Week 4: VLAN's, VTP, & Port Configurations

Question 1

A VLAN is a single ________ domain

Answer 1

Broadcast

Question 2

At what OSI layer do switches provide VLAN connectivity?

Answer 2

Layer 2

Question 3

What is needed to pass data between two PCs that are connected to different VLANs?

Answer 3

A router or a Layer 3 switch

Question 4

Which Catalyst IOS switch command is used to assign a port to a VLAN?

Answer 4

“switchport access vlan “

Question 5

What is the Cisco proprietary method for trunk encapsulation?

Answer 5

ISL (Inter-Switch Link)

Question 6

What protocol dynamically negotiates trunking parameters?

Answer 6

Dynamic Trunk Protocol - DTP

can facilitate the automatic creation of trunks between two switches.

Question 7

How many different VLANs can an 802.1q trunk support?

Answer 7

4096

Question 8

Are the native VLAN frames tagged or untagged using ISL?

Answer 8

Tagged (Unlike 802.1Q tagging, there is no concept of a native VLAN in ISL because traffic from all VLANs is encapsulated with a full ISL header)

Question 9

If two switches each support all types of trunk encapsulation on a link between them, which one would be negotiated?

Answer 9

ISL (When two connected Cisco switches automatically negotiate a trunk with DTP they will choose ISL over 802.1Q unless one switch does not support it or specifically configured not to use ISL)

Question 10

Which VLANs are allowed on a trunk by default?

Answer 10

All active VLANs

Question 11

Which command configures a switch port to form a trunk without using negotiation?

Answer 11

“switchport mode trunk”

Question 12

Two hosts are connected to the same switch, but they can’t communicate with one another. You issue the “show vlan” command and notice that one of the two switch ports is not listed. What might be causing the connectivity issue?

Answer 12

1. Both switches are configured in the dynamic auto mode

Question 13

Define VLAN?

Answer 13

Virtual Local Area Network: used to segment a switch into more than one physical network or broadcast domain.
•They separate L2 Broadcast Domains.

Question 14

Define Broadcast Domain

Answer 14

A Broadcast Domain consists of all the devices that will receive any broadcast packet originating from any device within the network segment.

Question 15

Define ISL (Inter-Switch Link)

Answer 15

A Cisco proprietary VLAN tagging protocol. The ISL header is 26 bytes and it appends an additional CRC which is 4 bytes, for a total of 30 additional bytes to every ISL encapsulated frame.

Question 16

Define 802.1q

Answer 16

Is the network standard that supports VLANs on an Ethernet network. It is a system of tagging for Ethernet frames. • 802.1Q also adds a 4 byte tag into the Ethernet frame for VLAN tagging and is designed exclusively for point-to-point links.

Question 17

Define DTP

Answer 17

A Cisco proprietary, point-to-point, protocol that negotiates a common trunking mode between two switches.

Question 18

Define End-to-End VLAN

Answer 18

VLANs spread throughout the network on multiple switches. Follow the 80/20 rule where 80% traffic stays within the same VLAN while 20% is destined for a remote resource out of the workgroup VLAN.

Question 19

Define Local VLAN

Answer 19

VLANs are kept into the switch block and don’t go beyond the distribution layer. Follow the 20/80 rule where 20% traffic is local, and 80% of the traffic is destined to a remote resource across the core layer.

Question 20

Define a VLAN trunk

Answer 20

• Allow a switch to send traffic from many VLANs out through a single port
• is a physical path or link in a communications system that is designed to handle many transmissions simultaneously and that interconnects major switching centers or nodes.
• Trunks are used to interconnect switches to form networks, and to interconnect local area networks (LANs) to form wide area networks (WANs) or virtual LANs (VLANs).

Question 21

Common Terms

Answer 21

VLAN- Virtual Local Area Network, logical identifier for isolating a network

Trunk - A port enabled for VLAN tagging

Access - A port that does not tag and only accepts a single VLAN

Encapsulation - The process of modifying frames of data to include additional information

802.1Q - The most common encapsulation method for VLAN tagging. This is the method used by Meraki devices.

Native VLAN - The VLAN associated with all untagged traffic on a trunk