2
processing capacity of an IRF fabric simply by adding member devices without changing the
network topology.
Network topology
An IRF fabric can use a daisy-chain or ring topology. IRF does not support the full mesh topology. For
information about connecting IRF member devices, see "
Connecting IRF physical interfaces
Basic concepts
IRF member roles
IRF uses two member roles: master and standby (called subordinate throughout the
documentation).
When devices form an IRF fabric, they elect a master to manage and control the IRF fabric, and all
the other devices back up the master. When the master device fails, the other devices automatically
elect a new master. For more information about master election, see "
IRF member ID
An IRF fabric uses member IDs to uniquely identify and manage its members. This member ID
information is included as the first part of interface numbers and file paths to uniquely identify
interfaces and files in an IRF fabric. For more information about interface and file path naming, see
"
File system naming conventions
If two devices have the same IRF member ID, they cannot form an IRF fabric. If the IRF member ID
of a device has been used in an IRF fabric, the device cannot join the fabric.
IRF port
An IRF port is a logical interface that connects IRF member devices. Every IRF-capable device
supports two IRF ports. The IRF ports are named IRF-port
n
/1 and IRF-port
n
/2, where
n
is the
member ID of the device. The two IRF ports are referred to as IRF-port 1 and IRF-port 2 in this book.
To use an IRF port, you must bind a minimum of one physical interface to it. The physical interfaces
assigned to an IRF port automatically form an aggregate IRF link. An IRF port goes down only if all
its IRF physical interfaces are down.
IRF physical interface
IRF physical interfaces connect IRF member devices and must be bound to an IRF port. They
forward the IRF protocol packets between IRF member devices and the data packets that must
travel across IRF member devices.
For more information about physical interfaces that can be used for IRF links, see "
MAD
An IRF link failure causes an IRF fabric to split in two IRF fabrics operating with the same Layer 3
settings, 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.
IRF domain ID
One IRF fabric forms one IRF domain. IRF uses IRF domain IDs to uniquely identify IRF fabrics and
prevent IRF fabrics from interfering with one another.
As shown in
, IRF fabric 1 contains Device A and Device B, and IRF fabric 2 contains Device
C and Device D. Both fabrics use the LACP aggregate links between them for MAD. When a
member device receives an extended LACPDU for MAD, it checks the domain ID to see whether the
packet is from the local IRF fabric. Then, the device can handle the packet correctly.
