MAC Retention Applications Configuring MAC Retention
page 9-8 OmniSwitch 6800/6850/9000 Network Configuration Guide March 2008
Link Failure
In the following diagram, even if both stack links "a" and "b" of the primary element of Stack 1 go down
almost at the same time (removed by the user or actual link failures), the MAC Retention feature will
remain enabled and the base MAC address will be retained during takeover.
Link Failure
In the above diagram, if the links between the primary and the secondary element and the primary and the
idle element fail, the entire stack will split into two separate stacks. The primary element will become an
independent stack, and the new primary element (after takeover) and the new secondary element will form
another separate stack. Both the stacks will share the same base MAC address.This will lead to the dupli-
cation of MAC address because the software running on the elements will not be able to distinguish
between a crash or two link failures.
In the above scenario, although the duplication of MAC address cannot be prevented, the element can be
configured to generate an SNMP trap. If an SNMP trap is generated, the administrator can release the base
MAC address from the stack consisting of the new primary and secondary elements. This stack will use
the base MAC address from the EEPROM of the new primary element of the stack.
1
2
3
a
a
a
b
b
b
Idle / New Secondary
Element
Primary Element
Secondary /
New Primary
Element
Switch 1
Stack 1
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