Specifications

D-Link xStack Switch Series: Meeting the Need at the Edge of the Network 16
D-Link Systems, Inc.
October 2004
When connected to a group, each switch will use the stack IP address. When a new master is
elected, it uses this IP address to continue interacting with the network.
Stack Creation and Modification
Stacks are created when individual switches are joined together with stacking cables. When the
stack ports detect electromechanical activity, each port starts to transmit information about its
switch. When the complete set of switches is known, the stack elects one of the members to be
the master switch, which will be responsible for maintaining and updating configuration files,
routing information, and other stack information. The entire stack will have a single IP address
that will be used by all the switches.
Master Redundancy
Master redundancy allows each stack member to serve as a master, providing the highest
reliability for forwarding. Each switch in the stack can serve as a master, creating a 1:N
availability scheme for network control. In the unlikely event of a single unit failure, all other
units continue to forward traffic and maintain operation.
Master Switch Election
The stack behaves as a single switching unit that is managed by a master switch elected by a
network manager or automatically from one of the member switches. The master switch
automatically creates and updates all the switching and optional routing tables. Any member of
the stack can become the master switch. Upon installation, or reboot of the entire stack, an
election process occurs among the switches in the stack. There is a hierarchy of selection criteria
for the election.
1. User priority—The network manager can select a switch to be master.
2. MAC address—Each switch reports its MAC address to all its neighbors for comparison. The
switch with the lowest MAC address is selected.
Master Switch Activities
The master switch acts as the primary point of contact for IP functions such as Telnet sessions,
pings, command-line interface (CLI), and routing information exchange. The master is
responsible for downloading forwarding tables to each of the subordinate switches. Multicast and
unicast routing tasks are implemented from the master. QoS and access control list (ACL)
configuration information is distributed from the master to the subordinates. When a new
subordinate switch is added, or an existing switch removed, the master will issue a notification of
this event and all the subordinate switches will update their tables accordingly.
Shared Network Topology Information
The master switch is responsible for collecting and maintaining correct routing and configuration
information. It keeps this information current by periodically sending copies or updates to all the
subordinate switches in the stack.