Users Guide

1118 MAC Addressing and Forwarding
Static addresses are configured by the administrator and added to the table.
Dynamic addresses are learned by examining information in the Ethernet
frame.
When a frame arrives on a port, the switch looks at the frame header to learn
the source MAC address of the frame, then adds the address, VLAN ID, and
the ingress port to the MAC address table. The address table is constantly
updated as new addresses are learned, and unused addresses age out.
A frame that has a destination MAC address that matches an entry in the
table is forwarded immediately to the associated port(s) within the same
VLAN.
What Information Is in the MAC Address Table?
Each entry in the address table, whether it is static or dynamic, includes the
MAC address, the VLAN ID associated with the MAC address, and the
interface on which the address was learned or configured.
Each port can maintain multiple MAC addresses, and a single MAC address
can be associated with multiple VLANs.
How Is the MAC Address Table Maintained Across a Stack?
The MAC address table is synchronized across all stack members. When a
member joins the stack, its previous MAC address table is overwritten by the
table maintained by the stack.
Default MAC Address Table Values
Table 29-1 summarizes the default values for the MAC address table.
Table 29-1. MAC Address Table Defaults
Parameter Default Value
Aging time 300 seconds
Dynamic addresses Enabled (automatically learned)
Static addresses None configured