Dell POWEREDGE M1000E - Manual (Page 145)

Managing a Switch Stack 145
Switch Stack MAC Addressing and Stack Design Considerations
The switch stack uses the MAC addresses assigned to the master unit.
If the backup unit assumes control due to a master unit failure or warm
restart, the backup unit continues to use the original master unit’s MAC
addresses. This reduces the amount of disruption to the network because
ARP and other L2 entries in neighbor tables remain valid after the failover to
the backup unit.
Stack units should always be connected with a ring topology (or other
biconnected topology), so that the loss of a single stack link does not divide
the stack into multiple stacks. If a stack is partitioned such that some units
lose all connectivity to other units, then both parts of the stack start using the
same MAC addresses. This can cause severe problems in the network.
IGMP/MLD Snooping Multicast groups, list of router ports, last query data for
each VLAN
IPv6 NDP Neighbor cache entries
iSCSI Connections
LLDP List of interfaces with MED devices attached
OSPFv2 Neighbors and designated routers
OSPFv3 Neighbors and designated routers
Route Table Manager IPv4 and IPv6 dynamic routes
SIM The system's MAC addresses. System up time. IP address,
network mask, default gateway on each management
interface, DHCPv6 acquired IPv6 address.
Voice VLAN VoIP phones identified by CDP or DHCP (not LLDP)
NOTE: Each switch is assigned three consecutive MAC addresses. The switch
uses the MAC addresses for the service port, network port, and routing
interfaces. A stack of switches uses the MAC addresses assigned to the master
unit.
Table 8-1. Applications that Checkpoint Data
Application Checkpointed Data