Irf Multi-Active Detection; Multi-Active Handling Procedure - HP FlexFabric 12500 Series Configuration Manual

During an IRF merge, members of the IRF fabric that has failed 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
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 multi-active detection (MAD) mechanisms 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 LACP, BFD, ARP, or IPv6 ND 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 differently than BFD MAD, ARP MAD, and ND MAD. To avoid conflicts, do
not use LACP MAD together with any of those mechanisms. However, you can use BFD MAD, ARP MAD,
and ND MAD together.
For a comparison of these MAD mechanisms, see
Collision handling
When MAD detects a multi-active collision, it allows one IRF fabric to forward traffic and sets all the other
IRF fabrics to the Recovery state. The Recovery-state IRF fabrics are inactive and cannot forward traffic.
LACP MAD handles a multi-active collision in the following procedure:
1. Compares the number of members in each fabric.
2. Allows the fabric that has the most members to forward traffic, and sets all other fabrics to the
Recovery state.
3. Compares the member IDs of the masters if all IRF fabrics have the same number of members.
4. Allows the IRF fabric that has the lowest numbered master to forward traffic, and all other fabrics
to the Recovery (inactive) state. To avoid network flapping caused by IRF split, HP recommends
that you configure the lowest numbered member as the master in a two-chassis IRF fabric.
5. Shuts down all physical network ports in the Recovery-state fabrics except for the following ports:
"Enabling IRF auto merge."
8
"Configuring MAD."