Hot Links; Forward Delay; Preemption; Fdb Update - IBM RackSwitch G8000 Application Manual

Hot Links

Forward Delay

Preemption

FDB Update

Configuration Guidelines

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RackSwitch G8000: Application Guide
For network topologies that require Spanning Tree to be turned off, Hot Links
provides basic link redundancy with fast recovery.
Hot Links consists of up to 200 triggers. A trigger consists of a pair of layer 2
interfaces, each containing an individual port, trunk, or LACP adminkey. One
interface is the Master, and the other is a Backup. While the Master interface is set
to the active state and forwards traffic, the Backup interface is set to the standby
state and blocks traffic until the Master interface fails. If the Master interface fails,
the Backup interface is set to active and forwards traffic. Once the Master interface
is restored, it transitions to the standby state and blocks traffic until the Backup
interface fails.
You may select a physical port, static trunk, or an LACP adminkey as a Hot Link
interface.
The Forward Delay timer allows Hot Links to monitor the Master and Backup
interfaces for link stability before selecting one interface to transition to the active
state. Before the transition occurs, the interface must maintain a stable link for the
duration of the Forward Delay interval.
For example, if you set the Forward delay timer to 10 seconds, the switch will select
an interface to become active only if a link remained stable for the duration of the
Forward Delay period. If the link is unstable, the Forward Delay period starts again.
You can configure the Master interface to resume the active state whenever it
becomes available. With Hot Links preemption enabled, the Master interface
transitions to the active state immediately upon recovery. The Backup interface
immediately transitions to the standby state. If Forward Delay is enabled, the
transition occurs when an interface has maintained link stability for the duration of
the Forward Delay period.
Use the FDB update option to notify other devices on the network about updates to
the Forwarding Database (FDB). When you enable FDB update, the switch sends
multicasts of addresses in the forwarding database (FDB) over the active interface,
so that other devices on the network can learn the new path. The Hot Links FBD
update option uses the station update rate to determine the rate at which to send
FDB packets.
The following configuration guidelines apply to Hot links:
• Ports that are configured as Hot Link interfaces must have STP disabled.
• When Hot Links is turned on, MSTP, RSTP, and PVRST must be turned off.
• When Hot Links is turned on, UplinkFast must be disabled.
• A port that is a member of the Master interface cannot be a member of the
Backup interface. A port that is a member of one Hot Links trigger cannot be a
member of another Hot Links trigger.
• An individual port that is configured as a Hot Link interface cannot be a member
of a trunk.