Users Guide

• When a stack reloads and all units come up at the same time (for example, when all units boot up from ash), all units participate
in the election. The master and standby are chosen based on the highest MAC address or (if congured) the highest priorities.
• When stack units do not boot up at the same time (for example, some units are powered down just after reloading and powered
up later to join the stack), the units that boot up later do not participate in the election process, even though these units may
have a higher priority congured. This happens because the master and standby have already been elected; therefore, the unit
that boots up late joins only as a member. To include late-booting units in the master election, reload the stack.
• When a stack or standalone unit that is up and running is merged with another stack, according to the master election, the losing
stack reloads and the master unit of the winning stack becomes the master of the merged stack.
Example of Viewing Stack Members
S5000-1#show system brief
Stack MAC : 5c:f9:dd:ef:06:00
Reload-Type : normal-reload [Next boot : normal-reload]
-- Stack Info --
Unit UnitType Status ReqTyp CurTyp Version
--------------------------------------------------
0 Member not present S5000
1 Standby online S5000 S5000 9-0-1-0
2 Management online S5000 S5000 9-0-1-0
3 Member not present S5000
4 Member not present S5000
5 Member not present
6 Member not present
7 Member not present
8 Member not present
9 Member not present
10 Member not present
11 Member not present
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 congure a virtual IP: Dell(conf)#virtual-ip {ip-address | ipv6–address |
dhcp}
Failover Roles
If the stack master fails (for example, is powered o), 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.
After the former master switch recovers, despite having a higher priority or MAC address, it does not recover its master role but
instead takes the next available role.
MAC Addressing
All port interfaces in the stack use the MAC address of the management interface on the master switch. The MAC address of the
chassis in which you use the master switch as the stack MAC address.
The stack continues to use the master’s chassis MAC address even after a failover. The MAC address is not refreshed until the stack
is reloaded and a dierent unit becomes the stack master.
NOTE: If the removed management unit is brought up as a standalone unit or as part of a dierent stack, there is a
possibility of MAC address collisions. If you add a standalone unit, which has the same priority as the master stack unit,
the standalone unit joins the stack as a member unit.
826
Stacking