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Implementing Ethernet Virtual LANs


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VLANs
With __, a switch can configure some interfaces into one broadcast domain and some into another, creating multiple broadcast domains.
CPU overhead
To reduce __ on each device by reducing the number of devices that receive each broadcast frame.
security risks
To reduce __ by reducing the number of hosts that receive copies of frames that the switches flood (broadcasts, multicasts, and unknown unicasts)
security for hosts
To improve __ that send sensitive data by keeping those hosts on a separate VLAN.
flexible designs
To create more __ that group users by department, or by groups that work together, instead of by physical location.
workload
To reduce the __ for the Spanning Tree Protocol (STP) by limiting a VLAN to a single access switch.
VLAN trunking
When using VLANs in networks that have multiple interconnected switches, the switches need to use __ on the links between the switches.
VLAN tagging
VLAN trunking causes the switches to use a process called __, by which the sending switch adds another header to the frame before sending it over the trunk.
VLAN identifier
This extra trunking header includes a __ field so that the sending switch can associate the frame with a particular VLAN ID, and the receiving switch can then know in what VLAN each frame belongs.
one link
VLAN trunking creates __ between switches that supports as many VLANs as you need.
all the VLANs
As a VLAN trunk, the switches treat the link as if it were a part of __.
separate, VLAN number
At the same time, the trunk keeps the VLAN traffic __, so frames in VLAN 10 would not go to devices in VLAN 20, and vice versa, because each frame is identified by __ as it crosses the trunk.
small header
The use of trunking allows switches to pass frames from multiple VLANs over a single physical connection by adding a __ to the Ethernet frame.
10
SW2 will flood the frame only into VLAN 10, and not into VLAN 20. So, before sending the frame, SW1 adds a VLAN header to the original Ethernet frame, with the VLAN header listing a VLAN ID of __.
VLAN header
When SW2 receives the frame, it understands that the frame is in VLAN 10. SW2 then removes the __, forwarding the original frame out its interfaces in VLAN 10.
Inter-Switch Link, IEEE 802.1Q
Cisco has supported two different trunking protocols over the years: __ and __.
ISL, 802.1Q
Cisco created the __ long before __, in part because the IEEE had not yet defined a VLAN trunking standard.
802.1Q, ISL
Today, __ has become the more popular trunking protocol, with Cisco not even supporting __ in some of its newer models of LAN switches, including the 2960 switches.
tag
While both ISL and 802.1Q __ each frame with the VLAN ID, the details differ.
4-byte
802.1Q inserts an extra __ 802.1Q VLAN header into the original frame’s Ethernet header.
12-bit VLAN ID
As for the fields in the 802.1Q header, only the __ field inside the 802.1Q header matters for topics discussed in this course.
4094
The VLAN ID field supports a theoretical maximum of 212 (4096) VLANs, while in practice, it supports a maximum of 4094.
0, 4095
Both 802.1Q and ISL use 12 bits to tag the VLAN ID, with two reserved values [__ and __].
normal range, extended range
Cisco switches break the range of VLAN IDs (1–4094) into two ranges: the __ and the __.
1, 1005
All switches can use normal-range VLANs with values from __ to __.
1005, 4094
Only some switches can use extended-range VLANs with VLAN IDs from __ to __.
VLAN Trunking Protocol
The rules for which switches can use extended-range VLANs depend on the configuration of the __.
native VLAN
802.1Q also defines one special VLAN ID on each trunk as the __ (defaulting to use VLAN 1).
native VLAN
802.1Q simply does not add an 802.1Q header to frames in the __.
802.1Q header
When the switch on the other side of the trunk receives a frame that does not have an __, the receiving switch knows that the frame is part of the native VLAN.
one VLAN
The native VLAN concept gives switches the capability of at least passing traffic in __, which can allow some basic functions, like reachability to telnet into a switch.
same subnet
When including VLANs in a campus LAN design, the devices in a VLAN need to be in the __.
route Layer 3 packets
Instead of switching Layer 2 Ethernet frames between the two VLANs, the network must __ between the two subnets.
VLAN trunk
A much less expensive option uses a __ between the switch and router, requiring only one physical link between the router and switch, while supporting all VLANs.
router-on-a-stick
Because the router has a single physical link connected to the LAN switch, this design is sometimes called a __.
performance
Routing packets using a physical router, even with the VLAN trunk in the router-on-a-stick model, still has one significant problem: __.
Layer 3 switches
Vendors long ago started combining the hardware and software features of their Layer 2 LAN switches, plus their Layer 3 routers, creating products called __.
subnets, VLANs
Today, many medium- to large-sized enterprise campus LANs use Layer 3 switches to route packets between __ (__) in a campus.
Layer 2 LAN switch, Layer 3 router
A Layer 3 switch works a lot like the original two devices on which the Layer 3 switch is based: a __ and a __.
vlan {vlan-id}
[1-A] From configuration mode, use the __ global configuration command to create the VLAN and to move the user into VLAN configuration mode.
name {name}
[1-B] (Optional) Use the __ VLAN subcommand to list a name for the VLAN.
4-digit decimal VLAN ID
If not configured, the VLAN name is VLANZZZZ, where ZZZZ is the __.
interface
[2-A] Use the __ command to move into interface configuration mode for each desired interface.
switchport access vlan {id-number}
[2-B] Use the __ interface subcommand to specify the VLAN number associated with that interface.
switchport mode access
[2-C] (Optional) To disable trunking on that same interface, so that the interface does not negotiate to become a trunk, use the __ interface subcommand.
vlan 11, vlan 12, vlan 13, switchport access vlan 11, 12 , 13
If you want to put the switch’s ports in three VLANs—11, 12, and 13—you just add three vlan commands: __, __ and __. Then, for each interface, add a __ (or __ or __) command to assign that interface to the proper VLAN.
five nondeletable VLANs
The example begins with the show vlan brief command, confirming the default settings of __, with all interfaces assigned to VLAN 1.
1002, 1005
VLAN 1 cannot be deleted, but can be used. VLANs __ - __ cannot be deleted and cannot be used as access VLANs today.
VLAN Trunking Protocol
__ is a Cisco-proprietary tool on Cisco switches that advertises each VLAN configured in one switch (with the vlan number command) so that all the other switches in the campus learn about that VLAN.
server, client, transparent
Each switch can use one of three VTP modes: __, __, or __.
server, client
Switches use either VTP __ or __ mode when the switch wants to use VTP for its intended purpose of dynamically advertising VLAN configuration information.
VTP transparent mode
With many Cisco switches and IOS versions, VTP cannot be completely disabled on a Cisco switch; instead, the switch disables VTP by using __.
show vtp status
If you happen to do lab exercises with real switches or with simulators, and you see unusual results with VLANs, check the VTP status with the __ command.
server
The __ switches can configure VLANs in the standard range only (1–1005).
client
The __ switches cannot configure VLANs.
transparent, ignore
If possible, switch to VTP __ mode and __ VTP for your switch configuration practice for the CCENT and CCNA exam.
statically
Trunking configuration between two Cisco switches can be very simple if you just __ configure trunking.
802.1Q
If two Cisco 2960 switches connect to each other, they support only __ for VLAN trunking.
switchport mode trunk
You could literally add one interface subcommand for the switch interface on each side of the link (__), and you would create a VLAN trunk that supported all the VLANs known to each switch.
switchport trunk encapsulation {dot1q | isl | negotiate}
Switches that support both types of trunking use the __ interface subcommand to either configure the type or allow DTP to negotiate the type.
administrative mode, operational mode
The __ refers to the configuration setting for whether trunking should be used. Each interface also has an __, which refers to what is currently happening on the interface, and might have been chosen by DTP’s negotiation with the other device.
switchport mode
Cisco switches use the __ interface subcommand to define the administrative trunking mode.
access
Always act as an access (nontrunk) port
trunk
Always act as a trunk port
dynamic desirable
Initiates negotiation messages and responds to negotiation messages to dynamically choose whether to start using trunking
dynamic auto
Passively waits to receive trunk negotiation messages, at which point the switch will respond and negotiate whether to use trunking
dynamic auto, dynamic desirable
Both (2960) switches default to an administrative mode of __, meaning that neither switch initiates the trunk negotiation process. By changing one switch to use __ mode, which does initiate the negotiation, the switches negotiate to use trunking, specifically 802.1Q.
Dynamic auto
__ tells both switches to sit there and wait on the other switch to start the negotiations.
show interfaces trunk
This command lists information about all interfaces that currently operationally trunk; that is, it list interfaces that currently use VLAN trunking.
access
Dynamic Auto - Access
access
Dynamic Auto - Dynamic Auto
trunk
Dynamic Auto - Trunk
trunk
Dynamic Auto - Dynamic Desirable
do not use
Access - Trunk
allowed VLAN list
The __ feature provides a mechanism for engineers to administratively disable a VLAN from a trunk.
switchport trunk allowed vlan {add | all | except | remove} vlan-list
By default, switches include all possible VLANs (1–4094) in each trunk’s allowed VLAN list. However, the engineer can then limit the VLANs allowed on the trunk by using the following interface subcommand:
switchport trunk allowed vlan except 100-200
The __ interface subcommand adds VLANs 1 through 99 and 201 through 4094 to the existing allowed VLAN list on that trunk.
vlan {vlan-id}
If a switch does not know that a VLAN exists—for example, if the switch does not have a __ command configured.
shutdown vlan {vlan-id}
VLAN can exist in a switch’s configuration, but also be administratively shut down either by using the __ global configuration command.
VTP
A VLAN has been automatically pruned by __.
STP instance
A VLAN’s __ has placed the trunk interface into a blocking state.
allowed VLAN list
A VLAN has been removed from the trunk’s __.