Dell PowerConnect W-IAP Remote Configuration Guide - Page 208

5 PowerConnect B-Series FCX hitless stacking (for example, a personal computer) pinging the stack might encounter a long delay depending on the client MAC aging time. The client won't work until it ages out the old MAC address and sends ARP requests to relearn the new stack MAC address. Refer to "Manual allocation of the IronStack MAC address" on page 120. • PBR is not supported by hitless stacking. When PBR is configured in an FCX IronStack, the stack will reload in the event of a failover. Also, manual switchover or internal switchover due to a higher priority standby is not allowed. • Layer 3 multicast traffic is not supported by hitless stacking. • After a switchover or failover, the Syslog may contain invalid (non-existent) port numbers in messages such as "Interface state up". This is because some messages from the old Active Controller will 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 will be 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: • If the Active Controller has a superior license (for example, BGP support) compared to all other units in the stack, all of the units except for the Active Controller will be placed in a non-operational state. • The Standby Controller cannot have a "superior" license compared to the Active Controller. For example, if unit 2 has a license to run BGP whereas the Active Controller does not, unit 2 has a superior license and will be allowed to join the stack, but will not be elected as the Standby Controller. • If software-based licensing is installed on the Active Controller after the stack is up and running, the licensed feature will function on the Active Controller ports, but will not function on ports on other units of the stack. 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 PowerConnect B-Series FCX units in a stack Hitless stacking requires that the Active Controller, Standby Controller, and stack members are fully synchronized at any given point in time. This is accomplished by baseline and dynamic synchronization of all units in a stack. When an PowerConnect B-Series FCX 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 hardware on all units. The information includes: • Start-up and run-time 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 and Standby Controller. 166 PowerConnect B-Series FCX Configuration Guide 53-1002266-01