Hitless Behavior; Graceful Restart - Dell S4820T Configuration Manual

-- Unit 1 --
Unit Type
Status
Required Type
Dell#
Dell(conf)#interface tengigabitethernet 1/0
Dell(conf-if-te-1/0)#
Removing a Provisioned Logical Stack Unit
To remove the line card configuration, use the following command.
• To remove a logical stack-unit configuration, use the following command:
CONFIGURATION mode
no stack-unit unit_id provision

Hitless Behavior

Hitless behavior is supported only on the S4820T platform.
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 defined 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 first (OSPF) is configured 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 flaps upon an RPM failover.
The following protocols are hitless:
• Link aggregation control protocol.
• Spanning tree protocol. Refer to

Graceful Restart

Graceful restart is supported on the S4820T platform.
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 specified 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.
404
: Member Unit
: not present
: S4820T - 52-port GE/TE/FG (SE)
Configuring Spanning Trees as Hitless.
High Availability (HA)