13
MAC A
DDRESS
T
ABLE
M
ANAGEMENT
n
This chapter describes the management of static, dynamic, and blackhole MAC
address entries. For information about the management of multicast MAC address
entries, refer to “Multicast Overview” on page 185.
Introduction to the
MAC Address Table
An Ethernet switch is mainly used to forward packets at the data link layer, that is,
transmit the packets to the corresponding ports according to the destination MAC
address of the packets. To forward packets quickly, a switch maintains a MAC
address table, which is a Layer 2 address table recording the MAC
address-to-forwarding port association. Each entry in a MAC address table
contains the following fields:
■
Destination MAC address
■
ID of the VLAN which a port belongs to
■
Forwarding egress port numbers on the local switch
When forwarding a packet, an Ethernet switch adopts one of the two forwarding
methods based upon the MAC address table entries.
■
Unicast forwarding: If the destination MAC address carried in the packet is
included in a MAC address table entry, the switch forwards the packet through
the forwarding egress port in the entry.
■
Broadcast forwarding: If the destination MAC address carried in the packet is
not included in the MAC address table, the switch broadcasts the packet to all
ports except the one receiving the packet.
Introduction to MAC
Address Learning
MAC address table entries can be updated and maintained through the following
two ways:
■
Manual configuration
■
MAC address learning
Generally, the majority of MAC address entries are created and maintained
through MAC address learning. The following describes the MAC address learning
process of a switch:
1
As shown in Figure 41, User A and User B are both in VLAN 1. When User A
communicates with User B, the packet from User A needs to be transmitted to
Ethernet 1/0/1. At this time, the switch records the source MAC address of the
Summary of Contents for Switch 4210 9-Port
Page 22: ...20 CHAPTER 1 CLI CONFIGURATION ...
Page 74: ...72 CHAPTER 3 CONFIGURATION FILE MANAGEMENT ...
Page 84: ...82 CHAPTER 5 VLAN CONFIGURATION ...
Page 96: ...94 CHAPTER 8 IP PERFORMANCE CONFIGURATION ...
Page 108: ...106 CHAPTER 9 PORT BASIC CONFIGURATION ...
Page 122: ...120 CHAPTER 11 PORT ISOLATION CONFIGURATION ...
Page 140: ...138 CHAPTER 13 MAC ADDRESS TABLE MANAGEMENT ...
Page 234: ...232 CHAPTER 17 802 1X CONFIGURATION ...
Page 246: ...244 CHAPTER 20 AAA OVERVIEW ...
Page 270: ...268 CHAPTER 21 AAA CONFIGURATION ...
Page 292: ...290 CHAPTER 26 DHCP BOOTP CLIENT CONFIGURATION ...
Page 318: ...316 CHAPTER 29 MIRRORING CONFIGURATION ...
Page 340: ...338 CHAPTER 30 CLUSTER ...
Page 362: ...360 CHAPTER 33 SNMP CONFIGURATION ...
Page 368: ...366 CHAPTER 34 RMON CONFIGURATION ...
Page 450: ...448 CHAPTER 39 TFTP CONFIGURATION ...
Page 451: ......
Page 452: ...450 CHAPTER 39 TFTP CONFIGURATION ...
Page 470: ...468 CHAPTER 40 INFORMATION CENTER ...
Page 496: ...494 CHAPTER 44 DEVICE MANAGEMENT ...