Uplink Failure Detection on Switches
SUMMARY This section describes the uplink failure detection that allows Juniper Networks EX Series and QFX Series Ethernet Switches to detect link failure on uplink interfaces and to propagate the failure to the downlink interfaces so that servers connected to those downlink interfaces can switch over to secondary interfaces.
Understanding Uplink Failure Detection
Uplink failure detection supports network adapter teaming and provides network redundancy. In network adapter teaming, all the network interface cards (NICs) on a server are configured in a primary or secondary relationship and share the same IP address. When the primary link goes down, the server transparently shifts the connection to the secondary link. With uplink failure detection, the switch monitors uplink interfaces for link failures. When it detects a failure, it disables the downlink interfaces. When the server detects disabled downlink interfaces, it switches over to the secondary link to help ensure balanced traffic flow on switches.
This topic describes:
Uplink Failure Detection Overview
Uplink failure detection allows switches to monitor uplink interfaces to spot link failures. When a switch detects a link failure, it automatically disables the downlink interfaces in that group. The server that is connected to the disabled downlink interfaces triggers a network-adapter failover to a secondary link to avoid any information drop.
Figure 1 illustrates a typical setup for uplink failure detection.
For uplink failure detection, you specify a group of uplink interfaces to be monitored and downlink interfaces to be brought down when an uplink fails. The downlink interfaces are bound to the uplink interfaces within the group. If all uplink interfaces in a group go down, then the switch brings down all downlink interfaces within that group. If any uplink interface returns to service, then the switch brings all downlink interfaces in that group back to service.
Routed VLAN interfaces (RVIs) cannot be configured as uplink interfaces to be monitored.
The switch can monitor both physical-interface links and logical-interface links for uplink failures, but you must put the two types of interfaces in separate groups.
To detect failure of logical interfaces, the server must run some high level protocol such as keepalives between the switch and the server.
Failure Detection Pair
Uplink failure detection requires that you create groups that contain uplink interfaces and downlink interfaces. Each group includes one of each of the following:
-
A link-to-monitor interface—The link-to-monitor interfaces specify the uplink interfaces the switch monitors. You can configure a maximum of 48 uplink interfaces as link-to-monitor in a group.
A link-to-disable interface—The link-to-disable interfaces specify the downlink interfaces the switch disables when the switch detects an uplink failure. You can configure a maximum of 48 downlink interfaces as link-to-disable in a group.
The link-to-disable interfaces are bound to the link-to-monitor interfaces within the group. When a link-to-monitor interface returns to service, the switch automatically enables all link-to-disable interfaces in the group.
In QFX5120 and QFX5210 Series switches, you can configure a maximum of 128 uplink interfaces as link-to-monitor and a maximum of 128 downlink interfaces as link-to-disable.
Configuring Interfaces for Uplink Failure Detection (CLI Procedure)
You can configure uplink failure detection on EX Series and QFX Series switches to help ensure balanced traffic flow. Using this feature, switches can monitor and detect link failure on uplink interfaces and can propagate the failure to downlink interfaces so that servers connected to those downlink interfaces can switch over to secondary interfaces.
Follow these configuration guidelines:
-
You can configure a maximum of 48 groups for each switch.
-
You can configure a maximum of 48 uplink interfaces and 48 downlink interfaces in each group.
-
You can configure physical links and logical links in separate groups.
-
Ensure that all the interfaces in the group are up. If the interfaces are down, uplink failure detection does not work.
Routed VLAN interfaces (RVIs) cannot be configured as uplink interfaces to be monitored.
To configure uplink failure detection on a switch:
After you have configured a group, use the show uplink-failure-detection group group-name command to verify that all interfaces in the group are up.
Verifying That Uplink Failure Detection Is Working Correctly
Purpose
Verify that the switch disables the downlink interface when it detects an uplink failure.
Action
View the current uplink-failure-detection status:
user@switch> show uplink-failure-detection Group : group1 Uplink : ge-0/0/0* Downlink : ge-0/0/1* Failure Action : Inactive
Note:The asterisk (*) indicates that the link is up.
Disable the uplink interface:
[edit] user@switch# set interface ge-0/0/0 disable
Save the configuration on the switch.
View the current uplink-failure-detection status:
user@switch> show uplink-failure-detection Group : group1 Uplink : ge-0/0/0 Downlink : ge-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 and that the status of Failure
Action is changed to Active. This output shows that uplink failure detection is working.