1-6An IRF typically has a daisy chain connection, that is, IRF-port1 of a device is connected to IRF-port2 ofanother device, and the two devices are connected to form a single straight connection, as shown inFigure 1-5.Figure 1-5 Physical connections of IRFIRF-port1IRF-port2IRFMaster SlaveThe orange line in the figure represents the IRF link, which is different from a common Ethernet networkcable. An IRF link can be composed of either one physical cable or multiple physical links.Topology CollectionEach member in an IRF exchanges hello packets with the directly connected neighbors to collecttopology of the entire IRF. The IRF hello packets carry topology information, including IRF portconnection states, member IDs, priorities, and bridge MAC addresses.Each member is managed by its local active SRPU, which records its known topology informationlocally. At the initiation of the device startup, the local active SRPU records topology information of thelocal device. When an IRF port of a member becomes up, the local active SRPU performs the followingoperations:1) Sends its known topology information from this port periodically.2) Upon receiving the topology information from the directly connected neighbor, it updates the localtopology information.3) If there is a local standby SRPU configured, the local active SRPU synchronizes its recordedtopology information to the local standby SRPU to ensure that the topology information on bothSRPUs is consistent.After topology collection lasts for a period of time, all members have obtained the complete topologyinformation (known as topology convergence), and then the IRF will enter the next stage: role election.Role ElectionThe process of defining the role (master or slave) of IRF members is role election.Role election is held when the topology changes, such as, forming an IRF, adding a new member,leaving or failure of the master, or IRF merge. The role election principles are as follows:z 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 willbe skipped)z A member with a higher priority wins.z A member with the longest system up-time wins. (The system up-time information of each device isdelivered through IRF hello packets)z A member with the lowest bridge MAC address wins.The master is elected according to the above principles one by one, until the only winner is found out.
