Introduction to VLAN
85
IEEE802.1Q defines a four-byte VLAN Tag between the DA&SA field and the Type
field to carry VLAN-related information, as shown in Figure 27.
Figure 27
The position and the format of the VLAN Tag
The VLAN Tag comprises four fields: the tag protocol identifier (TPID) field, the
Priority field, the canonical format indicator (CFI) field, and the VLAN ID field.
■
The TPID field, 16 bits in length and with a value of 0x8100, indicates that a
packet carries a VLAN tag with it.
■
The Priority field, three bits in length, indicates the 802.1p priority of a packet.
For information about packet priority, refer to “Introduction to QoS Policies”
on page 870.
■
The CFI field, one bit in length, specifies whether or not the MAC addresses are
encapsulated in standard format when packets are transmitted across different
medium. With the field set to 0, MAC addresses are encapsulated in standard
format; with the field set to 1, MAC addresses are encapsulated in
non-standard format. The filed is 0 by default.
■
The VLAN ID field, 12 bits in length and with its value ranging from 0 to 4095,
identifies the ID of the VLAN a packet belongs to. As VLAN IDs of 0 and 4095
are reserved by the protocol, the value of this field actually ranges from 1 to
4094.
A network device determines the VLAN to which a packet belongs to by the VLAN
ID field the packet carries. The VLAN Tag determines the way a packet is
processed. For more information, refer to section “Introduction to Port-Based
VLAN” on page 87.
n
The frame format mentioned here is that of Ethernet II. Besides Ethernet II
encapsulation, other types of encapsulation, including 802.2 LLC, 802.2 SNAP,
and 802.3 raw are also supported by Ethernet. The VLAN tag fields are also added
to packets adopting these encapsulation formats for VLAN identification.
VLAN Classification
Based on how VLANs are established, VLANs fall into different categories. The
following types are the most commonly used:
■
Port-based
■
MAC address-based
■
Protocol-based
■
IP-subnet-based
■
Policy-based
■
Other types
The the Switch 4800G support port-based VLAN, MAC address-based VLAN,
protocol-based VLAN, and IP-subnet-based VLAN.
TPID
DA&SA
Type
Priority CFI
VLAN ID
VLAN Tag
Содержание 4800G Series
Страница 26: ...26 CHAPTER NETWORKING APPLICATIONS ...
Страница 30: ...30 CHAPTER 1 LOGGING IN TO AN ETHERNET SWITCH ...
Страница 62: ...62 CHAPTER 3 LOGGING IN THROUGH TELNET ...
Страница 70: ...70 CHAPTER 5 LOGGING IN THROUGH WEB BASED NETWORK MANAGEMENT SYSTEM ...
Страница 72: ...72 CHAPTER 6 LOGGING IN THROUGH NMS ...
Страница 82: ...82 CHAPTER 8 CONTROLLING LOGIN USERS ...
Страница 98: ...98 CHAPTER 9 VLAN CONFIGURATION ...
Страница 108: ...108 CHAPTER 10 VOICE VLAN CONFIGURATION ...
Страница 119: ...GVRP Configuration Examples 119 DeviceB display vlan dynamic No dynamic vlans exist ...
Страница 120: ...120 CHAPTER 11 GVRP CONFIGURATION ...
Страница 160: ...160 CHAPTER 17 PORT ISOLATION CONFIGURATION ...
Страница 172: ...172 CHAPTER 19 LINK AGGREGATION CONFIGURATION ...
Страница 196: ...196 CHAPTER 22 DLDP CONFIGURATION ...
Страница 240: ...240 CHAPTER 23 MSTP CONFIGURATION ...
Страница 272: ...272 CHAPTER 27 RIP CONFIGURATION ...
Страница 364: ...364 CHAPTER 29 IS IS CONFIGURATION ...
Страница 426: ...426 CHAPTER 31 ROUTING POLICY CONFIGURATION ...
Страница 442: ...442 CHAPTER 33 IPV6 RIPNG CONFIGURATION ...
Страница 466: ...466 CHAPTER 35 IPV6 IS IS CONFIGURATION ...
Страница 488: ...488 CHAPTER 36 IPV6 BGP CONFIGURATION ...
Страница 498: ...498 CHAPTER 37 ROUTING POLICY CONFIGURATION ...
Страница 540: ...540 CHAPTER 40 TUNNELING CONFIGURATION ...
Страница 552: ...552 CHAPTER 41 MULTICAST OVERVIEW ...
Страница 604: ...604 CHAPTER 43 MLD SNOOPING CONFIGURATION ...
Страница 628: ...628 CHAPTER 46 IGMP CONFIGURATION ...
Страница 699: ...Troubleshooting MSDP 699 4 Verify that the C BSR address is different from the anycast RP address ...
Страница 700: ...700 CHAPTER 48 MSDP CONFIGURATION ...
Страница 812: ...812 CHAPTER 57 DHCP SERVER CONFIGURATION ...
Страница 822: ...822 CHAPTER 58 DHCP RELAY AGENT CONFIGURATION ...
Страница 834: ...834 CHAPTER 61 BOOTP CLIENT CONFIGURATION ...
Страница 850: ...850 CHAPTER 63 IPV4 ACL CONFIGURATION ...
Страница 856: ...856 CHAPTER 64 IPV6 ACL CONFIGURATION ...
Страница 860: ...860 CHAPTER 65 QOS OVERVIEW ...
Страница 868: ...868 CHAPTER 66 TRAFFIC CLASSIFICATION TP AND LR CONFIGURATION ...
Страница 888: ...888 CHAPTER 69 PRIORITY MAPPING ...
Страница 894: ...894 CHAPTER 71 TRAFFIC MIRRORING CONFIGURATION ...
Страница 904: ...904 CHAPTER 72 PORT MIRRORING CONFIGURATION ...
Страница 930: ...930 CHAPTER 74 UDP HELPER CONFIGURATION ...
Страница 990: ...990 CHAPTER 79 FILE SYSTEM MANAGEMENT CONFIGURATION ...
Страница 1000: ...1000 CHAPTER 80 FTP CONFIGURATION ...
Страница 1020: ...1020 CHAPTER 82 INFORMATION CENTER CONFIGURATION ...
Страница 1038: ...1038 CHAPTER 84 SYSTEM MAINTAINING AND DEBUGGING ...
Страница 1046: ...1046 CHAPTER 85 DEVICE MANAGEMENT ...
Страница 1129: ...SSH Client Configuration Examples 1129 SwitchB ...
Страница 1130: ...1130 CHAPTER 88 SSH CONFIGURATION ...
Страница 1160: ...1160 CHAPTER 90 RRPP CONFIGURATION ...
Страница 1180: ...1180 CHAPTER 91 PORT SECURITY CONFIGURATION ...
Страница 1192: ...1192 CHAPTER 92 LLDP CONFIGURATION ...
Страница 1202: ...1202 CHAPTER 93 POE CONFIGURATION ...
Страница 1218: ...1218 CHAPTER 96 HTTPS CONFIGURATION ...