Users Guide

250 Stacking
Switch Stack MAC Addressing and Stack Design Considerations
The switch stack uses the MAC addresses assigned to the stack master.
If the backup unit assumes control due to a stack master failure or warm
restart, the backup unit continues to use the original stack master’s MAC
addresses. This reduces the amount of disruption to the network because
ARP and other layer-2 entries in neighbor tables remain valid after the failover
to the backup unit.
DOT1S Spanning tree port roles, port states, root bridge, etc.
802.1X Authenticated clients
DOT3ad Port states
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 four consecutive MAC addresses. A stack of
switches uses the MAC addresses assigned to the stack master.
Table 9-1. Applications that Checkpoint Data
Application Checkpointed Data