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IEEE 802.1Q. 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.
A virtual local area network (VLAN) is any broadcast domain that is partitioned and isolated in a computer network at the data link layer (OSI layer 2). [2][3] In this context, virtual refers to a physical object recreated and altered by additional logic, within the local area network. Basically, a VLAN behaves like a virtual switch or network ...
Double tagging can only be exploited on switch ports configured to use native VLANs. [2]: 162 Trunk ports configured with a native VLAN don't apply a VLAN tag when sending these frames. This allows an attacker's fake VLAN tag to be read by the next switch. [4] Double tagging can be mitigated by any of the following actions (incl. IOS example):
IEEE 802.1ad is an amendment to the IEEE 802.1Q-1998 networking standard which adds support for provider bridges. It was incorporated into the base 802.1Q standard in 2011. [1] The technique specified by the standard is known informally as stacked VLANs or QinQ. The original 802.1Q specification allows a single virtual local area network (VLAN ...
A QinQ arrangement would add another four-octet tag containing a two-octet TPID using various EtherType values. 802.1Q VLAN tagging uses an 0x8100 EtherType value. The payload following includes a 16-bit tag control identifier (TCI) followed by an Ethernet frame beginning with a second (original) EtherType field for consumption by end stations.
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 ...
Private VLAN. Private VLAN, also known as port isolation, is a technique in computer networking where a VLAN contains switch ports that are restricted such that they can only communicate with a given uplink. The restricted ports are called private ports. Each private VLAN typically contains many private ports, and a single uplink.
VLAN Trunking Protocol (VTP) is a Cisco proprietary protocol that propagates the definition of Virtual Local Area Networks (VLAN) 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. VTP is available on most of the Cisco ...