Administrator Guide
Example of Viewing a Logical Conguration of a Pre-Congured Stack Unit
After creating the logical stack unit, you can congure the interfaces on the stack unit as if it is present.
Removing a Provisioned Logical Stack Unit
To remove the line card conguration, use the following command.
• To remove a logical stack-unit conguration, use the following command:
CONFIGURATION mode
no stack-unit unit_id provision
Hitless Behavior
Hitless is a protocol-based system behavior that makes a stack unit failover on the local system transparent to remote systems. The system
synchronizes protocol information on the Management and Standby stack units such that, in the event of a stack unit failover, it is not
necessary to notify the remote systems of a local state change.
Hitless behavior is dened in the context of a stack unit failover only.
• Only failovers via the CLI are hitless. The system is not hitless in any other scenario.
Hitless protocols are compatible with other hitless and graceful restart protocols. For example, if hitless open shortest path rst (OSPF) is
congured over hitless the link aggregation control protocol (LACP) link aggregation groups (LAGs), both features work seamlessly to
deliver a hitless OSPF-LACP result. However, to achieve a hitless end result, if the hitless behavior involves multiple protocols, all protocols
must be hitless. For example, if OSPF is hitless but bidirectional forwarding detection (BFD) is not, OSPF operates hitlessly and BFD aps
upon an RPM failover.
The following protocols are hitless:
• Link aggregation control protocol.
• Spanning tree protocol. Refer to Conguring Spanning Trees as Hitless.
Graceful Restart
Graceful restart (also known as non-stop forwarding) is a protocol-based mechanism that preserves the forwarding table of the restarting
router and its neighbors for a specied period to minimize the loss of packets. A graceful-restart router does not immediately assume that a
neighbor is permanently down and so does not trigger a topology change. Packet loss is non-zero, but trivial, and so is still called hitless.
Dell Networking OS supports graceful restart for the following protocols:
• Border gateway
• Open shortest path rst
• Protocol independent multicast — sparse mode
• Intermediate system to intermediate system
High Availability (HA)
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