Question 3
What are three components of the tag portion of an 802.1Q-tagged Ethernet frame? (Choose three.)
maximum transmission unit
canonical format indicator
Correct answer: ACD
Explanation:
The VLAN tag was invented to distinguish among different VLAN broadcast domains on a group of LAN switches. The VLAN tag is a two-byte field inserted between the source MAC address and the Ethertype (or length) field in an Ethernet frame. Another two-byte field, the Tag Protocol Identifier (TPI or TPID), precedes the VLAN tag field. The Canonical Format Indicator (CFI) bit indicates whether the following 12 bits of VLAN identifier conform to Ethernet or not. For Ethernet frames, this bit is always set to 0. (The other possible value, CFI=1, is used for Token Ring LANs, and tagged frames should never be bridged between an Ethernet and Token Ring LAN regardless of the VLAN tag or MAC address.) http://www.juniper.net/documentation/en_US/junos15.1/topics/concept/layer-2-networking-ethernet-frame-forwarding-802-1q-vlan-tag-mx-solutions.html
The VLAN tag was invented to distinguish among different VLAN broadcast domains on a group of LAN switches. The VLAN tag is a two-byte field inserted between the source MAC address and the Ethertype (or length) field in an Ethernet frame. Another two-byte field, the Tag Protocol Identifier (TPI or TPID), precedes the VLAN tag field.
The Canonical Format Indicator (CFI) bit indicates whether the following 12 bits of VLAN identifier conform to Ethernet or not. For Ethernet frames, this bit is always set to 0. (The other possible value, CFI=1, is used for Token Ring LANs, and tagged frames should never be bridged between an Ethernet and Token Ring LAN regardless of the VLAN tag or MAC address.)
http://www.juniper.net/documentation/en_US/junos15.1/topics/concept/layer-2-networking-ethernet-frame-forwarding-802-1q-vlan-tag-mx-solutions.html