H3C Technologies H3C S12500 Series Switches - Manual (Page 16)

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1. Current master, even if a new member has higher priority.
When an IRF fabric is being formed, all member devices consider themselves as the master, and
this rule is skipped.
2. Member with higher priority.
3. Member with the longest system uptime.
4. Member with the lowest bridge MAC address.
The IRF fabric is formed on election of the master.
During an IRF merge, the members of the IRF fabric that fails the master election must reboot to rejoin the
IRF fabric that wins the election. The reboot can be performed automatically or manually, depending on
the configuration. See " Enabling auto reboot for IRF fabric merge ."
After a master election, all subordinate devices reboot with the configuration on the master. The
configuration files of the subordinate members are still retained, but these files do not take effect in the
IRF fabric. A subordinate member reboots with its own startup configuration file only when it is converted
to the standalone mode.
IRF multi-active detection
An IRF link failure causes an IRF fabric to split in two IRF fabrics operating with the same Layer 3
configurations, including the same IP address. To avoid IP address collision and network problems, IRF
uses the multi-active detection (MAD) mechanism to detect the presence of multiple identical IRF fabrics,
handle collisions, and recover from faults.
Multi-active handling procedure
The multi-active handling procedure includes detection, collision handling, and failure recovery.
Detection
The MAD implementation of this device detects active IRF fabrics with the same Layer 3 global
configuration by extending the Link Aggregation Control Protocol (LACP), the Bidirectional Forwarding
Detection (BFD) protocol, or the Gratuitous Address Resolution (ARP) protocol.
These MAD mechanisms identify each IRF fabric with a domain ID and an active ID (the member ID of
the master). If multiple active IDs are detected in a domain, MAD determines that an IRF collision or split
has occurred.
You can use at least one of these mechanisms in an IRF fabric, depending on your network topology.
IMPORTANT:
LACP MAD handles collisions in a different way than BFD MAD and ARP MAD. To avoid conflicts, do not
use LACP MAD together with BFD MAD or ARP MAD. However, you can use BFD MAD and ARP MAD
together.
For a comparison of these MAD mechanisms, see " Configuring MAD ."
Collision handling
MAD mechanisms remove multi-active collisions by setting one IRF fabric to the Detect state and other IRF
fabrics to the Recovery state. The Detect-state IRF fabric is active. The Recovery-state IRF fabric is inactive.
Only members in the Detect-state fabric can continue to forward traffic.