Reference Guide

two instances of FRRP running on it: one for each ring. The example topology that follows shows R3 assuming the role of
a Transit node for both FRRP 101 and FRRP 202.
Important FRRP Points
FRRP provides a convergence time that can generally range between 150ms and 1500ms for Layer 2 networks.
The Master node originates a high-speed frame that circulates around the ring. This frame, appropriately, sets up or
breaks down the ring.
• The Master node transmits ring status check frames at specified intervals.
• You can run multiple physical rings on the same switch.
• One Master node per ring — all other nodes are Transit.
• Each node has two member interfaces — primary and secondary.
• There is no limit to the number of nodes on a ring.
• Master node ring port states — blocking, pre-forwarding, forwarding, and disabled.
• Transit node ring port states — blocking, pre-forwarding, forwarding, and disabled.
• STP disabled on ring interfaces.
• Master node secondary port is in blocking state during Normal operation.
• Ring health frames (RHF)
– Hello RHF: sent at 500ms (hello interval); Only the Master node transmits and processes these.
– Topology Change RHF: triggered updates; processed at all nodes.
Important FRRP Concepts
The following table lists some important FRRP concepts.
Concept Explanation
Ring ID Each ring has a unique 8-bit ring ID through which the ring is identified (for example, FRRP 101
and FRRP 202, as shown in the illustration in Member VLAN Spanning Two Rings Connected by
One Switch.
Control VLAN Each ring has a unique Control VLAN through which tagged ring health frames (RHF) are sent.
Control VLANs are used only for sending RHF, and cannot be used for any other purpose.
Member VLAN Each ring maintains a list of member VLANs. Member VLANs must be consistent across the
entire ring.
Port Role Each node has two ports for each ring: Primary and Secondary. The Master node Primary port
generates RHFs. The Master node Secondary port receives the RHFs. On Transit nodes, there
is no distinction between a Primary and Secondary interface when operating in the Normal
state.
Ring Interface State Each interface (port) that is part of the ring maintains one of four states”
• Blocking State — Accepts ring protocol packets but blocks data packets. LLDP, FEFD,
or other Layer 2 control packets are accepted. Only the Master node Secondary port
can enter this state.
• Pre-Forwarding State — A transition state before moving to the Forward state. Control
traffic is forwarded but data traffic is blocked. The Master node Secondary port
transitions through this state during ring bring-up. All ports transition through this state
when a port comes up.
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