Dell S4048T, Configuration Manual

Page: 399 / 1277

Force10 Resilient Ring Protocol
(FRRP)
FRRP provides fast network convergence to Layer 2 switches interconnected in a ring topology, such as a
metropolitan area network (MAN) or large campuses. FRRP is similar to what can be achieved with the
spanning tree protocol (STP), though even with optimizations, STP can take up to 50 seconds to converge
(depending on the size of network and node of failure) and may require 4 to 5 seconds to reconverge. FRRP
can converge within 150ms to 1500ms when a link in the ring breaks (depending on network configuration).
To operate a deterministic network, a network administrator must run a protocol that converges
independently of the network size or node of failure. FRRP is a proprietary protocol that provides this
flexibility, while preventing Layer 2 loops. FRRP provides sub-second ring-failure detection and
convergence/re-convergence in a Layer 2 network while eliminating the need for running spanning-tree
protocol. With its two-way path to destination configuration, FRRP provides protection against any single link/
switch failure and thus provides for greater network uptime.
Topics:
• Protocol Overview
• Implementing FRRP
• FRRP Configuration
• Troubleshooting FRRP
• Sample Configuration and Topology
Protocol Overview
FRRP is built on a ring topology.
You can configure up to 255 rings on a system. FRRP uses one Master node and multiple Transit nodes in
each ring. There is no limit to the number of nodes on a ring. The Master node is responsible for the
intelligence of the Ring and monitors the status of the Ring. The Master node checks the status of the Ring by
sending ring health frames (RHF) around the Ring from its Primary port and returning on its Secondary port. If
the Master node misses three consecutive RHFs, the Master node determines the ring to be in a failed state.
The Master then sends a Topology Change RHF to the Transit Nodes informing them that the ring has
changed. This causes the Transit Nodes to flush their forwarding tables, and re-converge to the new network
structure.
One port of the Master node is designated the Primary port (P) to the ring; another port is designated as the
Secondary port (S) to the ring. In normal operation, the Master node blocks the Secondary port for all non-
control traffic belonging to this FRRP group, thereby avoiding a loop in the ring, like STP. Layer 2 switching
and learning mechanisms operate per existing standards on this ring.
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