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Example: Configuring Interfaces for Uplink Failure Detection

Requirements

This example uses the following software and hardware components:

• Junos OS Release 12.1 or later for the QFX Series
• Two QFX3500 switches
• Two aggregation switches
• One dual-homed server

Overview and Topology

The topology in this example illustrates how to configure uplink failure detection on Switch A and Switch B. Switch A and Switch B are both configured with a link-to-monitor interface (the uplink interface to the aggregation switch) and a link-to-disable interface (the downlink interface to the server). For simplicity, only one group of link-to-monitor interfaces and link-to-disable interfaces is configured for each switch. The server is dual-homed to both Switch A and Switch B. In this scenario, if the link-to-monitor interface to Switch A is disabled, the server uses the link-to-monitor interface to Switch B instead.

Note: This example does not describe how to configure the dual-homed server or the aggregation switches. Please refer to the documentation for each of these devices for more information.

Figure 1 illustrates a typical setup for uplink failure detection.

Figure 1: Uplink Failure Detection Configuration on Switches

Table 1 lists uplink failure settings for each QFX3500 switch.

Configuring Uplink Failure Detection on Both Switches

To configure uplink failure detection on both switches, perform these tasks:

CLI Quick Configuration

To quickly configure uplink failure protection on Switch A and Switch B, copy the following commands and paste them into the switch terminal window:

Step-by-Step Procedure

1. Specify a name for the uplink failure detection group on Switch A:
   [edit protocols]
user@switch# set uplink-failure-detection group group1
2. Add an uplink interface to the group on Switch A:
   [edit protocols]
user@switch# set uplink-failure-detection group group1 link-to-monitor xe-0/0/0
3. Add a downlink interface to the group on Switch A:
   [edit protocols]
user@switch# set uplink-failure-detection group group1 link-to-disable xe-0/0/1
4. Specify a name for the uplink failure detection group on Switch B:
   [edit protocols]
user@switch# set uplink-failure-detection group group2
5. Add an uplink interface to the group on Switch B:
   [edit protocols]
user@switch# set uplink-failure-detection group group2 link-to-monitor xe-0/0/0
6. Add a downlink interface to the group on Switch B:
   [edit protocols]
user@switch# set uplink-failure-detection group group2 link-to-disable xe-0/0/1

Results

Display the results of the configuration:

Verification

To verify that uplink failure detection is working correctly, perform the following tasks on Switch A and Switch B:

• Verifying That Uplink Failure Detection is Working Correctly

Verifying That Uplink Failure Detection is Working Correctly

Purpose

Verify that the switch disables the downlink interface when it detects an uplink failure.

Action

1. View the current uplink failure detection status:
   user@switch> show uplink-failure-detection

   Group                     : group1
   Uplink                    :  xe-0/0/0*
   Downlink                  :  xe-0/0/1*
   Failure Action            :  Inactive
   

   Note: The asterisk (*) indicates that the link is up.

2. Disable the uplink interface:
   [edit]
user@switch# set interface xe-0/0/0 disable
3. Save the configuration on the switch.
4. View the current uplink failure detection status:
   user@switch> show uplink-failure-detection

   Group                     : group1
   Uplink                    :  xe-0/0/0
   Downlink                  :  xe-0/0/1
   Failure Action            :  Active
   

Meaning

The output in Step 1 shows that the uplink interface is up, and hence that the downlink interface is also up, and that the status of Failure Action is Inactive.

The output in Step 4 shows that both the uplink and downlink interfaces are down (there are no asterisks after the interface name) and that the status of Failure Action is changed to Active. This output shows that uplink failure detection is working.