Hitless Stacking Configuration Notes And Feature Limitations; What Happens During A Hitless Stacking Switchover Or Failover; Real-Time Synchronization Among All Units In A Stack - Arris Ruckus ICX 7850 Series Configuration Manual

Hitless Stacking

Hitless stacking configuration notes and feature limitations

Hitless stacking configuration notes and feature
limitations
• Layer 3 multicast traffic is supported by hitless stacking.
• After a switchover or failover, the syslog may contain invalid (non-existent) port numbers in messages such as "Interface
portnum state up." This is because some messages from the old active controller remain in the syslog after a switchover
or failover.
• Failover for devices connected to the management port is not supported. For example, if during a failover, an end
station is connected to the stack through the management port of the active controller, the connection is shut down.
After the failover, the management port on the new active controller will work.
• The following describes hitless stacking limitations with software-based licensing for BGP:
– To enable BGP on a stack unit, you should have an appropriate BGP license installed on all the stack units.
– If the active controller has a BGP license but any other unit in the stack does not have one, you cannot enable BGP
on the stack unit.
– If the active controller is not running BGP, a stack unit is operational regardless of whether the active controller or
stack units have a BGP license.
– If the active controller is running BGP and a unit without a BGP license joins the stack, the unit is put into a non-
operational state. However, If the user installs a valid BGP license to a non-operational unit, the unit immediately
becomes operational. If the user disables BGP instead, the active controller returns the non-operational units to
operation.
What happens during a hitless stacking
switchover or failover
This section describes the internal events that enable a controlled or forced switchover to take place in a hitless manner as well
as the events that occur during the switchover.

Real-time synchronization among all units in a stack

Hitless stacking requires the active controller, standby controller, and stack members to be fully synchronized at all times. This is
accomplished by baseline and dynamic synchronization of all units in a stack.
When a stack is first booted and becomes operational, baseline synchronization occurs across all of the units in the stack. The
active controller copies the current state of its CPU to all units of the stack, including the standby controller. The information
received from the active controller is programmed locally in the hardware on all units. The information includes:
• Startup and runtime configuration (CLI) - These files are copied to the standby controller only.
• Layer 2 protocols - Layer 2 protocols such as STP, RSTP, MRP, and VSRP run concurrently on both the active controller
and standby controller.
• Hardware Abstraction Layer (HAL) - This includes the prefix-based routing table, next hop information for outgoing
interfaces, and tunnel information.
• Layer 3 IP forwarding information - This includes the routing table, IP cache table, and ARP table as well as static and
connected routes. Layer 3 routing protocols are not copied to any of the units in the stack but remain in standby state
on the standby controller until a switchover occurs. Peer adjacency is restored after a switchover. If BGP4 or OSPF
graceful restart is enabled during a switchover, the standby controller (new active controller) initiates a graceful restart,
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Ruckus FastIron Stacking Configuration Guide, 08.0.90
Part Number: 53-1005572-01