- Audience
- Getting Started with Cisco ME 2600X
- Ethernet Virtual Circuit
- Quality of Service
- Resilient Ethernet Protocol
- Link Aggregation Group and Link Aggregation Control Protocol
- MAC Learning
- Multicast VLAN Registration
- IGMP Snooping
- Remote Network Monitoring and Alarm Troubleshooting
- Authentication, Authorization, and Accounting (AAA)
- Cisco Discovery Protocol
- SNMP
- IP Source Guard for Service Instance
- DHCP Snooping
- Dynamic ARP Inspection
- MAC Address Security
- Layer 2 Access Control Lists on EVCs
- Layer 3 Access Control Lists on EVCs
- Storm Control over EVC
- Control Plane Policing
- ICMP Unreachable Rate Limiting User Feedback
- IP Version 6 Support for the Management Port
- SSH
- PPPoE Intermediate Agent
- CFM over EVC
- Index
Cisco ME 2600X Series Ethernet Access Switch Software Configuration Guide
- Updated:
- November 17, 2017
Chapter: Resilient Ethernet Protocol
Contents
- Resilient Ethernet Protocol
- Understanding Resilient Ethernet Protocol
- Understanding REP Segments
- Understanding Link Adjacency
- Understanding Fast Convergence
- REP Edge No-Neighbor
- Understanding REP Ports
- REP Actions on Packets
- Default REP Configuration
- REP Configuration Guidelines
- REP Configuration Sequence
- Understanding REP Administrative VLAN
- REP Configuration Procedures
- Configuring REP Administrative VLAN
- Configuring REP
- Enabling REP on a Port
- Configuring STCN on the Primary Edge Port
- Configuring Preemption Delay on the Primary Edge Port
- Example: Configuring a REP Interface
- Understanding VLAN Load Balancing
- Configuring VLAN Load Balancing
- Configuring VLAN Load Balancing on the Primary Edge Port
- Configuring the Preemption for VLAN Load Balancing
- Understanding REP Configurable Timers
- Configuring REP Timers
- Configuring REP Link Status Layer Retries
- Configuring the REP Link Status Layer Ageout Timer
- Understanding REP with EVC
- Configuring REP over EVC
- Configuring REP over EVC Using a Cross–Connect
- Configuring REP over EVC Using the Bridge Domain
- Verifying REP with EVC Configuration
- REP with Multicast
Resilient Ethernet Protocol
This chapter describes Resilient Ethernet Protocol (REP), REP configuration guidelines, VLAN load balancing, REP timers, and REP over EVC. This chapter also describes procedures to configure REP.
- Understanding Resilient Ethernet Protocol
- Understanding VLAN Load Balancing
- Understanding REP Configurable Timers
- Understanding REP with EVC
- REP with Multicast
Understanding Resilient Ethernet Protocol
The Resilient Ethernet Protocol (REP) is a protocol that provides an alternative to Spanning Tree Protocol (STP) to support layer 2 resiliency, and fast switchover with Ethernet networks. REP provides a way to control network loops, handle link failures, and improve convergence time.
REP performs the following tasks:
- Understanding REP Segments
- Understanding Link Adjacency
- Understanding Fast Convergence
- REP Edge No-Neighbor
- Understanding REP Ports
- REP Actions on Packets
- Default REP Configuration
- REP Configuration Guidelines
- REP Configuration Sequence
- Understanding REP Administrative VLAN
- REP Configuration Procedures
- Configuring REP Administrative VLAN
- Configuring REP
- Enabling REP on a Port
- Configuring STCN on the Primary Edge Port
- Configuring Preemption Delay on the Primary Edge Port
- Example: Configuring a REP Interface
Understanding REP Segments
A REP segment is a chain of ports connected to each other and configured with a segment ID. Each segment consists of standard (non-edge) segment ports and two user-configured edge ports. The two edge ports terminate the segments.
A device cannot have more than two ports that belong to the same segment, and each segment port can have only one external neighbor. A segment can go through a shared medium, but on any link only two ports can belong to the same segment. REP is supported only on Layer 2 interfaces.
The figure below shows an example of a segment consisting of six ports spread across four switches. Ports E1 and E2 are configured as edge ports. When all ports are operational (that is, the segment on the left), a single port is blocked, shown by the diagonal line. When there is a failure in the network, the blocked port returns to the forwarding state to minimize network disruption.
The segment shown in Figure 1 is an open segment; there is no connectivity between the two edge ports. The REP segment cannot cause a bridging loop and it is safe to connect the segment edges to any network. The traffic from a REP ring node toward the network cloud is sent to either of the edge nodes, depending on the location of the alternate port. If a failure is detected anywhere in the ring, the alternate port changes to a open port forwarding all traffic. This may cause the traffic being redirected to the other edge node depending on the fault location. It ensures that data flow is maintained between a particular REP node and the network cloud. If a failure occurs on any segment or any port on a REP segment, REP unblocks all the ports to ensure that connectivity is available through the other edge.
The segment shown in the figure below, with both edge ports located on the same device, is a ring segment. In this configuration, there is connectivity between the edge ports through the segment. With this configuration, you can create a redundant connection between any two devices in the segment.
Characteristics of REP Segments
REP segments have the following characteristics:
- If all the ports in the segment are operational, one port (referred to as the alternate port) blocks traffic for each VLAN. If VLAN load balancing is configured, two ports in the segment control the blocked state of VLANs.
- If one or more ports in a segment is not operational, causing a link failure, all ports forward traffic on all VLANs to ensure connectivity. The Failed ports are blocked for all traffic, while all the other ports in the ring stay in open state.
- In case of a link failure, the alternate ports are immediately unblocked. When the failed link comes up, a logically blocked port per VLAN is selected with minimal disruption to the network. When VLAN load balancing preemption timer is set, VLAN load balancing is automatically applied after the last failure has recovered. There are 2 alternate ports when VLAN load balancing takes effect.
- Changing the normal REP port configuration to preferred REP port with auto preemption delay configuration requires manual preemption for the first time. Subsequently when a failure occurs, auto preemption takes effect after link recovery and the port becomes the secondary port.
Understanding Link Adjacency
REP does not use an end-to-end polling mechanism between edge ports to verify link integrity. It implements local link failure detection. When enabled on an interface, the REP Link Status Layer (LSL) detects its REP-aware neighbor and establishes connectivity within the segment. All VLANs are blocked on an interface until it detects the neighbor. After the neighbor is identified, REP determines which neighbor port should become the alternate port and which ports should forward traffic.
Each port in a segment has a unique port ID. When a segment port starts, the LSL layer sends packets that include the segment ID and the port ID. The port is declared as operational after it performs a three-way handshake with a neighbor in the same segment.
A segment port does not become operational under the following conditions:
- No neighbor port has the same segment ID.
- More than one neighbor port has the same segment ID.
- The neighbor port does not acknowledge the local port as a peer.
Each port creates an adjacency with its immediate neighbor. When the neighbor adjacencies are created, the ports negotiate to determine one blocked port for the segment, the alternate port. All other ports become unblocked.
Understanding Fast Convergence
A failure in a REP segment is noticed and propagated across the ring by LSL and HFL messages. LSL messages are sent hop by hop on the control plane, with each node receiving, processing, and forwarding LSL messages. This process is time-consuming.
HFL messages are flooded in the data plane across the ring on a preconfigured administrative VLAN, using a fixed multicast address. This results in each node receiving failure notifications instantaneously. Using HFL, traffic reconvergence is achieved fast, leading to insignificant loss of traffic on segment failure.
HFL messages are handled as data packets on the nodes in a ring which do not have the REP configured. The administrative VLAN is common to all the REP segments that are configured on a node.
Convergence time varies depending on the type and number of nodes that are present on the ring.
REP Edge No-Neighbor
You can configure the non-REP switch facing ports as edge no-neighbor ports. These ports inherit the properties of edge ports, and overcome the limitation of not being able to converge quickly during a failure.
You can configure the non-REP facing ports (E1 and E2) as edge no–neighbor ports as shown in the figure below. These ports inherit all the properties of edge ports. You can configure these no-neighbor ports as any other edge port and also enable the ports to send REP topology change notifications to the aggregation switch.
Understanding REP Ports
Ports in REP segments take one of three roles or states—Failed, Open, or Alternate.
- A port configured as a regular segment port starts as a failed port.
- When the neighbor adjacencies are determined, the port transitions to the alternate port state, blocking all the VLANs on the interface. Blocked port negotiations occur and when the segment settles, one blocked port remains in the alternate role and all the other ports become open ports.
- When a failure occurs in a link, all the ports move to the failed state. When the alternate port receives the failure notification, it changes to the open state, forwarding all VLANs.
If you convert an edge port into a regular segment port, VLAN load balancing is not implemented unless it has been configured. For VLAN load balancing, you must configure two edge ports in the segment.
REP Actions on Packets
REP performs specific actions depending on the type of packets.
The following actions are taken by REP on packets that originate from an alternate port.
| Packet type | Block/Allow (TX) | Action (TX) | Block/Allow (RX) | Action (RX) |
|---|---|---|---|---|
| REP LSL packet | Allow | — | Allow | Punt to CPU |
| REP HFL packet | Allow | — | Allow | Punt to CPU; no forward |
| Tagged control packet | Block if VLAN is blocked on the port | — | Block if VLAN is blocked on the port | As per the configured protocol and EVC, if VLAN is not blocked. |
| Untagged control packet | Block | — | Block | — |
| Tagged data packet | Block if VLAN is blocked on the port | — | Block if VLAN is blocked on the port | As per EVC, if VLAN is not blocked. |
| Untagged data packet | Block | — | Block | — |
REP blocks untagged packets on a port only when VLAN load balancing is not in effect. When VLAN load balancing takes effect, all the untagged packets flow across an alternate port.
The following actions are taken by REP on packets that originate from an open port (a port that is not blocked by REP).
| Packet type | Block/Allow (TX) | Action (TX) | Block/Allow (RX) | Action (RX) |
|---|---|---|---|---|
| REP LSL packet | Allow | — | Allow | Punt to CPU |
| REP HFL packet | Allow only packets that originate from the node | — | Allow | Punt to CPU and forward as per EVC |
| Tagged control packet | Allow | — | Allow | As per the configured protocol and EVC |
| Untagged control packet | Allow | — | Allow | As per the configured protocol and EVC |
| Tagged data packet | Allow | — | Allow | As per EVC |
| Untagged data packet | Allow | — | Allow | As per EVC |
Default REP Configuration
REP is disabled on all the interfaces by default. When enabled, the interface is a regular segment port unless it is configured as an edge port.
When REP is enabled, the sending of segment topology change notifications (STCNs) is disabled, all VLANs are blocked, and the administrative VLAN is VLAN 1. When REP administrative VLAN or STCN configuration is changed, the changed configuration applies to ports.
When VLAN load balancing is enabled, the default is manual preemption with the delay timer disabled. If VLAN load balancing is not configured, the default action after manual preemption is to block all the VLANs at the elected alternate port.
REP Configuration Guidelines
Follow these guidelines when configuring REP:
- REP ports must be a Layer 2 IEEE 802.1Q port or 802.1AD port.
- You must configure all trunk ports in the segment with the same set of allowed VLANs, or misconfiguration occurs.
- Be careful when configuring REP through a Telnet connection. Because REP blocks all VLANs until another REP interface sends a message to unblock it or you might lose connectivity to the device if you enable REP in a Telnet session that accesses the device through the same interface.
- If REP is enabled on two ports on a device, both ports must be either regular segment ports or edge ports. REP ports follow these rules:
- If only one port on a device is configured in a segment, the port should be an edge port.
- If two ports on a device belong to the same segment, both ports must be regular segment ports.
- If two ports on a device belong to the same segment and one is configured as an edge port and one as a regular segment port (a misconfiguration), the edge port is treated as a regular segment port.
- REP interfaces come up in a blocked state and do not forward traffic till they change to open ports through exchange of LSL HELLO messages with neighbors. You need to be aware of this to avoid sudden connection losses.
- REP configuration parameters for a port must not be changed without shutting down the port. However, the VLAN range for VLAN load balancing on primary edge port can be changed without this restriction.
- When configuring VLAN load balancing, the port selected for load balancing and the primary edge port must be on different nodes. Otherwise, it may cause HFL packets to flood, when VLAN Load Balancing is activated.
- When configuring STCN, ensure that STCN propagates across the REP segments in one direction. When STCN is sent from a segment, the STCN packet must not reach the original segment. Otherwise, it may cause an infinite loop of STCN packets flowing across the segments.
- REP is not supported on service instances configured with encapsulation, untagged, or default type.
- To avoid traffic drop after configuration change for REP Edge-NN segment, do one of the following:
REP Configuration Sequence
You must perform the following tasks in this sequence to configure REP:
- Configure the REP administrative VLAN. The range of the REP admin VLAN is from 2 to 4094. The default VLAN 1 is always configured for HFL packets. However, EVC configuration must be explicitly done for VLAN 1, or any other VLAN that is selected as an administrative VLAN. See Configuring REP Administrative VLAN.
- Enable REP on ports and assign a segment ID to it. REP is disabled on all ports by default. The range of the segment ID is from 1 to 1024. See Enabling REP on a Port.
- Configure two edge ports in the segment; one port as the primary edge port and the other as the secondary edge port. See Enabling REP on a Port. If you configure two ports in a segment as the primary edge port, for example, ports on different switches, REP selects one of the ports to serve as the primary edge port based on port priority. The Primary option is enabled only on edge ports.
- Configure the primary edge port to send STCNs and VLAN load balancing to another port or to other segments. STCNs and VLAN load balancing configurations are enabled only for edge ports. See Configuring STCN on the Primary Edge Port and Configuring VLAN Load Balancing on the Primary Edge Port.
Understanding REP Administrative VLAN
To avoid the delay introduced by relaying messages related to link-failure or VLAN-blocking notification during VLAN load balancing, REP floods packets at the HFL to a regular multicast address. HFL packets are used for fast transmission of failure notification across a REP ring by flooding a BPA on a VLAN. These messages are flooded to the whole network, not just the REP segment. You can control flooding of these messages by configuring an administrative VLAN for the whole domain.
Follow these guidelines when configuring the REP administrative VLAN:
- If you do not configure an administrative VLAN, the default VLAN is VLAN 1. The default VLAN 1 is always configured.
- There can be only one administrative VLAN on a device and on a segment.
The administrative VLAN is configured at the system level. Whenever the administrative VLAN is changed, the corresponding EFP must also be manually configured to match the outer encapsulation for tagged control packets. The EFP must be associated with a bridge domain used exclusively for administrative VLAN EFPs. The VLAN marked as administrative VLAN must not be used for any other service or data traffic.
REP Configuration Procedures
To configure REP, complete the following procedures:
- Configuring REP Administrative VLAN
- Enabling REP on a Port
- Configuring STCN on the Primary Edge Port
- Configuring VLAN Load Balancing on the Primary Edge Port
- Configuring Preemption Delay on the Primary Edge Port
- Configuring the Preemption for VLAN Load Balancing
- Configuring REP Link Status Layer Retries
- Configuring the REP Link Status Layer Ageout Timer
- Configuring REP over EVC Using a Cross–Connect
- Configuring REP over EVC Using the Bridge Domain
- Verifying REP with EVC Configuration
Configuring REP Administrative VLAN
1.
enable
2.
configure terminal
3.
rep admin vlan vlan-id
4.
end
5. show interface [interface-id] rep detail
DETAILED STEPS
Example: Configure REP Administrative VLAN
The following example shows how to configure the administrative VLAN as VLAN 100.
Switch> enable Switch# configure terminal Switch(config)# rep admin vlan 100 Switch(config)# end
Configuring REP
Perform any of the following procedures as needed:
Enabling REP on a Port
Configuring REP Administrative VLAN
 Note | REP can be enabled on Ten Gigabit Ethernet (10 GE) and one Gigabit Ethernet (1 GE) interface. |
1.
enable
2.
configure terminal
3.
interface interface-id
4.
rep segment segment-id [edge [no-neighbor] [primary]] [preferred]
5.
end
6. show interface [interface-id] rep detail
DETAILED STEPS
Configuring STCN on the Primary Edge Port
Note | Perform this procedure only on edge ports and not on regular segment ports. |
1.
enable
2.
configure terminal
3.
interface interface-id
4. rep stcn {interface interface-id | segment segment-id-list}
5.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. |
| Step 3 | interface interface-id Example: Switch(config)# interface TenGigabitEthernet 0/45
| Specifies the interface and enters interface configuration mode. |
| Step 4 | rep stcn {interface interface-id | segment segment-id-list} Example: Switch(config-if)# rep stcn segment 2-5
| Configures the edge port to send STCNs to one or more segments or to an interface. |
| Step 5 | end Example: Switch(config-if)# end
| Returns to privileged EXEC mode. |
Configuring Preemption Delay on the Primary Edge Port
1.
enable
2.
configure terminal
3.
interface interface-id
4.
rep preempt delay value
5.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. |
| Step 3 | interface interface-id Example: Switch(config)# interface TenGigabitEthernet 0/45
| Specifies the interface and enters interface configuration mode. |
| Step 4 | rep preempt delay value Example: Switch(config-if)# rep preempt delay 60
| Configures a preempt time delay. Use this command if you want VLAN load balancing to automatically trigger after a link failure and recovery. The time delay range is from 15 to 300 seconds. The default action is manual preemption with no time delay. |
| Step 5 | end Example: Switch(config-if)# end
| Returns to privileged EXEC mode. |
Example: Configuring a REP Interface
The following example shows how to configure an interface as the primary edge port for segment 1, to send STCNs to segments 2 through 5, and to configure the alternate port as the port with port ID 0009001818D68700 to block all VLANs after a preemption delay of 60 seconds after a segment port failure and recovery.
Switch# configure terminal Switch(config)# interface TenGigabitEthernet 0/45 Switch(config-if)# rep segment 1 edge primary Switch(config-if)# rep stcn segment 2-5 Switch(config-if)# rep block port id 0009001818D68700 vlan all Switch(config-if)# rep preempt delay 60 Switch(config-if)# end
The following example shows how to configure the VLAN blocking configuration shown in the figure below. The alternate port is the neighbor with neighbor offset number 4. After manual preemption, VLANs 100 to 200 are blocked at this port and all other VLANs are blocked at the primary edge port E1 (TenGigabitEthernet 0/45).
Switch# configure terminal Switch(config)# interface TenGigabitEthernet 0/45 Switch(config-if)# rep segment 1 edge primary Switch(config-if)# rep block port 4 vlan 100-200 Switch(config-if)# end
Understanding VLAN Load Balancing
REP supports VLAN load balancing, controlled by the primary edge port but occurring at any port in the segment.
You must configure two edge ports in the segment for VLAN load balancing. One edge port in the REP segment acts as the primary edge port; the other edge port as the secondary edge port.
The primary edge port always participates in VLAN load balancing in the segment. REP VLAN load balancing is achieved by blocking some VLANs at a configured alternate port and all other VLANs at the primary edge port.
Note | When VLAN load balancing is configured, it does not start working until triggered by either manual intervention or a link failure and recovery. |
When VLAN load balancing is triggered, the primary edge port then sends out a message to alert all interfaces in the segment about the preemption. When the message is received by the secondary edge port, it is reflected into the network to notify the alternate port to block the set of VLANs specified in the message and to notify the primary edge port to block the remaining VLANs.
You can also configure a particular port in the segment to block all VLANs. VLAN load balancing is initiated only by the primary edge port and is not possible if the segment is not terminated by an edge port on each end. The primary edge port determines the local VLAN load balancing configuration.
- Configuring VLAN Load Balancing
- Configuring VLAN Load Balancing on the Primary Edge Port
- Configuring the Preemption for VLAN Load Balancing
Configuring VLAN Load Balancing
Perform any of the following procedures as needed:
Configuring VLAN Load Balancing on the Primary Edge Port
1.
enable
2.
configure terminal
3.
interface interface-id
4. rep block port {id port-id | neighbor-offset | preferred} vlan {vlan-list | all}
5.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. |
| Step 3 | interface interface-id Example: Switch(config)# interface TenGigabitEthernet 0/45
| Specifies the interface and enters the interface configuration mode. |
| Step 4 | rep block port {id port-id | neighbor-offset | preferred} vlan {vlan-list | all} Example: Switch(config-if)# rep block port id 0009001818D68700 vlan all
| Configures VLAN load balancing on the primary edge port, identifies the REP alternate port, and configures the VLANs to be blocked on the alternate port.
|
| Step 5 | end Example: Switch(config-if)# end
| Returns to privileged EXEC mode. |
Configuring the Preemption for VLAN Load Balancing
Configuring VLAN Load Balancing on the Primary Edge Port
Ensure that all the other segment configuration has been completed before setting preemption for VLAN load balancing. When you use the rep preempt segment segment-id command, a confirmation message appears before the command is executed because preemption for VLAN load balancing can disrupt the network.
If you do not use the rep preempt delay value interface configuration command on the primary edge port to configure a preemption time delay, the default configuration is to manually trigger VLAN load balancing on the segment. Use the show rep topology privileged EXEC command to see which port in the segment is the primary edge port.
Complete the following steps on the device that has the segment with the primary edge port.
1.
enable
2.
rep preempt segment segment-id
3.
show rep topology
DETAILED STEPS
| Command or Action | Purpose | |||
|---|---|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. | ||
| Step 2 | rep preempt segment segment-id Example: Switch# rep preempt segment 1
| Manually triggers VLAN load balancing on the segment.
| ||
| Step 3 | show rep topology Example: Switch# show rep topology
| Displays the REP topology information. |
Example: Configure the Preemption for VLAN Load Balancing
The following example shows how to set the preemption for VLAN load balancing on a REP segment using Cisco IOS commands.
Switch> enable Switch# rep preempt segment 1
Understanding REP Configurable Timers
The REP Configurable Timer (REP Fast Hellos) feature provides a fast reconvergence in a ring topology with higher timer granularity and quicker failure detection on the remote side. This feature also supports improved convergence of REP segments having nodes with copper based SFPs, where the link detection time varies between 300 ms to 700 ms.
With the REP Link Status Layer (LSL) ageout timer configuration, the failure detection time can be configured between a range of 120 to 10000 ms, in multiples of 40 ms. The result of this configuration is that, even if the copper pull takes about 700 ms to notify the remote end about the failure, the REP configurable timers process will detect it much earlier and take subsequent action for the failure recovery within 200 ms.
The LSL retries and LSL ageout timer is related in terms of LSL hello packet transmission. The LSL hello packet interval is measured by lsl_age_timer/lsl_retries value. The LSL hello packet interval value must be at least 40 ms.
Restrictions for REP timers
- While configuring REP configurable timers, we recommend that you shut the port, configure REP and only then use the no shut command. This prevents the REP from flapping and generating large number of internal messages.
- If incompatible switches are neighbors, configure the correct LSL Age Out value first. In some scenarios, you might not get the expected convergence range.
- While configuring REP configurable timers, we recommend that you configure the REP LSL number of retries first and then configure the REP LSL ageout timer value.
- Configuring REP Timers
- Configuring REP Link Status Layer Retries
- Configuring the REP Link Status Layer Ageout Timer
Configuring REP Timers
Perform any of the following procedures as needed:
Configuring REP Link Status Layer Retries
1.
enable
2.
configure terminal
3.
interface interface-id
4.
rep lsl-retries count
5.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. |
| Step 3 | interface interface-id Example: Switch(config)# interface TenGigabitEthernet 0/45
| Specifies the interface to configure and enters interface configuration mode. |
| Step 4 | rep lsl-retries count Example: Switch(config-if)# rep lsl-retries 4
| Configures the number of retries before the REP link is disabled. The range of retries is from 3 to 10. The default number of LSL retries is 5. |
| Step 5 | end Example: Switch(config-if)# end
| Returns to privileged EXEC mode. |
Example: Configure REP Link Status Layer Retries
The following example shows how to configure REP LSL retries using Cisco IOS commands.
Switch# enable Switch# configure terminal Switch(config)# interface TenGigabitEthernet 0/45 Switch(config-if)# rep segment 2 edge primary Switch(config-if)# rep lsl-retries 4 Switch(config-if)# end
Configuring the REP Link Status Layer Ageout Timer
1.
enable
2.
configure terminal
3.
interface interface-id
4.
rep lsl-age-timer value
5.
end
DETAILED STEPS
| Command or Action | Purpose | |
|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. |
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. |
| Step 3 | interface interface-id Example: Switch(config)# interface TenGigabitEthernet 0/45
| Specifies the interface to configure and enters interface configuration mode. |
| Step 4 | rep lsl-age-timer value Example: Switch(config-if)# rep lsl-age-timer 2000
| Configures REP link status layer ageout timer value. The range of lsl-age-timer is between 120 ms and 10000 ms, in multiples of 40 ms. The default LSL ageout timer value is 5 seconds. The recommended LSL ageout timer value is 2 seconds. |
| Step 5 | end Example: Switch(config-if)# end
| Returns to privileged EXEC mode. |
Example: Configure the REP LSL Ageout Timer
The following example shows how to configure REP LSL ageout timer value using Cisco IOS commands.
Switch# enable Switch# configure terminal Switch(config)# interface TenGigabitEthernet 0/45 Switch(config-if)# rep segment 1 edge primary Switch(config-if)# rep lsl-age-timer 2000 Switch(config-if)# end
Understanding REP with EVC
REP can be integrated with an Ethernet Virtual Circuit (EVC) port using the REP over EVC feature. This feature allows you to configure and manage ports at the service instance level. An EVC port can have multiple service instances. Each service instance corresponds to a unique Ethernet Flow Point (EFP).
This feature allows you to configure an EVC port to participate in a REP segment. REP can selectively block or forward data traffic on particular VLANs. For an EVC, the VLAN ID refers to the outer tag of the encapsulation that is configured on a service instance.
Note | REP is supported on an EVC cross-connect and bridge domain service. REP is not supported for Ethernet Private Line and Ethernet Virtual Private Line services. |
REP does not support protection or loop prevention on ring interfaces which have one of the following EFP configurations:
Though a REP ring will converge with such interfaces, traffic loop can happen depending on the EVC configuration.
Using the REP over EVC feature, you can:
Restrictions for REP over EVC
- It is recommended that you begin by configuring one port and then configure the contiguous ports to minimize the number of segments and the number of blocked ports.
- REP is not supported on LACP.
- To avoid misconfiguration, you must configure all the trunk ports in the segment with the same set of allowed VLANs.
- Because REP blocks all VLANs until another REP interface sends a message to unblock it, you might lose connectivity to the port. This happens if you enable REP in a telnet session that accesses the EVC port through the same interface.
- On a device if REP is enabled on two ports for a segment, both ports must either be a regular segment ports or edge ports. REP ports follow these rules on a device:
- If only one port is configured in a segment, the port should be an edge port.
- If two ports belong to the same segment, both ports must be edge ports or the regular segment ports.
- If two ports belong to the same segment and one is configured as an edge port and other as a regular segment port, the edge port is treated as a regular segment port.
- There can be only two edge ports in a segment; if there are two edge devices in a segment, each device can have only one edge port. All the other ports on the edge device function as normal ports.
- REP interfaces come up in a blocked state and remains in a blocked state until notified that it is safe to unblock.
- REP relays all LSL Protocol Data Units (PDUs) in untagged frames and only HFL packets are relayed on the administrative VLAN.
- REP is not supported on EtherChannels. It is supported on EVC port-channels. REP is implemented on port-channels instead of its individual member links.
- In case of double VLAN tagged frame, REP is implemented only on the outer VLAN tag.
- When an edge no-neighbor is configured on a device, configuring and unconfiguring an edge port is not allowed.
- Configuring REP over EVC
- Configuring REP over EVC Using a Cross–Connect
- Configuring REP over EVC Using the Bridge Domain
- Verifying REP with EVC Configuration
Configuring REP over EVC
Perform any of the following procedures as needed:
Configuring REP over EVC Using a Cross–Connect
1.
enable
2.
configure terminal
3.
interface interface-id
4.
service instance id ethernet [evc-id]
5. encapsulation dot1q {any | vlan-id [vlan-id [-vlan-id]]} second-dot1q {any | vlan-id [vlan-id [-vlan-id]]}
6. rewrite ingress tag {push {dot1q vlan-id | dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | pop {1 | 2} | translate {1-to-1 {dot1q vlan-id | dot1ad vlan-id}| 2-to-1 dot1q vlan-id | dot1ad vlan-id}| 1-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | 2-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id}} {symmetric}
7.
rep segment segment-id [edge [no-neighbor] [primary]] [preferred]
8.
exit
DETAILED STEPS
| Command or Action | Purpose | |||||
|---|---|---|---|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. | ||||
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. | ||||
| Step 3 | interface interface-id Example: Switch(config)# interface TenGigabitEthernet 0/45
| Specifies the interface to configure and enters the interface configuration mode. | ||||
| Step 4 | service instance id ethernet [evc-id] Example: Switch(config-if)# service instance 101 ethernet
| Configures an Ethernet service instance on an interface and enters the service instance configuration mode. | ||||
| Step 5 | encapsulation dot1q {any | vlan-id [vlan-id [-vlan-id]]} second-dot1q {any | vlan-id [vlan-id [-vlan-id]]} Example: Switch(config-if-srv)# encapsulation dot1q 100 second-dot1q 200
| Configures the encapsulation. Defines the matching criteria to be used to map ingress dot1q frames on an interface to the appropriate service instance. | ||||
| Step 6 | rewrite ingress tag {push {dot1q vlan-id | dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | pop {1 | 2} | translate {1-to-1 {dot1q vlan-id | dot1ad vlan-id}| 2-to-1 dot1q vlan-id | dot1ad vlan-id}| 1-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | 2-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id}} {symmetric} Example:Switch(config-if-srv)# rewrite ingress tag dot1q single symmetric | Specifies the rewrite operation to be applied on the frame ingress to the service instance. | ||||
| Step 7 | rep segment segment-id [edge [no-neighbor] [primary]] [preferred] Example: Switch(config-if)# rep segment 3 edge
| Configures REP over EVC. The segment ID range is from 1 to 1024.
The following optional keywords are available.
| ||||
| Step 8 | exit Example: Switch(config-if)# exit
| Exits interface configuration mode. |
Configuring REP over EVC Using the Bridge Domain
1.
enable
2.
configure terminal
3.
interface interface-id
4.
service instance id ethernet [evc-id]
5. encapsulation dot1q {any | vlan-id [vlan-id [-vlan-id]]} second-dot1q {any | vlan-id [vlan-id [-vlan-id]]}
6. rewrite ingress tag {push {dot1q vlan-id | dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | pop {1 | 2} | translate {1-to-1 {dot1q vlan-id | dot1ad vlan-id}| 2-to-1 dot1q vlan-id | dot1ad vlan-id}| 1-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | 2-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id}} {symmetric}
7.
bridge-domain bridge-id [split-horizon]
8.
exit
9.
rep segment segment-id [edge [no-neighbor] [primary]] [preferred]
10.
exit
DETAILED STEPS
| Command or Action | Purpose | |||||
|---|---|---|---|---|---|---|
| Step 1 | enable Example: Switch> enable
| Enables privileged EXEC mode. | ||||
| Step 2 | configure terminal Example: Switch# configure terminal
| Enters global configuration mode. | ||||
| Step 3 | interface interface-id Example: Switch(config)# interface TenGigabitEthernet 0/45
| Specifies the interface to configure and enters interface configuration mode. | ||||
| Step 4 | service instance id ethernet [evc-id] Example: Switch(config-if)# service instance 101 ethernet
| Configures an Ethernet service instance on an interface and enters service instance configuration mode. | ||||
| Step 5 | encapsulation dot1q {any | vlan-id [vlan-id [-vlan-id]]} second-dot1q {any | vlan-id [vlan-id [-vlan-id]]} Example: Switch(config-if-srv)# encapsulation dot1q 100 second dot1q 200
| Configures the encapsulation. Defines the matching criteria to be used in order to map ingress dot1q frames on an interface to the appropriate service instance. | ||||
| Step 6 | rewrite ingress tag {push {dot1q vlan-id | dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | pop {1 | 2} | translate {1-to-1 {dot1q vlan-id | dot1ad vlan-id}| 2-to-1 dot1q vlan-id | dot1ad vlan-id}| 1-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id} | 2-to-2 {dot1q vlan-id second-dot1q vlan-id | dot1ad vlan-id dot1q vlan-id}} {symmetric} Example:Switch(config-if-srv)# rewrite ingress tag push dot1q 20 | Specifies the rewrite operation to be applied on the frame ingress to the service instance. | ||||
| Step 7 | bridge-domain bridge-id [split-horizon] Example: Switch(config-if-srv)# bridge-domain 10
| Configures the bridge domain to add another VLAN tag of type bridge-domain to the incoming packet. | ||||
| Step 8 | exit Example: Switch(config-if-srv)# exit
| Exits service instance configuration mode. | ||||
| Step 9 | rep segment segment-id [edge [no-neighbor] [primary]] [preferred] Example: Switch(config-if)# rep segment 2 edge primary
| Configures REP over EVC. The segment ID range is from 1 to 1024.
The following optional keywords are available.
| ||||
| Step 10 | exit Example: Switch(config-if)# exit
| Exits interface configuration mode. |
Example: Configure REP over EVC Using the Bridge Domain
The following example shows how to configure REP over EVC using the bridge domain.
Switch# enable Switch# configure terminal Switch(config)# interface TenGigabitEthernet 0/45 Switch(config-if)# service instance 10 ethernet Switch(config-if-srv)# encapsulation dot1q 10 Switch(config-if-srv)# rewrite ingress tag push dot1q 10 symmetric Switch(config-if-srv)# bridge-domain 100 Switch(config-if-srv)# exit Switch(config-if)# rep segment 2 edge Switch(config-if)# end
Verifying REP with EVC Configuration
You can use the show rep topology, show rep topology detail and show interface rep commands to verify REP over EVC configuration.
Example of the show rep topology Command
Switch# show rep topologyREP Segment 2 BridgeName PortName Edge Role ---------------- ---------- ---- ---- Edge Gi0/2 Pri Open ME2600X-2 Gi0/2 Open ME2600X-2 Gi0/1 Open ME2600X-1 Gi0/1 Open ME2600X-1 Gi0/3 Open Edge Gi0/3 Sec Alt
Example of the show rep topology detail Command
Switch# show rep topology detailREP Segment 2 Edge, Gi0/2 (Primary Edge) Open Port, all vlans forwarding Bridge MAC: 108c.8370.3000 Port Number: 005 Port Priority: 000 Neighbor Number: 1 / [-6] ME2600X-2, Gi0/2 (Intermediate) Open Port, all vlans forwarding Bridge MAC: 108c.8370.2000 Port Number: 005 Port Priority: 000 Neighbor Number: 2 / [-5] ME2600X-2, Gi0/1 (Intermediate) Open Port, all vlans forwarding Bridge MAC: 108c.8370.2000 Port Number: 004 Port Priority: 000 Neighbor Number: 3 / [-4] ME2600X-1, Gi0/1 (Intermediate) Open Port, all vlans forwarding Bridge MAC: 108c.8370.1000 Port Number: 004 Port Priority: 000 Neighbor Number: 4 / [-3] ME2600X-1, Gi0/3 (Intermediate) Open Port, all vlans forwarding Bridge MAC: 108c.8370.1000 Port Number: 006 Port Priority: 000 Neighbor Number: 5 / [-2] Edge, Gi0/3 (Secondary Edge) Alternate Port, some vlans blocked Bridge MAC: 108c.8370.3000 Port Number: 006 Port Priority: 010 Neighbor Number: 6 / [-1]
Example of the show interface rep detail Command
Switch# show interfaces gigabitEthernet 0/2 rep detailGigabitEthernet0/2 REP enabled Segment-id: 2 (Primary Edge) PortID: 0005108C83703000 Preferred flag: No Operational Link Status: TWO_WAY Current Key: 0006108C83703000E83D Port Role: Open Blocked VLAN: <empty> Admin-vlan: 4000 Preempt Delay Timer: disabled LSL Ageout Timer: 5000 ms LSL Ageout Retries: 5 Configured Load-balancing Block Port: none Configured Load-balancing Block VLAN: none STCN Propagate to: none LSL PDU rx: 139771, tx: 83514 HFL PDU rx: 12, tx: 6 BPA TLV rx: 71413, tx: 1049 BPA (STCN, LSL) TLV rx: 0, tx: 0 BPA (STCN, HFL) TLV rx: 0, tx: 0 EPA-ELECTION TLV rx: 45, tx: 38 EPA-COMMAND TLV rx: 0, tx: 0 EPA-INFO TLV rx: 19415, tx: 19415
REP with Multicast
REP supports up to 24 segments in each node.
In an REP ring, the multicast traffic may not flow across all the elements on the ring; the traffic depends on the path taken from the multicast device to the client. The elements that do not form the multicast path do not become members of the multicast group.
When there is a failure in an REP ring, it is possible that the new path between the multicast device and the client may traverse elements which were previously not part of the multicast traffic path. These elements do not forward multicast traffic till they see a query from multicast device and a join from the client. A multicast device may only send query after long intervals, which results in a large traffic hit. All the ports that are enabled with REP must be configured as static multicast device ports to solve this issue.