Resilient Ethernet Protocol (REP) is a

network protocol A communication protocol is a system of rules that allows two or more entities of a communications system to transmit information via any variation of a physical quantity. The protocol defines the rules, syntax, semantics, and synchronization of ...

developed by

Cisco Systems Cisco Systems, Inc. (using the trademark Cisco) is an American multinational corporation, multinational digital communications technology conglomerate (company), conglomerate corporation headquartered in San Jose, California. Cisco develops, m ...

as an alternative to the

Rapid Spanning Tree Protocol The Spanning Tree Protocol (STP) is a network protocol that builds a loop-free logical topology for Ethernet networks. The basic function of STP is to prevent bridge loops and the broadcast radiation that results from them. Spanning tree also al ...

(STP). Designed to enhance network reliability, REP mitigates the formation of loops, expedites recovery from link failures, and optimizes convergence times. It achieves this by managing a collection of ports that form a REP segment, ensuring the absence of bridging loops within that segment and facilitating rapid response to any interruptions in connectivity. A REP segment is essentially a sequence of interconnected ports that share a common segment identifier. Each segment is composed of regular segment ports and a pair of edge ports configured by the user. Limitations are placed on the configuration: * A single switch is restricted to having at most two ports in the same segment * REP is supported only on Trunk ports. REP was initially designed to operate with

Fast Ethernet In computer networking, Fast Ethernet Ethernet physical layer, physical layers carry traffic at the nominal rate of . The Classic Ethernet, prior Ethernet speed was . Of the Fast Ethernet physical layers, 100BASE-TX is by far the most common. ...

(FE 10/100) interfaces, where it boasts a rapid link down detection time of approximately 10 milliseconds (ms) and a network convergence time around 50 ms. However, the performance of REP varies when deployed over different media types. For

Fiber Fiber (spelled fibre in British English; from ) is a natural or artificial substance that is significantly longer than it is wide. Fibers are often used in the manufacture of other materials. The strongest engineering materials often inco ...

Gigabit Ethernet (GE) ports, the link down detection time remains at an expedient 10 ms, similar to that of Fast Ethernet ports. Conversely, when REP is implemented on

Gigabit Ethernet In computer networking, Gigabit Ethernet (GbE or 1 GigE) is the term applied to transmitting Ethernet frames at a rate of a gigabit per second. The most popular variant, 1000BASE-T, is defined by the IEEE 802.3ab standard. It came into use in ...

copper interfaces, the detection and recovery times for link losses are notably longer, ranging between 750 ms and 350 ms.

Properties

Under normal conditions, where all ports in a segment are functional, one port per VLAN, known as the Alternate (ALT) port, is placed in a blocked state. When a port becomes non-operational due to a link failure, all remaining ports actively forward traffic across all VLANs to maintain network connectivity. In the event of a link failure, the protocol swiftly unblocks alternate ports to restore connectivity. Upon recovery of the failed link, the protocol selects a logically blocked port for each VLAN, ensuring minimal network disruption. In scenarios where REP segments are used within access ring topologies, it is possible to encounter neighboring switches that do not support REP. For such cases, ports facing non-REP switches can be configured as edge no-neighbor ports. These ports have the capability to issue Spanning Tree Protocol Topology Change Notifications (STP TCNs) towards an upstream aggregation switch, thereby maintaining network resilience and performance.

Properties

References

Further reading