This link has been bookmarked by 21 people . It was first bookmarked on 17 Nov 2008, by Jimbox.
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09 Apr 16
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18 Mar 15
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09 Oct 14
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The standard defines a system of tagging for Ethernet frames and the accompanying procedures to be used by bridges and switches in handling such frames.
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dds a 32-bit field between the source MAC address and the EtherType/length fields of the original frame,
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02 Oct 14
theaceglVLAN Tagging
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IEEE 802.1Q
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system of tagging for Ethernet frames and the accompanying procedures to be used by bridges and switches in handling such frames.
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standard that supports virtual LANs (VLANs) on an Ethernet network
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When a frame enters the VLAN-aware portion of the network, a tag is added to represent the VLAN membership of the frame's port or the port/protocol combination, depending on whether port-based or port-and-protocol-based VLAN classification is being used
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native (or default) VLAN.
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Tag protocol identifier (TPID):
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n order to identify the frame as an IEEE 802.1Q-tagged frame.
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and maps to the frame priority level.
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Priority code point (PCP)
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1 (background), 0 (best effort), 2 (excellent effort), 3 (critical application), ..., 7 (network control).
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Drop eligible indicator (DEI):
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VLAN identifier (VID):
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allowing up to 4,094 VLANs.
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VLAN 1 (the default VLAN ID) is often reserved for a management VLAN
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28 Aug 14
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field set to a value of 0x8100 in order to identify the frame as an IEEE 802.1Q-tagged frame. This field is located at the same position as the EtherType/length field in untagged frames, and is thus used to distinguish the frame from untagged frames.
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18 Nov 13
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A trunk port can refer a port that sends and receives tagged frames on all VLANs, except the native VLAN, if one is configured. The term trunk may also be used to refer to a connection using link aggregation.
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Frames belonging to the native VLAN do NOT carry VLAN tags when sent over the trunk.
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20 Sep 13
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32-bit field between the source MAC address and the EtherType/Length fields of the original frame, leaving the minimum frame size unchanged at 64 bytes (octets) and extending the maximum frame size from 1,518 bytes to 1,522 bytes (For the payload a 42 octet minimum applies when 802.1Q is present, when absent, a 46 octet minimum applies. IEEE 802.3-2005 Clause 3.5). Two bytes are used for the tag protocol identifier (TPID), the other two bytes for tag control information (TCI). The TCI field is further divided into PCP, DEI, and VID.[1]
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24 May 13
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03 Sep 12
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- Tag Protocol Identifier (TPID): a 16-bit field set to a value of 0x8100 in order to identify the frame as an IEEE 802.1Q-tagged frame. This field is located at the same position as the EtherType/Length field in untagged frames, and is thus used to distinguish the frame from untagged frames.
16 bits 3 bits 1 bit 12 bits TPID TCI PCP CFI VID
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15 Jul 12
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16-bit field set to a value of 0x8100 in order to identify the frame as an IEEE 802.1Q-tagged frame
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Values are from 0 (best effort) to 7 (highest)
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hese values can be used to prioritize different classes of traffic (voice, video, data, etc.).
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12-bit field specifying the VLAN to which the frame belongs. The hexadecimal values of 0x000 and 0xFFF are reserved. All other values may be used as VLAN identifiers, allowing up to 4,094 VLANs
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A trunk port is a port that sends and receives tagged frames on all VLANs
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except the native VLAN
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Frames belonging to the native VLAN do NOT carry VLAN tags when sent over the trunk. Conversely, if an untagged frame is received on a trunk port, the frame is associated with the native VLAN configured on that port.
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frames on VLAN 2 that are sent from the aforementioned port are not given an 802.1Q header
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VLAN 2 being the native VLAN
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Frames that are received on that port and have no 802.1Q header are assigned to VLAN 2.
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all frames on those VLANs must carry tags to identify their VLAN membership
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19 Dec 11
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14 Oct 11
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IEEE 802.1Q is the networking standard that supports Virtual LANs (VLANs) on an Ethernet network. The standard defines a system of VLAN tagging for Ethernet frames and the accompanying procedures to be used by bridges and switches in handling such frames. The standard also provides provisions for a quality of service prioritization scheme commonly known as IEEE 802.1p and defines the Generic Attribute Registration Protocol
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A company wishes to provide data separation and security between network traffic from its various departments by creating separate logical networks for each of its departments dispersed throughout the enterprise, while using only one corporate physical network. A network administrator assigns a unique VLAN to each department. Edge switches on the corporate network are configured to insert an appropriate VLAN tag into all data frames arriving from equipment belonging to a given department. After the frames are transmitted on their respective VLANs through the corporate network, the VLAN tag is stripped before the frame is sent to another computer belonging to the same department.
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17 Nov 08
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- Tag Protocol Identifier (TPID): a 16-bit field set to a value of 0x8100 in order to identify the frame as an IEEE 802.1Q-tagged frame.
- Priority Code Point (PCP): a 3-bit field which refers to the IEEE 802.1p priority. It indicates the frame priority level from 0 (lowest) to 7 (highest), which can be used to prioritize different classes of traffic (voice, video, data, etc).
- Canonical Format Indicator (CFI): a 1-bit field. If the value of this field is 1, the MAC address is in non-canonical format. If the value is 0, the MAC address is in canonical format. It is always set to zero for Ethernet switches. CFI is used for compatibility between Ethernet and Token Ring networks. If a frame received at an Ethernet port has a CFI set to 1, then that frame should not be bridged to an untagged port.
- VLAN Identifier (VID): a 12-bit field specifying the VLAN to which the frame belongs. A value of 0 means that the frame doesn't belong to any VLAN; in this case the 802.1Q tag specifies only a priority and is referred to as a priority tag. A value of hex FFF is reserved for implementation use. All other values may be used as VLAN identifiers, allowing up to 4094 VLANs. On bridges, VLAN 1 is often reserved for management.
802.1Q does not actually encapsulate the original frame. Instead, for Ethernet II frames, it adds a 32-bit field between the source MAC address and the EtherType/Length fields of the original frame. Since the FCS becomes invalid, it is regenerated. That field has the following format:
16 bits 3 bits 1 bit 12 bits TPID PCP CFI VID -
Double-tagging(QinQ) can be useful for Internet Service Providers, allowing them to use VLANs internally while mixing traffic from clients that are already VLAN-tagged. The outer tag comes first, followed by the inner tag. In such cases, an alternate TPID such as hex 9100, or even 9200 or 9300, sometimes may be used for the outer tag; however this is being deprecated by 802.1ad, which specifies 88a8 for service-provider outer tags.
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