Topology Collection; Role Election - 3Com 4210G Series Configuration Manual

addition, you can only bind IRF-port 1 to physical IRF ports 1 and 2, and IRF-port 2 to physical ports 3
and 4.
If one dual-port interface module and one single-port interface module are installed, you can bind two
physical IRF ports on the dual-port interface module to the IRF port in aggregate mode, and bind the
physical IRF port on the single-port interface module to the other IRF port in non-aggregate mode. In
this situation, IRF-port 2 or IRF-port 1 can be bound to any physical port on the device, because only
one IRF port is needed on Switch B or Switch C.

Topology Collection

Each device in an IRF exchanges hello packets with the directly connected neighbors to collect
topology of the entire IRF. The hello packets carry topology information, including IRF port connection
states, member IDs, priorities, and bridge MAC addresses.
Each member records its known topology information locally. At the initiation of the collection, the
members record their own topology information. When an IRF port of a member becomes up, the
member sends its known topology information from this port periodically. Upon receiving the topology
information, the directly connected neighbor updates the local topology information.
The collection process lasts for a period of time. When all members have obtained the complete
topology information (known as topology convergence), the IRF will enter the next stage: role election.

Role Election

An IRF is composed of multiple member devices; each member has a role, which is either master or
slave. The process of defining the role of IRF members is role election.
Role election is held when the topology is instable, such as, forming an IRF, adding a new member,
IRF split, or IRF merge. The master is elected according to the following principles one by one, until
the only winner is found out:
The current master wins, even if a new member has a higher priority. (When an IRF is being
formed, there is no master, and all member devices consider themselves as the master, so this
principle will be skipped)
A member with a higher priority wins.
A member with the longest system up-time wins.
A member with the lowest bridge MAC address wins.
In this stage, member ID collision, software version loading and IRF merging are also handled, which
are discussed in the later sections.
When a device is booted, it first collects topology information and then participates in the role election.
After that, the IRF system can run normally. When the role election is finished, the IRF enters the next
stage: IRF maintenance.
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