Chapter 17: MAC Address Table
344
Overview
The MAC address table stores the MAC addresses of all the network
devices that are connected to the switch’s ports. Each entry in the table
consists of a MAC address, a port number where an address was learned
by the switch, and an ID number of a VLAN where a port is a member.
The switch learns the MAC addresses of the network devices by
examining the source addresses in the packets as they arrive on the ports.
When the switch receives a packet that has a source address that is not in
the table, it adds the address, along with the port number where the
packet was received and the ID number of the VLAN where the port is a
member. The result is a table that contains the MAC addresses of all the
network devices that are connected to the switch’s ports.
The purpose of the table is to allow the switch to forward packets more
efficiently. When a packet arrives on a port, the switch examines the
destination address in the packet and refers to its MAC address table to
determine the port where the destination node of that address is
connected. It then forwards the packet to that port and on to the network
device.
If the switch receives a packet with a destination address that is not in the
MAC address table, it floods the packet to all its ports, excluding the port
where the packet was received. If the ports are grouped into virtual LANs,
the switch floods the packet only to those ports that belong to the same
VLAN from which the packet originated. This prevents packets from being
forwarded to inappropriate LAN segments and increases network security.
When the destination node responds, the switch adds the node’s MAC
address and port number to the MAC address table.
If the switch receives a packet with a destination address that is on the
same port on which the packet was received, it discards the packet
without forwarding it on to any port. Because both the source node and the
destination node for the packet are located on the same port on the
switch, there is no reason for the switch to forward the packet. This, too,
increases network performance by preventing frames from being
forwarded unnecessarily to other network devices.
MAC addresses learned by the switch are referred to as dynamic
addresses. Dynamic MAC addresses are not stored indefinitely in the
MAC address table. They are automatically deleted when they are
inactive. A MAC address is considered inactive if the switch does not
receive any frames from the network device after a specified period of
time. The switch assumes that the node with that MAC address is no
longer active and that its MAC address can be purged from the table. This
prevents the MAC address table from becoming filled with addresses of
nodes that are no longer active.
Содержание AT-9000/12PoE
Страница 4: ......
Страница 28: ...Contents 28...
Страница 36: ...Tables 36...
Страница 42: ...42...
Страница 76: ...Chapter 2 Starting a Management Session 76...
Страница 100: ...Chapter 4 Basic Command Line Management Commands 100...
Страница 112: ...112...
Страница 130: ...Chapter 7 Basic Switch Management 130...
Страница 170: ...Chapter 8 Basic Switch Management Commands 170...
Страница 284: ...Chapter 12 Power Over Ethernet Commands 284...
Страница 298: ...Chapter 13 IPv4 and IPv6 Management Addresses 298...
Страница 322: ...Chapter 14 IPv4 and IPv6 Management Address Commands 322...
Страница 342: ...Chapter 16 SNTP Client Commands 342...
Страница 371: ...AT 9000 Switch Command Line User s Guide 371 awplus write Save the configuration...
Страница 388: ...Chapter 19 Enhanced Stacking 388...
Страница 406: ...Chapter 20 Enhanced Stacking Commands 406...
Страница 414: ...Chapter 21 Port Mirror 414...
Страница 422: ...Chapter 22 Port Mirror Commands 422...
Страница 432: ...Chapter 23 Internet Group Management Protocol IGMP Snooping 432...
Страница 452: ...Chapter 25 Multicast Commands 452...
Страница 454: ...454...
Страница 462: ...Chapter 26 File System 462...
Страница 488: ...Chapter 29 Boot Configuration File Commands 488...
Страница 500: ...Chapter 30 File Transfer 500...
Страница 508: ...Chapter 31 File Transfer Commands 508...
Страница 510: ...510...
Страница 528: ...Chapter 33 Event Log Commands 528...
Страница 536: ...Chapter 34 Syslog Client 536...
Страница 544: ...544...
Страница 554: ...Chapter 36 Static Port Trunks 554...
Страница 562: ...Chapter 37 Static Port Trunk Commands 562...
Страница 574: ...Chapter 38 Link Aggregation Control Protocol LACP 574...
Страница 588: ...Chapter 39 LACP Commands 588...
Страница 590: ...590...
Страница 610: ...Chapter 40 STP RSTP and MSTP Protocols 610...
Страница 690: ...Chapter 45 Multiple Spanning Tree Protocol MSTP 690...
Страница 716: ...716...
Страница 740: ...Chapter 47 Port based and Tagged VLANs 740...
Страница 760: ...Chapter 48 Port based and Tagged VLAN Commands 760...
Страница 778: ...Chapter 49 GARP VLAN Registration Protocol 778...
Страница 800: ...Chapter 50 GARP VLAN Registration Protocol Commands 800...
Страница 816: ...Chapter 51 MAC Address based VLANs 816...
Страница 830: ...Chapter 52 MAC Address based VLAN Commands 830...
Страница 850: ...Chapter 55 Voice VLAN Commands 850...
Страница 860: ...Chapter 56 VLAN Stacking 860 Section III File System...
Страница 866: ...Chapter 57 VLAN Stacking Commands 866 Section III File System...
Страница 868: ...868...
Страница 878: ...Chapter 58 MAC Address based Port Security 878...
Страница 892: ...Chapter 59 MAC Address based Port Security Commands 892...
Страница 918: ...Chapter 60 802 1x Port based Network Access Control 918...
Страница 960: ...Chapter 61 802 1x Port based Network Access Control Commands 960...
Страница 962: ...962...
Страница 974: ...Chapter 62 SNMPv1 and SNMPv2c 974...
Страница 1024: ...1024...
Страница 1036: ...Chapter 65 sFlow Agent 1036...
Страница 1140: ...Chapter 68 LLDP and LLDP MED Commands 1140...
Страница 1146: ...Chapter 69 Address Resolution Protocol ARP 1146...
Страница 1154: ...Chapter 70 Address Resolution Protocol ARP Commands 1154...
Страница 1170: ...Chapter 71 RMON 1170 awplus show rmon alarm Use the SHOW RMON ALARM command to verify the new alarm...
Страница 1228: ...Chapter 73 Advanced Access Control Lists ACLs 1228...
Страница 1288: ...1288...
Страница 1300: ...Chapter 76 Local Manager Accounts 1300...
Страница 1310: ...Chapter 77 Local Manager Account Commands 1310...
Страница 1316: ...Chapter 78 Telnet Server 1316...
Страница 1324: ...Chapter 80 Telnet Client 1324...
Страница 1328: ...Chapter 81 Telnet Client Commands 1328...
Страница 1340: ...Chapter 82 Secure Shell SSH Server 1340...
Страница 1350: ...Chapter 83 SSH Server Commands 1350...
Страница 1362: ...Chapter 85 Non secure HTTP Web Browser Server Commands 1362...
Страница 1406: ...Chapter 88 RADIUS and TACACS Clients 1406...
Страница 1446: ...Chapter System Monitoring Commands 1446...
Страница 1476: ...Appendix B Management Software Default Settings 1476...