Allied Telesis AT-9924T-40, X900-48FE-N, AT-9924T/4SP-A-20, AT-8948 How Epsr Works, Epsr Components

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How EPSR Works

How EPSR Works

EPSR operates on physical rings of switches (note, not on meshed networks). When all nodes and links in the ring are up, EPSR prevents a loop by blocking data transmission across one port. When a node or link fails, EPSR detects the failure rapidly and responds by unblocking the blocked port so that data can flow around the ring.

In EPSR, each ring of switches forms an EPSR domain. One of the domain’s switches is the master node and the others are transit nodes. Each node connects to the ring via two ports.

One or more data VLANs sends data around the ring, and a control VLAN sends EPSR messages. A physical ring can have more than one EPSR domain, but each domain operates as a separate logical group of VLANs and has its own control VLAN and master node.

On the master node, one port is the primary port and the other is the secondary port. When all the nodes in the ring are up, EPSR prevents loops by blocking the data VLAN on the secondary port.

The master node does not need to block any port on the control VLAN because loops never form on the control VLAN. This is because the master node never forwards any EPSR messages that it receives.

The following diagram shows a basic ring with all the switches in the ring up.

 

End User Ports

 

 

 

 

 

 

 

 

 

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epsr-basic-ring

EPSR Components

EPSR domain:

A protection scheme for an Ethernet ring that consists of one or more data VLANs and a control VLAN.

Master node:

The controlling node for a domain, responsible for polling the ring state, collecting error messages, and controlling the flow of traffic in the domain.

Transit node:

Other nodes in the domain.

Ring port:

A port that connects the node to the ring. On the master node, each ring port is either the primary port or the secondary port. On transit nodes, ring ports do not have roles.

Primary port:

A ring port on the master node. This port determines the direction of the traffic flow, and is always operational.

Secondary port:

A second ring port on the master node. This port remains active, but blocks all protected VLANs from operating unless the ring fails. Similar to the blocking port in an STP/RSTP instance.

Control VLAN:

The VLAN over which all control messages are sent and received. EPSR never blocks this VLAN.

Data VLAN

A VLAN that needs to be protected from loops. Each EPSR domain has one or more data VLANs.

Page 3 AlliedWare™ OS How To Note: EPSR

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Contents What information will you find in this document? IntroductionWhich products and software versions does it apply to? Epsr Components How Epsr WorksEstablishing a Ring Fault in a link or a transit node Recovering from a FaultFault in the master node Transit Nodes with Both Ports Down Restoring Normal OperationMaster Node Transit Nodes with One Port DownConfiguring Epsr How To Configure EpsrConfigure other ports and protocols as required Iii. Remove the ring ports from the default VlanIv. Configure the Epsr domain Enable EpsrModifying the Control Vlan Example 1 a Basic Ring Configure the Master Node aAdd the data Vlan to the domain Configure the Transit Nodes B and CRemove the ring ports from the default Vlan Create the Epsr domainCreate epsr=test mode=transit controlvlan=vlan1000 Example 2 a Double Ring Configure the master node switch a for domainConfigure Epsr Configure the master node switch C for domainConfigure the data Vlan for domain Example 3 Epsr and Rstp Configure the master node switch a for the Epsr domainRemove the STP VLAN’s ports from the default Vlan Configure switch E for Epsr and Rstp Epsr Domain Example 4 Epsr with Nested VLANsConfigure the Epsr control Vlan Configure client switch H connected to transit node D Configure client switch E connected to the master nodeConfigure client switch F connected to transit node B Configure client switch G connected to transit node CExample 5 Epsr with management stacking Configure stacking on the second transit node host3 Configure stacking on the first transit node host2Configure Epsr on the stacked switches Configure the other VLANs on the stacked switchesExample 6 Epsr with an iMAP Configure the AT-TN7100 iMAP as Master NodeFollowing diagram shows the expected output Checking the Master Node ConfigurationChecking the Transit Node Configuration Configure the AT-TN7100 iMAP as a Transit NodeLINKS-UP Classifiers and Hardware FiltersPorts and Recovery Times Health Message Priority Igmp Snooping and Recovery TimesEpsr State and Settings Epsr Information Name Domain1 Snmp Traps Counters Master node sends Health messages DebuggingLink Down Between Master Node and Transit Node Master Node Node a Debug OutputPrimary port goes down Master node continues sending Health messagesMaster node transmits a Ring-Down-Flush-FDB message Hello timer expires Hello timer expires againPrimary port comes back up Master node receives the Ring-Up-Flush-FDB message on port Master node returns the ring to a state of CompleteMaster node transmits and receives Health messages Transit node receives Health messages Transit Node Node B Debug OutputTransit node receives a Ring-Down-Flush-FDB message Port 1 on the transit node goes downTransit node receives a Health message Port 1 comes back upTransit node receives a Ring-Up-Flush-FDB message 252 Link Down Between Two Transit Nodes Link between the two transit nodes goes down Master node receives a second Link-Down message Master node receives a Health message 51 AlliedWare OS How To Note Epsr 375 53 AlliedWare OS How To Note Epsr Transit node sends a Link-Down message Transit node receives another Health message Link comes back upTransit node receives a Ring-Up-Flush-FDB message

AT-9924SP-30, AT-9924T-40, AT-8948, AT-9924T/4SP-A-20, X900-48FE-N specifications

Allied Telesis is a leading provider of networking solutions, renowned for its innovative technologies and high-performance networking equipment. Among its extensive product lineup, the X900-48FE-N, AT-9924T-40, AT-8948, AT-9924T/4SP-A-20, and AT-9924SP-30 stand out for their remarkable features and capabilities.

The X900-48FE-N is a robust layer 2/3 managed switch that features 48 Fast Ethernet ports. This model is particularly known for its energy efficiency and reliability, making it a suitable choice for enterprises with demanding networking needs. It supports a wide range of Layer 2 Ethernet switching technologies, including VLANs, Spanning Tree Protocol (STP), and Link Aggregation Control Protocol (LACP), which enhances network reliability and efficiency.

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In summary, these Allied Telesis models showcase advanced features, network reliability, and versatile management options, making them critical components for efficient and scalable networking solutions.
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