Media Redundancy Protocol (MRP), defined in International Electrotechnical Commission (IEC) standard 62439-2, provides fast convergence in a ring network topology for Industrial Automation networks. MRP Media Redundancy Manager (MRM) defines its maximum recovery times for a ring in the following range: 10 ms, 30 ms, 200 ms and 500 ms.

Note	The default maximum recovery time on the Cisco IE switch is 200 ms for a ring composed of up to 50 nodes. You can configure the switch to use the 30 ms or the 500 ms recovery time profile as described in Configuring MRP Manager. The 10 ms recovery time profile is not supported.

MRP is supported on the following switches:

• Cisco Catalyst IE3x00 Rugged Series Switches (IE3200, IE3300, and IE3400)

• Cisco Catalyst IE3400 Heavy Duty Series Switches

• Cisco Catalyst IE3100 Rugged Series Switches (IE3100 and IE3105)

Note	MRP is not supported on Cisco Catalyst ESS3300 Switches.

MRP operates at the MAC layer and is commonly used in conjunction with the PROFINET standard for industrial networking in manufacturing.

There are two modes of MRP supported on the switch; however, only one mode can be enabled to operate on the switch at any given time:

• PROFINET MRP mode—Deployed in a PROFINET environment, the switch is added and managed by Siemens Totally Integrated Automation (TIA) Framework. This is the default MRP mode if the MRP manager or client license is activated through the web interface or command line.

  Note	When managing the switch with TIA, do not use the CLI or WebUI to configure MRP.

• MRP Command-line interface (CLI) mode—This mode is managed by the Cisco IOS CLI and WebUI, a web-based user interface (UI).

  Note	When managing the switch in MRP CLI mode, you cannot download the MRP configuration from Siemens STEP7/TIA.

In an MRP ring, the MRM serves as the ring manager, while the Media Redundancy Clients (MRCs) act as member nodes of the ring. Each node (MRM or MRC) has a pair of ports to participate in the ring. The MRM initiates and controls the ring topology to react to network faults by sending control frames on one ring port over the ring and receiving them from the ring over its other ring port, and conversely in the other direction. An MRC reacts to received reconfiguration frames from the MRM and can detect and signal link changes on its ring ports.

On Cisco Catalyst IE3x00 and IE3100 Rugged Series and IE3400 Heavy-Duty Switches, certain nodes or all nodes in the ring can also be configured to start as a Media Redundancy Automanager (MRA). MRAs select one MRM among each other by using a voting protocol and a configured priority value. The remaining MRAs transition to the MRC role.

All MRM and MRC ring ports support the following states:

• Disabled: Ring ports drop all received frames.

• Blocked: Ring ports drop all received frames except MRP control frames and some standard frames, for example, LLDP.

• Forwarding: Ring ports forward all received frames.

• Not Connected: The link is physically down or disconnected. (This state differs from the Disabled state, in which the MRP Port is manually disabled through software.)

During normal operation, the network operates in the Ring-Closed state (see figure below). To prevent a loop, one of the MRM ring ports is blocked, while the other port is forwarding. Most of the time, both ring ports of all MRCs are in the forwarding state. With this loop avoidance, the physical ring topology becomes a logical stub topology.

In the figure, note the following details about the two rings, left and right:

• Left Ring: The connection (small blue square, top) on the MRM is in a blocked state (as shown by the two parallel lines) because no ports are disconnected.

• Right Ring: Two MRC connections (left and center small white squares) are in the disabled state because the link between them is broken, as marked by a red “x”.

If a network failure occurs:

• The network shifts into the Ring-Open state.

• In the case of failure of a link connecting two MRCs, both ring ports of the MRM change to the forwarding state, the MRCs adjacent to the failure have a disabled and a forwarding ring port, and the other MRCs have both ring ports forwarding.

In the Ring-Open state, the network logical topology becomes a stub.

Layer 2 Ethernet frames will be lost during the time required for the transition between these two ring states. The MRP protocol defines the procedures to automatically manage the switchover to minimize the switchover time. A recovery time profile, composed of various parameters, drives the MRP topology convergence performance. The 200 ms profile supports a maximum recovery time of 200 ms.

MRP uses three types of control frames:

• To monitor the ring status, MRM regularly sends test frames on both ring ports.

• When MRM detects failure or recovery, it sends TopoChange frames on both ring ports.

• When MRC detects failure or recovery on a local port, it sends LinkChange subtype frames, Linkdown and Linkup, to the MRM.

Note	MRA can be activated through the CLI or through PROFINET.

If configured to start as a Media Redundancy Automanager (MRA), the node or nodes select an MRM using a voting protocol and configured priority value. The remaining MRAs transition to the MRC role. All nodes must be configured as MRA or MRC. A manually configured MRM and MRA in the same ring is not supported.

The MRA role is not an operational MRP role like MRM or MRC. It is only an administrative, temporary role at device startup, and a node must transition to the MRM role or the MRC role after startup and the MRM is selected though the manager voting process.

MRA functions as follows:

1. At power on, all MRAs begin the manager voting process. Each MRA begins to send MRP_Test frames on both ring ports. The MRP_Test frame contains the MRA's priority value. The remote manager's priority value contained in the received MRP_Test frames are compared with the MRA's own priority. If its own priority is higher than the received priority, the MRA sends a negative test manager acknowledgement (MRP_TestMgrNAck) frame, along with the remote manager's MAC address.

2. If the receiving MRA receives an MRP_TestMgrNAck with its own MAC address, the receiving MRA initiates the transition into the client (MRC) role.

3. The MRP_TestPropagate frame informs other MRA devices in the client role about the role change and the new higher priority manager. The clients receiving this frame update their higher priority manager information accordingly. This ensures that clients remain in the client role if the monitored higher priority manager role changes.

For information about the licensing packages for features available on Cisco Catalyst IE3x00 Rugged, IE3400 Heavy Duty, and ESS3300 Series Switches and Cisco Catalyst IE3100 Rugged Series Switches, see Licensing on the Cisco Catalyst IE3x00 and IE3100 Rugged, IE3400 Heavy Duty, and ESS3300 Series Switches.

In an Industrial Ethernet network, an MRP ring in a cell/area is a sub-ring of the access layer. You can connect multiple MRP rings, which you can then aggregate into the distribution layer.

Note	The MRP feature license requirement is removed in Cisco IOS XE 17.7.1 and later.

You can configure up to three rings, and you can configure the switch as either automanager or client.

MRP works with Spanning Tree Protocol (STP) to prevent unwanted broadcast loops in the event that a user accidentally connects a device that does not participate in the MRP ring. In a network operating with MRP and STP, spanning tree BPDUs are not sent on MRP-enabled ports. If ports are unconfigured from an MRP ring, then the ports are added to the spanning tree.

MRP-STP interoperability is supported for both PROFINET MRP mode and MRP CLI mode, and functions without additional CLI configuration.

• MRP is supported on Cisco Catalyst IE3x00 and IE3100 Rugged Series and IE3400 Heavy Duty Series Switches. MRP is not supported on ESS3300 Switches.

• In Cisco IOS XE 17.7.1 and later, the MRP feature is available as a part of Network Essentials Licensing. In releases prior to Cisco IOS XE 17.7.1, use of MRP requires a feature license that must be activated using the Cisco switch CLI.

• By default, Profinet MRP mode is enabled on Cisco Catalyst IE3x00 switches. You can configure MRP, including the MRP role, using the Cisco switch CLI only after you disable the PROFINET MRP function using the Cisco switch CLI.

  Note	Profinet MRP mode is not supported by default on Cisco Catalyst IE3x00 switches. You must use the Cisco switch CLI for configuration.

  When PROFINET MRP is enabled, use STEP7 and TIA to configure MRP, including the MRP role.

• To avoid Smart License registration failure, ensure that the NTP configuration and the device clock are in sync.

• With the MRP manager license (Cisco IOS XE 17.6.x and earlier), you can configure up to three rings on a device (each MRP instance can be manager or client), with a manager instance for each ring.

• Support for multiple MRP rings is available only through the CLI or WebUI.

• The switch supports up to 50 MRCs per ring.

• MRP cannot run on the same interface (port) as Resilient Ethernet Protocol (REP), Spanning Tree Protocol (STP), Flex Links, macsec, or Dot1x.

• STP does not run on MRP segments. MRP interfaces drop all STP BPDUs.

• For access ports, you must specifically configure switchport mode access and switchport access vlan x commands in the MRP interface.

• MRP interfaces come up in a forwarding state and remain in a forwarding state until notified that it is safe to block. The MRP ring state changes to Ring-Closed.

• MRP ports cannot be configured as any of these port types: SPAN destination port, Private VLAN port, or Tunnel port. Additionally, when operating in PROFINET mode, you cannot configure MRP ports as Trunk ports.

• MRP is not supported on EtherChannels or on an individual port that belongs to an EtherChannel.

• Each MRP ring can have one MRP VLAN. The VLAN must be different for each ring in a device to avoid traffic flooding.

PROFINET MRP Mode Only

• PROFINET MRP mode is supported on IE3x00 Series Switches; it is not supported on IE3100 Rugged Series Switches.

• Ensure that you configure the correct ring ID on client and manager. Ring ID configuration is not automatically validated by the switch.

• You can configure only one MRP ring in PROFINET MRP mode.

  Note	The number of MRP rings displayed in the show profinet status command output indicates the maximum number of rings allowed for configuration through the CLI and not through PROFINET.

• In PROFINET MRP, which is managed by STEP7 and TIA, only Layer 2 access ports are supported because PROFINET does not have the concept of VLAN tagging.

• The 10 ms profile is not supported.

• When using PROFINET MRP mode, we recommend setting the LLDP timer to 5 ms or 10 ms to ensure PROFINET can see neighbor devices and to avoid a Siemens PLC timeout.

• When a new pluggable module GSD file is installed in TIA/ STEP7, you must recreate the project in TIA/Step7. The existing project, which was created using the old GSD file, will display an error when you attempt to select the new GSD file for the same device. This occurs because the combo ports in the pluggable module SKUs were previously defined as fixed ports.

• You cannot change the role of any node from MRA to MRC after all nodes come up in MRA mode, either by breaking the ring (by shutting the port or physically removing the cable) or manually configuring the role change. If you want an MRP ring configuration with MRA and MRCs, you need to initially configure only one node as MRA and the rest as MRCs.

MRP CLI Mode Only

• After using the CLI to configure the MRP ring, you must attach the MRP ring to a pair of ports that support MRP.

• Both MRP ports must have the same interface mode (access or trunk).

• To change an existing MRP ring's configuration (mode), or to change the interface mode of the ring ports between access and trunk, you must first delete the ring and then recreate it with the new configuration.

• When both MRP ports are in access mode, the access VLANs should match. If the configured MRP VLAN does not match the ports' access VLAN, the MRP VLAN is automatically changed to the MRP ports’ access VLAN.

• In an MRP ring with two access ports, if the ports do not belong to the same access VLAN when you create the MRP ring or you change the access VLAN for only one of the ports after the MRP ring is created, the MRP ring operation is suspended and a message similar to the following is displayed:

  
  ERROR% The ring 1 ports don't belong to the same access VLAN. The MRP ring will not function until the issue has been fixed
  

  Resolve the issue by configuring the access VLAN to be the same for the two ring ports.

• The 200 ms standard profile, 500 ms profile, and 30 ms profile are supported. The 10 ms profile is not supported.

• MRA can be activated through CLI and PROFINET.

• In Cisco IOS XE 17.6.x and earlier, MRM and MRC licenses are not installed by default. Starting with 17.7.1 a feature license is no longer required for MRP.

• (Cisco IOS XE 17.6.x and earlier) PROFINET MRP mode is enabled by default when MRM or MRC licenses are enabled.

• MRP is disabled by default.

• The default VLAN is 1.

• Create the non-default VLAN before you assign it to MRP ring 1.

From IOS XE 17.18.1 onwards, Precision Time Protocol (PTP) is supported over Media Redundancy Protocol (MRP).

PTP is a time synchronization protocol for nodes distributed across a network. It is now supported over MRP according to IEC standard 62439-2 to achieve fast convergence in ring network topology for Industrial Automation networks.

PTP over MRP is supported on:

• IE3100-Manager, having 12 rings, with each ring consisting of 20 nodes spanning over a length of 20kms.

• Network using QoS (COS 6 / DSCP EF 46).

• Copper and SFP ports.

• Time error deviation of less than 10 microseconds at 50% link utilization between the head end and the host in case of an MRP ring break.

The PTP over MRP supported configurations are:

To configure MRP, configure the node as MRA or MRC, and specify the two MRP ports. With the mrp-manager license, you can configure up to three rings on the device (the device can be manager or client) with a manager instance for each ring and one manager per device. Each ring with a single MRM can support up to 50 MRCs.

Note	The MRP feature license (mrp-manager or mrp-client) applies only to Cisco IOS XE releases earlier than 17.7.1. Use of MRP in Cisco IOS XE 17.7.1 and later does not require a feature license, only the Network Essentials Base license.

The following MRP configuration parameters are optional except for domain-id, which is required for multiple MRP rings, and priority:

• domain-id—A unique ID that represents the MRP ring.

• domain-name—Logical name of the configured MRP domain-ID.

• profile—200 ms (the default)

• vlan-id—VLAN for sending MRP frames.

• default—In global MRP configuration, sets the mode to client.

The following example shows the MRP switch configured as manager:

Switch#configure terminal
Switch# no profinet mrp
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#mrp ring 1
Switch(config-mrp)#mode manager
Switch(config-mrp-manager)#end
Switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#interface gi1/8
Switch(config-if)#switchport mode trunk
Switch(config-if)#mrp ring 1
WARNING% Enabling MRP automatically set STP FORWARDING. It is recommended to shutdown all interfaces which are not currently in use to prevent potential bridging loops.
Switch(config-if)#exit
Switch(config)#interface gi1/7
Switch(config-if)#switchport mode trunk
Switch(config-if)#mrp ring 1
WARNING% Enabling MRP automatically set STP FORWARDING. It is recommended to shutdown all interfaces which are not currently in use to prevent potential bridging loops.
Switch(config-if)#end
 
Switch#show mrp ring
MRP ring 1
 
Profile     : 200 ms
Mode        : Master
From        : CLI
 
Network Topology: Ring
Port1:                                     Port2:
MAC Address    :2C:54:2D:2C:3E:0A          MAC Address    :2C:54:2D:2C:3E:09
Interface      :gigabitEthernet1/8            Interface      :gigabitEthernet1/7
Status         :Forwarding                 Status         :Forwarding
 
VLAN ID     : 1
Domain Name : Cisco MRP
Domain ID   : FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF
 
Topology Change Request Interval        : 10ms
Topology Change Repeat Count            : 3
Short Test Frame Interval               : 10ms
Default Test Frame Interval             : 20ms
Test Monitoring Interval Count          : 3
Test Monitoring Extended Interval Count : N/A
Switch#show mrp ports
 
Ring ID : 1
PortName                Status
--------------------------------------
gigabitEthernet1/7         Forwarding
gigabitEthernet1/8         Forwarding
 

The following example shows the MRP switch configured as automanager:

Switch#configure terminal
Switch# no profinet mrp
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#mrp ring 1
Switch(config-mrp)#mode auto-manager
Switch(config-mrp-auto-manager)#priority 36864
Switch(config-mrp-auto-manager)#end
Switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#interface gi1/2
Switch(config-if)#switchport mode trunk
Switch(config-if)#mrp ring 1
WARNING% Enabling MRP automatically set STP FORWARDING. It is recommended to shutdown all interfaces which are not currently in use to prevent potential bridging loops.
Switch(config-if)#exit
Switch(config)#interface gi1/1
Switch(config-if)#switchport mode trunk
Switch(config-if)#mrp ring 1
WARNING% Enabling MRP automatically set STP FORWARDING. It is recommended to shutdown all interfaces which are not currently in use to prevent potential bridging loops.
Switch(config-if)#end
 
Switch#show mrp ring
MRP ring 1

Profile     : 200 ms
Mode        : Auto-Manager
Priority    : 36864
Operational Mode: Manager
From        : CLI
License     : Active
Best Manager MAC Address    :84:B8:02:ED:E8:01     priority 36864     

Network Topology: Ring
Network Status  : OPEN
Port1:                                     Port2:
 MAC Address    :84:B8:02:ED:E8:02          MAC Address    :84:B8:02:ED:E8:01
 Interface      :GigabitEthernet1/2         Interface      :GigabitEthernet1/1
 Status         :Forwarding                 Status         :Forwarding

VLAN ID     : 1
Domain Name : Cisco MRP Ring 1
Domain ID   : FFFFFFFF-FFFF-FFFF-FFFF-FFFFFFFFFFFF

Topology Change Request Interval        : 10ms
Topology Change Repeat Count            : 3
Short Test Frame Interval               : 10ms
Default Test Frame Interval             : 20ms
Test Monitoring Interval Count          : 3
Test Monitoring Extended Interval Count : N/A

          
Topology Change Request Interval        : 10ms
Topology Change Repeat Count            : 3
Short Test Frame Interval               : 10ms
Default Test Frame Interval             : 20ms
Test Monitoring Interval Count          : 3
Test Monitoring Extended Interval Count : N/A

The following example shows the MRP switch configured as client:

Switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#mrp ring 1
Switch(config-mrp)#mode client
Switch(config-mrp-client)#end
Switch#configure terminal
Enter configuration commands, one per line. End with CNTL/Z.
Switch(config)#interface gi1/3
Switch(config-if)#switchport mode trunk
Switch(config-if)#mrp ring 1
Switch(config-if)#exit
Switch(config)#interface gi1/4
Switch(config-if)#switchport mode trunk
Switch(config-if)#mrp ring 1
Switch(config-if)#end