Stack Master Election; Virtual Ip; Failover Roles - Dell S3048-ON Configuration Manual

• Inter-switch stacking link failure
• Switch insertion
• Switch removal
If the master switch goes off line, the standby replaces it as the new master and the switch with the next highest priority or MAC address
becomes standby.

Stack Master Election

The stack elects a master and standby unit at bootup time based on two criteria.
• Unit priority — User-configurable. The range is from 1 to 14. A higher value (14) means a higher priority. The default is 0. By removing
the stack-unit priority using the no stack-unit priority command, you can set the priority back to the default value of zero.
The unit with the highest priority is elected the master management unit; the unit with the second highest priority is elected the
standby unit.
• MAC address (in case of priority tie) — The unit with the higher MAC value becomes the master unit. The stack takes the MAC
address of the master unit and retains it unless it is reloaded.
To view which switch is the stack master, enter the show system command.
A change in the stack master occurs when:
• You power down the stack master or bring the master switch offline.
• A failover of the master switch occurs.
• You disconnect the master switch from the stack.
When a stack reloads and all the units come up at the same time; for example, when all units boot up from flash, all units participate in the
election and the master and standby are chosen based on the priority or MAC address.
When the units do not boot up at the same time, such as when some units are powered down just after reloading and powered up later to
join the stack, they do not participate in the election process even though the units that boot up late may have a higher priority configured.
This happens because the master and standby have already been elected, hence the unit that boots up late joins only as a member.
When an up and running standalone unit or stack is merged with another stack, based on election, the losing stack reloads and the master
unit of the winning stack becomes the master of the merged stack. For more details, see
Remove a Unit from a Stack. It is possible to reset individual units to force them to give up the management role or reload the whole stack
from the CLI to ensure a fully synchronized bootup.
Example of Viewing Stack Members

Virtual IP

You can manage the stack using a single IP, known as a virtual IP, that is retained in the stack even after a failover.
The virtual IP address is used to log in to the current master unit of the stack. Both IPv4 and IPv6 addresses are supported as virtual IPs.
Use the following command to configure a virtual IP: Dell(conf)#virtual-ip {ip-address | ipv6–address | dhcp}

Failover Roles

If the stack master fails (for example, is powered off), it is removed from the stack topology.
The standby unit detects the loss of peering communication and takes ownership of the stack management, switching from the standby
role to the master role. The distributed forwarding tables are retained during the failover, as is the stack MAC address. The lack of a
standby unit triggers an election within the remaining units for a standby role.
sectionsAdd Units to an Existing Stack and
Stacking 801