLI Command set for VRRP:
• A virtual router must be disabled before it may be modified.
• If a password is configured for VRRP authentication, the same password must be configured for all
participating VRRP routers.
• A value of 255 indicates that the VRRP router owns the IP address, that is, that the router contains the
real physical interface to which the IP address is assigned. The system automatically sets this value to
255 if it detects that this router is the IP address owner. The IP address owner will always be the master
router if it is available.
• VRRP routers backing up a virtual router must use priority values from 1 to 254. The default priority
value for VRRP routers backing up a virtual router is 100. If you configure more than one backup, their
priority values should be different. Preempt and no preempt settings specifies whether or not a higher
priority router may preempt a lower priority router.
• The system sets the priority value to zero in the last VRRP advertisement packet before a master router
is shut down (when a router is added or deleted to the configuration).