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IEEE 802.1Q, often referred to as Dot1q, is the networking standard that supports virtual local area networking (VLANs) on an IEEE 802.3 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.
Insertion of the 802.1Q VLAN tag (four octets) into an Ethernet-II frame, with a typical VLAN arrangement of a tag protocol identifier (TPID) EtherType value of 0x8100. A QinQ arrangement would add another four-octet tag containing a two-octet TPID using various EtherType values.
Cisco also implemented VLANs over FDDI by carrying VLAN information in an IEEE 802.10 frame header, contrary to the purpose of the IEEE 802.10 standard. Both ISL and IEEE 802.1Q perform explicit tagging – the frame itself is tagged with VLAN identifiers. ISL uses an external tagging process that does not modify the Ethernet frame, while 802 ...
With ISL, an Ethernet frame is encapsulated with a header that transports VLAN IDs between switches and routers. With IEEE 802.1Q the tag is internal. This is a key advantage for IEEE 802.1Q as it means tagged frames can be sent over standard Ethernet links. ISL does add overhead to the frame as a 26-byte header containing a 10-bit VLAN ID.
Download QR code; Print/export Download as PDF; ... Superseded by 802.1Q-2003 802.1v-2001 VLAN Classification by Protocol and Port Incorporated into 802.1Q-2003
The IEEE 802.1Q tag or IEEE 802.1ad tag, if present, is a four-octet field that indicates virtual LAN (VLAN) membership and IEEE 802.1p priority. The first two octets of the tag are called the T ag P rotocol ID entifier (TPID) and double as the EtherType field indicating that the frame is either 802.1Q or 802.1ad tagged. 802.1Q uses a TPID of ...
In a tag stack scheme, switches can add, remove or modify single or multiple tags. It is easier for networking equipment makers to modify their existing equipment by creating multiple 802.1Q headers than to modify their equipment to implement some hypothetical new non-802.1Q extended VLAN ID field header.
VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that propagates the definition of Virtual Local Area Networks on the whole local area network. [1] To do this, VTP carries VLAN information to all the switches in a VTP domain. VTP advertisements can be sent over 802.1Q, and ISL trunks.