Virtual Lan Read And Learn

Front 1

A LAN includes all devices in the same broadcast domain.

Back 1

a broadcast sent by one host in a VLAN will be received and processed by all the other hosts

Front 2

Without VLANs, a switch considers all its interfaces to be in the same broadcast domain

Back 2

These are just a few reasons for
separating hosts into different VLANs.

Tocreate more flexible designs that group users by department, or by groups that work
together, instead of by physical location
■ Tosegment devices into smaller LANs (broadcast domains) to reduce overhead caused
to each host in the VLAN
■ To reduce the workload for the Spanning Tree Protocol (STP) by limiting a VLAN to
a single access switch
■ Toenforce better security by keeping hosts that work with sensitive data on a separate
VLAN
■ Toseparate traffic sent by an IP phone from traffic sent by PCs connected to the phones

Front 3

VLAN tagging, by which the sending switch adds
another header to the frame before sending it over the trunk. This extra VLAN header
includes a VLAN identifier (VLAN ID) field so that the sending switch can list the VLAN
ID and the receiving switch can then know in what VLAN each frame belongs.

Back 3

Cisco switches support two different trunking protocols: Inter-Switch Link (ISL) and IEEE
802.1Q

Front 4

Cisco created ISL many years before the IEEE created the 802.1Q

ISL is Cisco proprietary

Back 4

ISL fully encapsulates each original Ethernet
frame in an ISL header and trailer. The original Ethernet frame inside the ISL header and
trailer remains unchanged.

Front 5

Also, the source and destination addresses
in the ISL header use MAC addresses of the sending and receiving switch, as opposed to
the devices that actually sent the original frame

Back 5

802.1Q inserts an extra 4-byte VLAN header into the original frame’s
Ethernet header

Front 6

unlike ISL, the frame still has the same original source and
destination MAC addresses

Back 6

because the original header has been expanded, 802.1Q
encapsulation forces a recalculation of the original frame check sequence (FCS) field

Front 7

Both trunking protocols support the same number of VLANs, specifically 4094 VLANs.
Both protocols use 12 bits of the VLAN header to number VLANs, supporting 212, or 4096,
VLAN IDs, minus two reserved values (0 and 4095).

Back 7

ISL and 802.1Q both support a separate instance of Spanning Tree Protocol (STP) for each
VLAN

Front 8

802.1Q Header

Back 8

DestAdd|SourAdd|Tag(new)|Len.Type|Data|FCS

Tag = Type(16b)|Pri(3b)|Flag(1b)|VlanID(12B)

Front 9

comparisons between 802.1Q and VSL:

Inserts another 4-byte header instead of completely encapsulating the original frame

Back 9

ISL: NO
802.1Q: Yes

Front 10

comparisons between 802.1Q and VSL:

Supports normal range (1-1005) and extended range (1006-4094) VLANS

Back 10

ISL: Yes
802.1Q: Yes

Front 11

comparisons between 802.1Q and VSL:

Allows multiple spanning trees

Back 11

ISL: Yes
802.1Q: Yes

Front 12

comparisons between 802.1Q and ISL:
Uses a native VLAN:

Back 12

ISL: No
802.1Q: Yes

Front 13

VTP Synchronization
(configuration revision numbers and the VTP update process)

Back 13

1. Configures a new VLAN from a CLI of a VTP server
2. VTP server updates its VLAN db revision number +1
3. The server sends VTP update messages out its trunk interfaces stating new revision number
4. The VTP client switches notice that the update list a higher revision number
5. The two client switches update there VLAN db based on the servers VTP updates.

Front 14

3 requirements for VTP to work between 2 switches

Back 14

1. The link between the switches must be operating as a VLAN trunk.
2. The two switches case sensitive VTP domain name must match.
3. If configured on at least one of the switches the two swithces case sensitive VTP passwords must math.

Front 15

VTP features summery:
Only sends VTP messages out ISL or 802.1Q trunks

Back 15

Server: Yes
Client: Yes
Transparent: Yes

Front 16

VTP features summery:
Supports CLI configuration of VLANS

Back 16

Server: Yes
Client: No
Transparent: Yes

Front 17

VTP features summery:
Can use normal range VLANS (1-1005)

Back 17

Server: Yes
Client: Yes
Transparent: Yes

Front 18

VTP features summery:
Can use extended range Vlans (1006-4095)

Back 18

Server: No
Client: No
Transparent: Yes

Front 19

VTP features summery:
Synchronizes its own config database when recieving VTP messages with a higher revision number

Back 19

Server: Yes
Client: Yes
Transparent: Yes

Front 20

VTP features summery:
Creates and sends preiodic VTP updates every 5 minutes

Back 20

Server: Yes
Client: Yes
Transparent: No

Front 21

VTP features summery:
Does not process recieved VTP updates, but does forward recieved VTP updates out other trunks

Back 21

Server: No
Client: No
Transparent: Yes

Front 22

VTP features summery:
Places the VLAN ID, VLAN name and VTP configuration into the Running-config file

Back 22

Server: No
Client: No
Transparent: Yes

Front 23

VTP features summery:
Places the VLAN ID, VLAN name and VTP configuration into the vlan.dat file in flash

Back 23

Server: Yes
Client: Yes
Transparent: Yes

Front 24

Default VTP and VLAN config

Back 24

1. VTP server mode
2. No VTP domain name
3. VLAN1, VLans 1002-1005 are automatically configured (cannot be deleted)
4. All access interfaces are assigned to VLAN1

Front 25

Options of the Switchport Mode command

Back 25

Access, trunk, dynamic desirable, dynamic auto

Front 26

Expected trunking operational mode based on configured administrative modes.

Access:

Back 26

Access: Access
Dynamic Auto: Access
Trunk: Access
Dynamic Desireable: Access

Front 27

Expected trunking operational mode based on configured administrative modes.

Dynamic Auto:

Back 27

Access: Access
Dynamic Auto: Access
Trunk: Trunk
Dynamic Desirable: Trunk

Front 28

Expected trunking operational mode based on configured administrative modes.

Trunk:

Back 28

Access: Access
Dynamic Auto: Trunk
Trunk: Trunk
Dynamic Desireable: Trunk

Front 29

Expected trunking operational mode based on configured administrative modes.

Dynamic Desireable

Back 29

Access: Access
Dynamic Auto: Trunk
Trunk: Trunk
Dynamic Desireable: Trunk

Front 30

4 reasons why a trunk doesn't pass traffic for a vlan:

Back 30

1. A VLAN has been removed from the trunks allowed VLAN list
2. A VlAN does not exist, or is not active, in the switches VLAN database.
3. A VLAN has been automaticaly pruned by VTP
4. A VLAN's STP instance has placed the trunk interface into a state other than a forwarding state.

Front 31

Recomendations on how to protect unused switch ports

Back 31

1. Administratively disable the unused interface, using the shutdown interface subcommand
2. Prevent trunking from being negotiated when the port is enabled by using the switchport nonegotiate interface subcommand to disable negotiation, or the switchport mode access interface subcommand to statically configure the interface as an access interface.
3. Assign the port to an unused VLAN, sometimes called a parking lot VLAN using the switchport access vlan number interface subcommand.

Front 32

Vlan configuration checklist:
Step1:

Back 32

Configure the VTP mode using the vtp mode {server|client} global configuration command

Front 33

Vlan configuration checklist
Step 2:

Back 33

Configure the VTP (case-sensitive) domain name using the vtp domain domain-name global configuration command

Front 34

Vlan configuration checklist
Step 3.

Back 34

(optional) On both clients and servers, configure the same case-sensitive password using the vtp password password-value global configuration command

Front 35

Vlan configuration checklist
Step 4

Back 35

(optional) Configure VTP pruning on the VTP servers using the vtp pruning global configuration command

Front 36

Vlan configuration checklist
Step 5

Back 36

(optional) Enable VTP version 2 global configuration command

Front 37

VTP configuration checklist
Step 6:

Back 37

Bring up trunks between switches

Front 38

Configuration command:
vtp domain

Back 38

Stored: vlan.dat
view: show vtp status

Front 39

configuration command:
vtp mode

Back 39

stored: vlan.dat
view: show vtp status

Front 40

configuration command:
vtp password

Back 40

stored: vlan.dat
view: show vtp password

Front 41

configuration command:
vtp pruning

Back 41

stored: vlan.dat
view: show vtp status

Front 42

configuration command:
vlan vlan-id

Back 42

stored: vlan.dat
view: show vlan [brief]

Front 43

configuration command:
name vlan-name

Back 43

stored: vlan.dat
view: show vlan[brief]

Front 44

configuration command:
switchport access vlan vlan-id

Back 44

stored: running-config
view: show running-config, show interfaces switchport

Front 45

configuration command:
switchport voice vlan vlan-id

Back 45

stored: running-config
view: show running-config, show interfaces switchport