Contents

Configuring Reth interfaces· 1

About Reth interfaces· 1

Operating mechanism·· 1

Restrictions and guidelines: Reth interface configuration· 2

Configuring a Reth interface· 2

Displaying and maintaining Reth interfaces· 3

Example: Configuring a Reth interface· 3

Configuring redundancy groups· 2

About redundancy groups· 2

Operating mechanism of a redundancy group· 2

Redundancy group node states· 2

Redundancy group members· 3

Redundancy group switchover 4

Redundancy group configuration tasks at a glance· 5

Creating a redundancy group· 5

Configuring a redundancy group node· 5

Assigning Reth interfaces to a redundancy group· 6

Configuring the switchover timers· 7

Performing a manual switchover to the low-priority node· 7

Performing a manual switchover back to the high-priority node· 8

Enabling SNMP notifications for redundancy groups· 8

Displaying and maintaining redundancy groups· 8

 

Configuring Reth interfaces

About Reth interfaces

A redundant Ethernet (Reth) interface is a virtual Layer 3 interface that uses two member interfaces to ensure link availability. The member interfaces are management Ethernet interfaces. As shown in Figure 1, M-GigabitEthernet 0/0/0 and M-GigabitEthernet 0/0/1 are member interfaces of Reth 1. M-GigabitEthernet 0/0/0 is active to forward traffic, and M-GigabitEthernet 0/0/1 is inactive. When M-GigabitEthernet 0/0/0 fails, M-GigabitEthernet 0/0/1 becomes active. The member interface switchover does not interrupt traffic.

Figure 1 Reth interface

 

Operating mechanism

A member interface of a Reth interface can be in either of the following states:

·     Active—The interface can forward packets. A Reth interface can have only one active member interface.

·     Inactive—The interface cannot forward packets.

A Reth interface determines the state of its member interfaces by using the following rules:

·     When the member interfaces are physically up, the member interface with the higher priority is active. The other member interface is inactive. The priority of an interface is user configurable.

·     When the member interfaces are physically down, both interfaces are inactive.

·     When the active member interface goes down physically, the inactive interface automatically becomes active to forward packets.

A Reth interface has only one active member interface.

A Reth interface uses the bridge MAC address, and you can assign an IP address to it. When a member interface receives a packet, it sends the packet to the Reth interface for processing. Then, the Reth interface sends the packet back to the member interface for forwarding.

The switchover between the Reth member interfaces is not visible to the network and does not cause network topology changes. For the upstream and downstream devices, they are connected to the Reth interface.

Restrictions and guidelines: Reth interface configuration

 

To use the Reth interface feature on an MPU, make sure it has a minimum of two management Ethernet interfaces.

After you assign a management Ethernet interface to a Reth interface, the IP address assigned to the management Ethernet interface is no longer effective. To log in to the device, visit the IP address of the Reth interface.

Configuring a Reth interface

1.     Enter system view.

system-view

2.     Create a Reth interface and enter its view.

interface reth interface-number

By default, no Reth interfaces exist.

3.     Assign a member interface to the Reth interface.

member interface interface-type interface-number priority priority

By default, a Reth interface does not have member interfaces.

4.     (Optional.) Configure the expected bandwidth for the Reth interface.

bandwidth bandwidth-value

By default, the expected bandwidth is 10000 kbps.

The expected bandwidth is an informational parameter used only by higher-layer protocols for calculation. You cannot adjust the actual bandwidth of an interface by using this command.

5.     (Optional.) Configure the description of the Reth interface.

description text

The default description of a Reth interface is interface-name Interface (for example, Reth1 Interface).

6.     (Optional.) Set the MTU of the Reth interface.

mtu size

By default, the MTU of a Reth interface is 1500 bytes.

7.     Bring up the Reth interface.

undo shutdown

The default of this command varies by device model.

Displaying and maintaining Reth interfaces

Execute display commands in any view and reset commands in user view.

 

Task	Command
Display information about the member interfaces of a Reth interface.	display reth interface interface-type interface-number
Display Reth interface information.	display interface [ reth [ interface-number ] ] [ brief [ description | down ] ]
Clear statistics for Reth interfaces.	reset counters interface [ reth [ interface-number ] ]

 

Example: Configuring a Reth interface

Network configuration

As shown in Figure 2, assign Internet-facing management Ethernet interfaces M-GigabitEthernet 0/0/0 and M-GigabitEthernet 0/0/1 to a Reth interface. Assign a high priority to M-GigabitEthernet 0/0/0 for it to be active.

Figure 2 Network diagram

 

Procecure

# Create Reth 1, and assign an IP address to it.

[Sysname] interface reth 1

[Sysname-Reth-1] ip address 1.0.0.3 24

# Assign M-GigabitEthernet 0/0/0 and M-GigabitEthernet 0/0/1 to Reth 1, and set their priority to 100 and 80, respectively.

[Sysname-Reth1] member interface M-GigabitEthernet0/0/0 priority 100

[Sysname-Reth1] member interface M-GigabitEthernet0/0/1 priority 80

Verifying the configuration

# Verify that M-GigabitEthernet 0/0/0 is active and M-GigabitEthernet 0/0/1 is inactive on Reth 1.

[Sysname-Reth1] display reth interface reth 1

Reth1 :

  Redundancy group  : N/A

  Member                    Physical status       Forwarding status    Presence status

  MGE0/0/0                UP                    Active               Normal

  MGE0/0/1                UP                    Inactive             Normal

# Shut down M-GigabitEthernet 0/0/0, and verify that M-GigabitEthernet 0/0/1 is active.

[Sysname-Reth1] quit

[Sysname] interface M-GigabitEthernet 0/0/0

[Sysname-M-GigabitEthernet 0/0/0] shutdown

[Sysname-M-GigabitEthernet 0/0/0] display reth interface reth 1

Reth1 :

  Redundancy group  : N/A

  Member                   Physical status         Forwarding status    Presence status

  MGE0/0/0               DOWN                    Inactive              Normal

  MGE0/0/1               UP                      Active                Normal

 

Configuring redundancy groups

About redundancy groups

A redundancy group works on IRF fabrics. It allows traffic to enter and leave an IRF fabric through the same member device.

Operating mechanism of a redundancy group

As shown in Figure 3, a redundancy group has two redundancy group nodes. Each node is bound to an IRF member device.

A redundancy group node is a collection of objects on its bound IRF member device. The objects are member interfaces of Reth interfaces. The state of the objects is consistent with the state of the node.

In a redundancy group, one node is in primary state, and the other node is in secondary state. Only the primary node forwards traffic. When the primary node fails, the redundancy group switches over to the secondary node. This mechanism ensures path symmetry for traffic.

As shown in Figure 3, a redundancy group performs a switchover as follows:

1.     When both IRF member devices are operating correctly, the redundancy group forwards traffic through Node 1 (Device A) and backs up services and data (such as NAT) to Node 2 (Device B).

2.     When the upstream interface on Device A fails, the redundancy group shuts down the downstream interface on Device A and switches traffic over to Device B.

Figure 3 Redundancy group operating mechanism

 

Redundancy group node states

A redundancy group node can act as the primary or secondary node. Only the primary node can forward traffic.

When both nodes are operating correctly, the primary node is selected in the following order:

1.     The node with higher node priority.

2.     The node with smaller ID if the two nodes have the same priority.

When the primary node fails, the secondary node takes over the primary role to forward traffic. For more information about the state monitoring and switchover mechanisms, see "Redundancy group switchover."

Redundancy group members

Application scenarios of redundancy group members

Redundancy group members are Reth interfaces. Reth interfaces are used when no dynamic routing protocol runs between the device and its upstream and downstream devices.

Using Reth interfaces in a redundancy group

To use Reth interfaces for symmetric forwarding, you must assign two Reth interfaces to a redundancy group: one for uplink traffic and the other for downlink traffic. The Reth interfaces must meet the following requirements:

·     The Reth interface for uplink traffic contains one uplink port on each redundancy group node.

·     The Reth interface for downlink traffic contains one downlink port on each redundancy group node.

·     The high-priority member of each Reth interface belongs to the high-priority node.

 The state of each Reth interface's members depends on the state of the redundancy group nodes.

·     When the high-priority node is in primary state, the high-priority member is active.

·     When the low-priority node is in primary state, the low-priority member is active.

As shown in Figure 4, redundancy group 1 contains Reth 1 for uplink traffic and Reth 2 for downlink traffic. Reth 1 contains Interface A1 (on Node 1) and Interface B1 (on Node 2). Reth 2 contains Interface A2 (on Node 1) and Interface B2 (on Node 2).

When Node 1 is in primary state, Interface A1 in Reth 1 and Interface A2 in Reth 2 are active to forward uplink and downlink traffic, respectively.

When Interface A1 fails, the Reth module places Node 1 in secondary state and shuts down Interface A2, as shown in Figure 5. Node 2 changes to the primary state, and Interface B1 and Interface B2 become active to forward uplink and downlink traffic.

Figure 4 States of each Reth interface's members when both nodes are operating correctly

 

Figure 5 States of each Reth interface's members after a switchover

 

Redundancy group switchover

Switchover types

Redundancy group switchovers include automatic switchovers and manual switchovers.

Automatic switchover timers

Timers for automatic switchovers include the hold-down timer and the preemption delay timer.

·     Hold-down timer—The hold-down timer specifies the minimum interval between two switchovers to prevent frequent switchovers. The timer starts when a switchover is finished. The redundancy group can perform the next switchover only after the hold-down timer expires.

·     Preemption delay timer—The preemption delay timer specifies the delay for a switchover back to the high-priority node. The preemption delay timer starts when the switchover is triggered. The redundancy group performs the switchover only after the timer expires. The delay allows the system to process events (such as interface state changes) required for the switchover.

Automatic switchover

A redundancy group cooperates with the Track module to monitor link and interface status for automatic switchovers.

A redundancy group node has a weight of 255 (not configurable). Each redundancy group node is associated with one or multiple track entries that have a user-configurable weight decrement rate. When the state of a track entry changes, the weight of the associated node is reduced or increased, as follows:

·     When the track entry changes to the NotReady or Negative state, the node weight is reduced by the weight decrement rate of the track entry.

·     When the track entry changes to the Positive state, the node weight is increased by the weight decrement rate of the track entry.

When the node weight decreases to 0 or a lower value, a switchover request is triggered.

·     Switchover to the low-priority node occurs when the hold-down timer expires.

·     Switchover to the high-priority node occurs when the preemption delay timer expires.

Manual switchover

You can issue a manual switchover request in one of the following situations:

·     An automatic switchover to the high-priority node cannot be performed when no tracked interfaces are excluded from the shutdown action by the Reth module.

·     Switchovers are required when both redundancy group nodes operate correctly. For example, component replacement is required on the high-priority node.

Manual and automatic switchovers to the high-priority node are not allowed if the preemption delay timer is set to 0, even when both nodes are operating correctly.

Redundancy group configuration tasks at a glance

To configure a redundancy group, perform the following tasks:

1.     Creating a redundancy group

2.     Configuring a redundancy group node

3.     Assigning Reth interfaces to a redundancy group

This task is applicable to the network scenario where no dynamic routing protocol runs between the IRF fabric and its upstream and downstream devices.

4.     (Optional.) Performing a manual switchover

5.     (Optional.) Performing a manual switchover back to the high-priority node

6.     (Optional.) Enabling SNMP notifications for redundancy groups

Creating a redundancy group

Restrictions and guidelines

If an IRF fabric contains a minimum of four member devices, you can configure multiple independent redundancy groups. These redundancy groups operate independently.

Before you delete a redundancy group, you must remove all its Reth interfaces and redundancy group nodes.

Procedure

1.     Enter system view.

system-view

2.     Create a redundancy group and enter its view.

redundancy group group-name

By default, no redundancy groups exist.

Configuring a redundancy group node

Restrictions and guidelines

You can configure a maximum of two nodes for a redundancy group. Nodes in different redundancy groups can use the same ID.

You can create only one-to-one bindings between redundancy group nodes and IRF member devices. You cannot change the binding for a node if it has member interfaces or is associated with track entries.

When you associate a track entry with a redundancy group node, follow these restrictions and guidelines:

·     You cannot associate a track entry with both nodes in a redundancy group.

·     For correct interface state recovery, you must exclude a tracked interface from the shutdown action by the Reth module if the interface has one of the following roles:

¡     Member interface in the redundancy group.

¡     Member of a Reth interface in the redundancy group.

·     On the high-priority node, do not exclude a subinterface from the shutdown action by the Reth module if its main interface has one of the following roles:

¡     Member interface of the redundancy group.

¡     Member of a Reth interface in the redundancy group.

When the Reth module shuts down the main interface, the subinterface is also shut down. The shutdown subinterface cannot recover automatically to trigger an automatic switchover.

Prerequisites

Before you associate a track entry with a redundancy group, you must configure the track entry. For more information about configuring track entries, see "Configuring Track."

Procedure

1.     Enter system view.

system-view

2.     Enter redundancy group view.

redundancy group group-name

3.     Create a redundancy group node and enter its view.

node node-id

By default, no redundancy group nodes exist.

4.     Set the priority of the redundancy group node.

priority priority

By default, the priority of a redundancy group node is 1.

5.     Bind the redundancy group node with an IRF member device.

bind chassis chassis-number

By default, a node is not bound with an IRF member device.

6.     Associate an existing track entry with the redundancy group node.

track track-entry-number [ reduced weight-reduced ] [ interface interface-type interface-number ]

By default, a node is not associated with track entries.

Assigning Reth interfaces to a redundancy group

Restrictions and guidelines

To use Reth interfaces for symmetric forwarding, you must assign two Reth interfaces to a redundancy group: one for uplink traffic and the other for downlink traffic. The Reth interfaces must meet the following requirements:

·     The Reth interface for uplink traffic contains one uplink port on each redundancy group node.

·     The Reth interface for downlink traffic contains one downlink port on each redundancy group node.

·     The high-priority member of each Reth interface belongs to the high-priority node.

Procedure

1.     Enter system view.

system-view

2.     Create a Reth interface and enter its view.

interface reth interface-number

3.     Assign a member interface to the Reth interface.

member interface interface-type interface-number priority priority

By default, a Reth interface does not have member interfaces.

Repeat this step to assign two member interfaces to the Reth interface. Assign a higher priority for the priority argument to the member interface on the high-priority redundancy node.

4.     Return to system view.

quit

5.     Enter redundancy group view.

redundancy group group-name

6.     Assign the Reth interface to the redundancy group.

member interface reth interface-number

By default, a redundancy group does not contain Reth interfaces.

Configuring the switchover timers

1.     Enter system view.

system-view

2.     Enter redundancy group view.

redundancy group group-name

3.     Set the hold-down timer for the redundancy group.

hold-down-interval second

By default, the hold-down timer is 1 second.

4.     Set the preemption delay timer for the redundancy group.

preempt-delay min

By default, the preemption delay timer is 1 minute.

If you set this timer to 0 seconds, manual and automatic switchovers to the high-priority node are disabled.

Performing a manual switchover to the low-priority node

1.     Enter system view.

system-view

2.     Enter redundancy group view.

redundancy group group-name

3.     Request a switchover to the low-priority node.

switchover request

Performing a manual switchover back to the high-priority node

1.     Enter system view.

system-view

2.     Enter redundancy group view.

redundancy group group-name

3.     Request a switchover back to the high-priority node.

switchover reset

Enabling SNMP notifications for redundancy groups

About this task

This feature enables SNMP notifications for the following events:

·     A manual switchover is performed.

·     An interface goes down.

·     A faulty interface is recovered.

To send the event notifications to an NMS, you must also configure SNMP as described in Network Management and Monitoring Configuration Guide.

Procedure

1.     Enter system view.

system-view

2.     Enable SNMP notifications for redundancy groups.

snmp-agent trap enable rddc

By default, SNMP notifications are enabled for redundancy groups.

Displaying and maintaining redundancy groups

Execute display commands in any view.

 

Task	Command
Display redundancy group information.	display redundancy group [ group-name ]