Which of the following statements is TRUE about trunk ports?
A.
A trunk port connects an end-user workstation to a switch.
B.
A trunk port uses 802.1q to identify traffic from different VLANs.
C.
A trunk port supports a single VLAN.
D.
A trunk port uses a straight-through Ethernet cable when connecting two switches.
Explanation:
A switch port can operate as an access port or a trunk port. An access port is used to connect to an end-user device, such as a workstation, server, or printer,while
a trunk port is used to connect to neighboring switches or routers. The trunk link is responsible for carrying data between workstations connected to different
switches, or a switch and a router configured for inter-VLAN routing. For example, in the diagram below where VLANs are in use on both switches and inter-VLAN
routing is configured, the interfaces will operate as follows:
– SW1 – Fa0/1 and Fa0/2 are trunk links, Fa0/0 is an access link
– SW2 – Fa0/0 is trunk link and Fa0/1 is an access link
-RTR – Fa0/2 is a trunk link
With the exception of frames traveling on the native VLAN, data frames crossing a trunk link must be frame tagged over the link to identify the VLAN that sourced
the frame. The receiving switch sees the VLAN ID, and uses this information to forward the frame appropriately. 802.1q and ISL are the two possible frame tagging
methods between Cisco switches. In summary, some facts about access and trunk ports:
Access ports:
– Carry traffic for a single VLAN
– Connect end user workstations to the switch
– Use a straight-through cable to connect to the device
Trunk ports:
– Facilitate inter-VLAN communication when connected to a Layer 3 device
– Carry traffic from multiple VLANs
– Use 802.1q to identify traffic from different VLANs
When a new trunk link is created on a switch, all VLANs are allowed to use the trunk, by default.
Trunk ports are used between switches and routers, and do not connect to end-user workstations.
Trunk ports support all VLANs known to the switch by default, so that devices in the same VLAN can communicate across multiple switches. Trunk ports are not
limited to a single VLAN, as access ports are.Trunk ports connected between switches using crossover Ethernet cables, not straight-through Ethernet cables. Trunk ports between switches and routers use
straight-through cables.
Objective:
LAN Switching Fundamentals
Sub-Objective:
Configure, verify, and troubleshoot interswitch connectivityhttp://www.ciscopress.com/articles/article.asp?p=29803&seqNum=3
