Port-Based VLAN
89
In Figure 26 DA refers to the destination MAC address, SA refers to the source
MAC address, and Type refers to the protocol type of the packet. IEEE 802.1Q
protocol defines that a 4-byte VLAN tag is encapsulated after the destination MAC
address and source MAC address to show the information about VLAN.
Figure 27
Format of VLAN tag
As shown in Figure 27, a VLAN tag contains four fields, including TPID, priority,
CFI, and VLAN ID.
■
TPID is a 16-bit field, indicating that this data frame is VLAN-tagged. By
default, it is 0x8100 in 3Com series Ethernet switches.
■
Priority is a 3-bit field, referring to 802.1p priority. Refer to “QoS
Configuration” on page 657 for details.
■
CFI is a 1-bit field, indicating whether the MAC address is encapsulated in the
standard format in different transmission media. This field is not described in
detail in this chapter.
■
VLAN ID is a 12-bit field, indicating the ID of the VLAN to which this packet
belongs. It is in the range of 0 to 4,095. Generally, 0 and 4,095 is not used, so
the field is in the range of 1 to 4,094.
VLAN ID identifies the VLAN to which a packet belongs. When the switch receives
an un-VLAN-tagged packet, it will encapsulate a VLAN tag with the default VLAN
ID of the inbound port for the packet, and the packet will be assigned to the
default VLAN of the inbound port for transmission.
Port-Based VLAN
Port-based VLAN technology introduces the simplest way to classify VLANs. You
can isolate the hosts and divide them into different virtual workgroups through
assigning the ports on the device connecting to hosts to different VLANs.
This way is easy to implement and manage and it is applicable to hosts with
relatively fixed positions.
Link Types of Ethernet
Ports
An Ethernet port on a Switch 7750 can be of the following three link types.
■
Access. An access port can belong to only one VLAN. It is used to provide
network access for terminal users.
■
Trunk: A trunk port can belong to more than one VLAN. It can receive/send
packets from/to multiple VLANs, and is generally used to connect another
switch.
■
Hybrid: A hybrid port can belong to more than one VLAN. It can receive/send
packets from/to multiple VLANs, and can be used to connect either a switch or
a user PC.
n
A hybrid port allows the packets of multiple VLANs to be sent without tags, but a
trunk port only allows the packets of the default VLAN to be sent without tags.
TPID
DA&SA
Type
Priority
CFI
VLAN ID
VLAN Tag
Summary of Contents for Switch 7754
Page 32: ...32 CHAPTER 1 CLI OVERVIEW ...
Page 70: ...70 CHAPTER 5 LOGGING IN USING MODEM ...
Page 76: ...76 CHAPTER 7 LOGGING IN THROUGH NMS ...
Page 86: ...86 CHAPTER 9 CONFIGURATION FILE MANAGEMENT ...
Page 120: ...120 CHAPTER 13 ISOLATE USER VLAN CONFIGURATION ...
Page 126: ...126 CHAPTER 14 SUPER VLAN ...
Page 136: ...136 CHAPTER 16 IP PERFORMANCE CONFIGURATION ...
Page 152: ...152 CHAPTER 17 IPX CONFIGURATION ...
Page 164: ...164 CHAPTER 19 QINQ CONFIGURATION ...
Page 172: ...172 CHAPTER 21 SHARED VLAN CONFIGURATION ...
Page 182: ...182 CHAPTER 22 PORT BASIC CONFIGURATION ...
Page 198: ...198 CHAPTER 24 PORT ISOLATION CONFIGURATION ...
Page 208: ...208 CHAPTER 25 PORT SECURITY CONFIGURATION ...
Page 224: ...224 CHAPTER 27 DLDP CONFIGURATION ...
Page 232: ...232 CHAPTER 28 MAC ADDRESS TABLE MANAGEMENT ...
Page 240: ...240 CHAPTER 29 CENTRALIZED MAC ADDRESS AUTHENTICATION CONFIGURATION ...
Page 280: ...280 CHAPTER 30 MSTP CONFIGURATION ...
Page 348: ...348 CHAPTER 35 IS IS CONFIGURATION ...
Page 408: ...408 CHAPTER 39 802 1X CONFIGURATION ...
Page 412: ...412 CHAPTER 40 HABP CONFIGURATION ...
Page 422: ...422 CHAPTER 41 MULTICAST OVERVIEW ...
Page 426: ...426 CHAPTER 42 GMRP CONFIGURATION ...
Page 480: ...480 CHAPTER 47 PIM CONFIGURATION ...
Page 506: ...506 CHAPTER 48 MSDP CONFIGURATION ...
Page 552: ...552 CHAPTER 51 TRAFFIC ACCOUNTING CONFIGURATION ...
Page 570: ...570 CHAPTER 53 HA CONFIGURATION ...
Page 582: ...582 CHAPTER 54 ARP CONFIGURATION SwitchA arp protective down recover interval 200 ...
Page 622: ...622 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Page 684: ...684 CHAPTER 61 QOS CONFIGURATION ...
Page 718: ...718 CHAPTER 63 CLUSTER ...
Page 738: ...738 CHAPTER 67 UDP HELPER CONFIGURATION ...
Page 752: ...752 CHAPTER 69 RMON CONFIGURATION ...
Page 772: ...772 CHAPTER 70 NTP CONFIGURATION ...
Page 796: ...796 CHAPTER 72 FILE SYSTEM MANAGEMENT ...
Page 802: ...802 CHAPTER 73 BIMS CONFIGURATION ...
Page 814: ...814 CHAPTER 74 FTP AND TFTP CONFIGURATION ...
Page 830: ...830 CHAPTER 75 INFORMATION CENTER ...
Page 836: ...836 CHAPTER 76 DNS CONFIGURATION ...
Page 852: ...852 CHAPTER 77 BOOTROM AND HOST SOFTWARE LOADING ...
Page 858: ...858 CHAPTER 78 BASIC SYSTEM CONFIGURATION DEBUGGING ...