CCNA Cram ch. 6
When a DHCP-enabled client first boots up, what does the client broadcast?
The client broadcasts a DHCPDISCOVER message on the local subnet. The destination address of DHCPDISCPOVER messages is 255.255.255.255.
In 802.1Q, what is the native VLAN?
The native VLAN is VLAN1 by default. 802.1Q does not tag the native VLAN across trunk links.
True or False: Access between VLANs is not possible without a functioning Layer 3 process.
True
How do you implement a VLAN?
1. Create the VLAN. 2. Name the VLAN (optional, but expected). 3. Assign switch ports to the VLAN.
What is a VLAN?
A VLAN can be defined as a virtual broadcast domain. Instead of segmenting the broadcast domain with routers at Layer 3, you segment using switches at Layer 2.
What is a multicast?
A message sent by one host and intended for a specific group of other hosts.
What are the three operations performed by a bridge or switch? A. Filter, copy, frame B. Broadcast, multicast, unicast C. Filter, forward, flood D. Filter, forward, broadcast
Answer C is correct. Switches will filter (drop) a frame of the source and destination MAC addresses are on the same port, forward the frame out a single port if the destination MAC is known in the MAC table, or flood the frame out all ports (except the one it was received on) if the destination MAC is not in the MAC table or it is a broadcast frame (or, by default, if it is a multicast frame).
What is the definition of collision domain? A. A DNS domain in which IP address conflicts occur. B. A set of devices that hear broadcasts caused by collisions. C. Collision domains only exist when using coaxial media. D. A set of devices that cause and are affected by one another's collisions.
Answer D is correct.
What is the relationship between VLANs and IP subnets? A. VLANs have no relationship to IP subnets. B. All VLANS must be in the same IP subnet. C. If subnets are in use, VLANs cannot be used. D. Each VLAN must be numbered to match the IP subnet network ID. E. Each VLAN must use a separate IP subnet. F. In a Frame Relay WAN environment, there must be an equal number of VLANs and subnets.
Answer E is correct. Therefore, Answers A and B are wrong. Answer C is incorrect. Answer D is not required, but we often do this to save confusion. Answer F sounds good, but remember that VLANs do not extend into traditional WAN circuits like Frame Relay.
What are three benefits of using VLANs? A. Complexity B. Security C. Obscurity D. Flexibility E. Limitation of broadcast impact F. Higher speeds G. Extended cable range H. Better mileage
Answers B, D, and E are correct.
What are the three duplex configurations?
Auto, Full, or Half
Cons of Cut-Through switching mode.
Bad frames will be switched along with the good
What command allows you to view information that is specific to VLAN 10?
Cat2960# show vlan id 10 VLAN Name Status Ports ---------------------- --------- ------------------------------- 10 sales active Fa0/1, Fa0/3, Fa0/4, Fa0/5 Fa0/6, Fa0/7, Fa0/8, Fa0/9 Fa0/10, Fa0/11, Fa0/12 <text omitted>
What does "switchport nonegotiate" do?
Disables DTP. A trunk will form only if the neighbor switch port is set to On (mode trunk). DTP frames are not sent or acknowledged.
What is DHCP?
Dynamic Host Configuration Protocol (DHCP) allows a host to obtain an IP address automatically and to set TCP/IP stack configuration parameters such as subnet mask, default gateway, and DNS addresses from a DHCP server.
What is DTP?
Dynamic Trunking Protocol (DTP) is a Cisco-proprietary, point-to-point Layer 2 protocol that manages trunk negotiation. Switches from other vendors do not support DTP. DTP is enabled by default on a switch port when certain trunking modes are configured on the switch port. DTP manages trunk negotiation only if the port on the other switch is configured in a trunk mode that supports DTP.
What does a broadcast MAC address look like?
FF-FF-FF-FF-FF-FF
What is a runt?
Frames that are smaller than 64 bytes are called runts.
What is included in a DHCPOFFER message?
In a DHCPOFFER message, initial IP configuration for the client, such as IP address, subnet mask, and default gateway, is included. A DHCPOFFER message originates from the DHCP server.
Where are the VLAN configs stored?
It is stored in flash memory in a special file called vlan.dat.
What is Store-and-Forward switching mode?
It is the basic mode that bridges and switches use In store-and-forward switching, the entire frame is buffered (copied into memory) and a cyclic redundancy check (CRC) is run to compare the frame's FCS value with the CRC output value..
Where is the MAC address table stored?
RAM
What is the IEEE-standard for trunking?
802.1Q referred to as "dot1q"
A switch port can be in one of five modes:
Access (a.k.a. "off"): switchport mode access Trunk (a.k.a. "on"): switchport mode trunk NoNegotiate: switchport nonegotiate (Dynamic) Desirable: switchport mode dynamic desirable (Dynamic) Auto: switchport mode dynamic auto
What does "switchport mode access" do?
In access mode, the port is an access port and will not trunk, even if the neighbor switch wants to. This mode is intended for the connection of single hosts or hubs.
What does "switchport mode trunk" do?
In trunk mode, the port will trunk unconditionally, and trunk connectivity will happen if the neighbor switch port is set to Auto, Desirable, or NoNegotiate. Will only form if a request is received from the other switch.
To break up broadcast domains, you need a...
Layer 3 device: a router
What are the default Layer 2 Ethernet interface VLAN settings on a Catalyst 2960 switch?
The default Layer 2 Ethernet interface VLAN settings on a Catalyst 2960 switch are as follows: Interface mode: switchport mode dynamic auto Trunking Encapsulation Type: dot1q Negotiation of Trunking: On Trunking VLANs: All allowed Default VLAN: VLAN 1 VLAN pruning eligible range: 2 to 1001 Native VLAN: 1 The switchport mode dynamic auto command allows the interface to convert the interface from an access link to a trunk link. The interface becomes a trunk if the neighboring interface is set to trunk or desirable.
Pros of Cut-Through switching mode.
The fastest switching mode No time is spent running the CRC The frame is forwarded as fast as possible
What does "switchport mode dynamic auto" do?
The port trunks only in response to a DTP request to do so. A trunk forms with a neighbor port set to on or desirable. DTP frames are not sent but are acknowledged if received.
What IOS commands display information on all configured VLANs?
The show vlan {name vlan-name | id id} command and the show vlan brief command display information on all configured VLANs. In addition to displaying all information on configured VLANs, the show vlan and show vlan brief commands display the switch interfaces that are assigned to each VLAN.
What is Cut-Through switching mode?
The switch analyzes the first 6 bytes after the preamble. Those 6 bytes are the destination MAC address.
What are the three solutions for inter-VLAN routing?
The three solutions for inter-VLAN communication are Using a router with a separate interface for each VLAN A router on a stick A Layer 3 switch
True or False, bridges can support ports with varying speeds.
False. A bridge's ports must all be the same speed.
True or False: A switch populates its MAC address table with the destination MAC address of frames received on each port.
False. A switch populates the MAC table using the source MAC address of frames received on each port.
True or False: For security reasons, all switch ports are assigned an unused VLAN by default.
False. By default, all switch ports are assigned to VLAN 1, and are fully functional; therefore, VLAN 1 is in use.
True or False. By default, the only VLANs that are allowed on a trunk port are the ones that you assign.
False. By default, traffic from all VLANs is allowed on a trunk.
True or False. Switches only look at the destination MAC to build their MAC table.
False. Switches examine the source and destination MAC in a frame to build their MAC table and make their forwarding decision.
What is Fragment-Free switching mode?
Fragment-free mode is a switching method that picks a compromise between the reliability of store-and-forward mode and the speed of cut-through mode. If the frame is less than 64 bytes, it is discarded.
Trunk links allow the switch to carry multiple VLANs across a single link. By default, each port on a switch belongs to VLAN 1. For devices that are in a VLAN (that spans multiple switches) to talk to other devices in the same VLAN, you must use trunking or have a dedicated port for each VLAN. Trunk links encapsulate frames using a Layer 2 protocol. This encapsulation contains information for a switch to distinguish traffic from different VLANs and to deliver frames to the proper VLANs. The Catalyst 2960 supports 802.1Q as its trunking protocol.
IEEE 802.1Q tagging provides an industry-standard method of identifying frames that belong to a particular VLAN. 802.1Q does this by using an internal tag that modifies the existing Ethernet frame with the VLAN identification.
What is VLAN membership?
VLAN membership describes which VLAN a port on a switch is assigned.
What are VLANs?
VLANs are broadcast domains in a Layer 2 network. Each VLAN is like a distinct virtual bridge within the switch. Each virtual bridge you create in a switch defines a broadcast domain. By default, traffic from one VLAN cannot pass to another VLAN. Each of the users in a VLAN would also be in the same IP subnet. By default, each access port can belong to only one data VLAN.
What are three rules of VLAN's?
VLANs logically divide a switch into multiple, independent switches at Layer 2. Each VLAN is its own broadcast domain. Each VLAN should be in its own subnet.
What is a frame of 1522 bytes referred to as?
"baby giant" of 1522 bytes
Dynamically-learned MAC entries have a default max age timer of...
300 seconds (5 min)
When configuring trunking on a Catalyst 2960, what are the four Layer 2 interface modes supported?
switchport mode access: Makes the interface a nontrunking access port. switchport mode dynamic auto: Allows the interface to convert to a trunk link if the connecting neighbor interface is set to trunk or desirable. switchport mode dynamic desirable: Makes the interface attempt to convert the link to a trunk link. The link becomes a trunk if the neighbor interface is set to trunk, desirable, or auto. switchport mode trunk: Configures the port to permanent trunk mode and negotiates with the connected device if the other side can convert the link to trunk mode.
Switching loops create three major problems:
► Broadcast storms: Switches must flood broadcasts, so a looped topology will create multiple copies of a single broadcast and perpetually cycle them through the loop. ► MAC table instability: Loops make it appear that a single MAC address is reachable on multiple ports of a switch, and the switch is constantly updating the MAC table. ► Duplicate frames: Because there are multiple paths to a single MAC, it is possible that a frame could be duplicated to be flooded out all paths to a single destination MAC.
What are the advantages of VLANs?
► Increase the number of broadcast domains while reducing their size. ► Provide additional security. ► Increase the flexibility of network equipment. ► Allow a logical grouping of users by function, not location. ► Make user adds, moves, and changes easier.
For VLANs to communicate with each other, what network component is needed?
A router or Layer 3 switch is needed for inter-VLAN communication. It is important to think of a VLAN as a distinct virtual bridge in a switch, with is its own IP subnet and broadcast domain. A network device cannot communicate from one IP subnet to another without a router. The same is true for a VLAN; you cannot communicate from one VLAN to another without a router-capable device.
A business-class switch must do three things:
Address learning Frame forwarding Layer 2 loop removal
What is the difference between connecting 2 switches between an ordinary connection (an access port) and a trunk port?
Although an access port is only in one data VLAN at a time, a trunk port has the job of carrying traffic for all VLANs from one switch to another. Any time you connect a switch to another switch, you want to make it a trunk.
Rob and Lorena are discussing the behavior and capabilities of trunks. Rob tells Lorena that traffic from all VLANs is allowed across an 802.1Q trunk by default, but when Lorena asks how the traffic is kept in its correct VLAN when it is received at the port at the other end of the trunk, Rob has trouble explaining the mechanism. Which of the following best explains how frames from multiple VLANs are transmitted across a single trunk link and are properly distributed into the correct VLAN at the receiving switch? A. Each frame (with the exception of frames in the native VLAN) is marked with its VLAN ID using a 4-byte tag, which also necessitates the recalculation of the FCS. Correct redistribution is accomplished at the receiving end by analysis of the frame header information, in which the tag encodes the destination VLAN. B. The frames are each assigned a fragmentation number so they can be easily reassembled in order at the receiving end. C. The frames are sent on a clocked circuit; by keeping track of the clock markings on the frames, the correct distribution can be guaranteed. D. All frames are assigned a number based on the Copeland-Summers algorithm, which allows them to be properly encoded at the destination
Answer A is correct. Answer B is incorrect because fragmentation is done at the packet level and has nothing to do with trunking. Answer C is wrong, intentionally misleading you by mixing in serial WAN terminology. Answer D is fictitious
Which of the following is an advantage of switches over hubs? A. Switches provide full-duplex microsegmentation of collision domains. B. The low cost of switches compared to hubs makes them an attractive choice for growing businesses. C. Although they cannot segment broadcast domains, the much greater speed of switches still makes them a desirable upgrade. D. Switches are impervious to security threats by definition and provide a secure Layer 2 solution out of the box.
Answer A is correct. Switches, when they are configured correctly, can eliminate collisions from the LAN. This design of creating a single collision domain for each connected device is called microsegmentation.
John explains the concept of the Native VLAN to you. To prove you understand it, choose the correct explanation from the following. A. The native VLAN is the VLAN assigned to interface VLAN 1. B. The native VLAN is the VLAN into which frames will be switched, if they arrive at a trunk interface untagged. C. The native VLAN is the one assigned to the trunk interface. D. The native VLAN is not longer supported by Cisco switches.
Answer B in this case. Answer A is misleading because it is sometimes true—but it is not a requirement or definition of the native VLAN. Answer C cannot be true because by definition a trunk is in all VLANs, it is not an access port that is always assigned to one VLAN.
Building a fully redundant switched network involves installing switches with redundant connections. Doing so creates the possibility of switching loops, broadcast storms, duplicate frame transmission, and MAC table instability. What works to avoid these undesirable consequences? A. Disconnect redundant links until they are needed upon network failure. B. The default STP feature will eliminate switching loops automatically. C. The optional Spanning Tree Protocol can be installed and manually configured to respond to switching loops. D. Upgrade all switches to Layer 3 switches, a more modern technology that automatically eliminates switching loops.
Answer B is correct. Answer A may be correct, but is really an unacceptable answer and certainly not the best answer. Answer C is incorrect; STP is installed and operating by default. Enhancements and tuning may be manually configured. Answer D is incorrect; upgrading to a Layer 3 switch will not eliminate collisions, although like Layer 2 switches they can be configured to do so.
Which of the following explains why full-duplex operation is desirable? A. Full duplex allows for the detection of collisions so that data can be retransmitted when the wire is free. B. Full duplex allows simultaneous transmit and receive functions, providing higher overall throughput. C. Full duplex provides inter-VLAN routing capability. D. Full duplex can take advantage of existing coaxial cabling.
Answer B is correct. Full duplex uses two wire pairs or two optical fibers to establish separate send and receive circuits, effectively doubling potential throughput.
What is the function of 802.1D STP? A. Prevents routing loops in redundant topologies B. Prevents Layer 2 loops in networks with redundant switched paths C. Prevents frame forwarding until all IP addresses are known D. Enables the use of multiple routed paths for load-sharing E. Allows the propagation of VLAN information from a central source
Answer B is correct. STP prevents Layer 2 loops if redundant paths exist.
Which switching mode sacrifices speed for error-free switching? A. Segment-free mode B. Store-and-forward mode C. Cut-throat mode D. Fragment-free mode E. Cut-through mode
Answer B is correct. Store-and-forward mode is the slowest mode but has the advantage of fully error checking every frame for reliability. Fragment-free mode examines the first 64 bytes of every frame for increased reliability, but is not as fast as cut-through mode.
You currently have seven hubs that form the LAN in your office, to connect 12 servers and 30 users. You have the budget to buy one 24-port switch. What is the most efficient way to utilize your limited switch resources? A. Connect all the hubs to each other, and then connect the string of hubs to one switch port. B. Connect each hub to a single switch port. C. Connect each hub to a single switch port. Move the servers to their own switch ports. Move active user PCs to the remaining switch ports, leaving the less-active PCs attached to hubs. Distribute the remaining PCs evenly across the hubs. D. Connect each hub to the switch with two or three cables to provide additional bandwidth.
Answer C is correct. Doing this will ensure that the most important devices have the best possible data access speed.
Collisions are an expected part of how Ethernet was designed to work. Unfortunately, they cause congestion, loss and delay, especially as the network gets larger and busier. Bridges (and subsequently switches) were designed to eliminate the problem of collisions. How do they do that? A. Switches use CSMA/CA to arbitrate which device is allowed to send so that collisions do not happen. B. Switches process frames so fast that although collisions still happen, they take less time to clear and their impact is greatly reduced. C. Switches filter, forward, or flood frames based on the destination MAC address in the frame received on each port, which completely eliminates collisions. D. Switches support full-duplex cabling on UTP, which allows a simultaneous send and receive which completely eliminates collisions.
Answer D is correct. A is incorrect; CSMA/CA is a feature of wireless access points, but not switches. Answer B is incorrect; if collisions are happening, the switch has little to with how fast they are cleared. Answer C is a correct statement but does not answer the question; switches can still function as a switch as described in this answer, while collisions are happening.
Which configuration correctly places interface Gi0/24 in VLAN 111? A. Switch(config)#int f0/24 Switch(config-if)#switch port access vlan 111 B. Switch(config)#int f0/24 Switch(config-if)#switchport access vlan 111 C. Switch(config)#int gi0/24 Switch(config-if)#switch port access vlan 111 D. Switch(config)#int gi0/24 Switch(config-if)#switchport access vlan 111
Answer D is correct. Answer A is wrong because it configures the wrong interface and the switchport command has a space in it. Answer B is incorrect because it configures the wrong interface. Answer C is incorrect because switchport command has a space in it.
How many collision and broadcast domains exist on a 12-port switch with default configuration? A. 2 collision domains, 12 broadcast domains B. 1 collision domain, 12 broadcast domains C. 1 collision domain, 1 broadcast domain D. 12 collision domains, 1 broadcast domain
Answer D is correct. Each port on a switch is a collision domain. A switch creates one broadcast domain.
What is the most common Layer 2 device? A. Hub B. Repeater C. Router D. Switch E. Bridge
Answer D is correct. Switches are by far the most common Layer 2 device in use. Answers A, B, and C are incorrect because hubs, repeaters, and routers are not Layer 2 devices. (Hubs and repeaters are Layer 1; routers are Layer 3.)
What happens when a switch receives a frame with the destination MAC address of FF-FF-FF-FF-FF-FF? A. The switch drops the frame and sends a "Destination Unreachable" message back to the source. B. The switch forwards the frame out the port that connects to the host with that MAC address. C. The switch filters the frame because the address is not valid. D. The switch floods the frame out all ports except the one it came in on.
Answer D is correct. The MAC address shown is the broadcast address, so the switch will perform the flood operation.
What devices and functions can an administrator use to segment the network, assuming that no VLANs are used? Choose all that apply. A. Routers to segment broadcast domains B. Switches to segment broadcast domains C. Switches to increase the number of collision domains D. Bridges to segment collision domains E. Hubs to segment collision domains F. Bridges to segment broadcast domains G. Repeaters to segment broadcast domains
Answers A, C, and D are correct. Routers segment broadcast domains; switches and bridges segment (increase the number of) collision domains. Answers B, E, F, and G are incorrect. The question stipulates that VLANs are not in use, so a switch does not segment broadcast domains. Hubs and repeaters extend and enlarge, not segment, collision and broadcast domains.
Which of the following are true of switches and bridges? Choose all that apply. A. Switches have fewer ports and switch in software. B. Switches have a higher port density and switch using ASIC hardware. C. Bridges are faster than switches. D. Switches are faster than bridges. E. Switches create only one broadcast domain by default. F. Bridges create only one broadcast domain.
Answers B, D, E, and F are correct. Switches have more ports than bridges and are faster than bridges. Watch out for the trick: Both switches and bridges create only one broadcast domain.
Which of the following DTP mode pairings will form a trunk? Choose all that apply. A. Trunk and access B. Dynamic desirable and NoNegotiate C. Dynamic auto and trunk D. Dynamic auto and dynamic desirable
Answers C and D are the pairs that will trunk. Answer A will not because one side is access, which will never trunk. Answer B will not because dynamic desirable needs to hear a response to the negotiation, and NoNegotiate will never respond.
How do you display the trunking interfaces on a Catalyst 2960 switch?
Cat2960# show interfaces trunk Port Mode Encapsulation Status Native vlan Gi0/1 on 802.1q trunking 1 Port Vlans allowed on trunk Gi0/1 1-4094 Port Vlans allowed and active in management domain Gi0/1 1-3,5,10,20,30,40,50,60 Port Vlans in spanning tree forwarding state and not pruned Gi0/1 1-3,5,40
What IOS commands assign interface g0/1 to VLAN 10 and interface g0/2 to VLAN 20?
Cat2960(config)# int g0/1 Cat2960(config-if)# switchport access vlan 10 Cat2960(config-if)# int g0/2 Cat2960(config-if)# switchport access vlan 20 The switchport access vlan vlan-ID interface command assigns an interface to a VLAN.
How do you configure an interface for trunking on a Catalyst 2960 switch?
Cat2960(config)# interface g0/1 Cat2960(config-if)# switchport mode trunk Cat2960(config-if)# interface g0/2 Cat2960(config-if)# switchport mode dynamic desirable
As a network administrator, you want to add gigabit interfaces 1 through 12 to VLAN 10 on your Catalyst 2960 switch. How do you statically assign these ports to VLAN 10?
Cat2960(config)# interface range g 0/1 - 12 Cat2960(config-if-range)# switchport mode access Cat2960(config-if-range)# switchport access vlan 10 You can assign one interface or a range of interfaces at a time to a VLAN. To assign a range of interfaces to a VLAN, first enter the interface range you want to configure. Then define the interfaces as access ports with the switchport mode access command. To finish, you will need to assign the range of ports to the desired VLAN with the switchport access vlan vlan-id interface command. When using the interface range command, take notice of the prompt change to config-if-range.
As a network administrator, you want to create two VLANs, one named Admin and the other named Sales. What commands will create the two VLANs using VLAN ID 10 for the Admin VLAN and VLAN ID 20 for the Sales VLAN?
Cat2960(config)# vlan 10 Cat2960(config-vlan)# name Admin Cat2960(config-vlan)# vlan 20 Cat2960(config-vlan)# name Sales
MAC address table is also know as...
Content-addressable memory [CAM] table
What is the fastest switching mode?
Cut-Through Mode
Guy bets you five bucks that he can create a trunk between two 2960s without configuring the two switches being trunked—all he needs is a crossover cable. Should you take the bet?
Dynamic Trunking Protocol is running by default, and every port is in DTP mode Dynamic Auto, which will not negotiate to trunking together.
What are extended-range VLANs?
Extended-range VLANs are VLANs with VLAN IDs from 1006 to 4094. Extended-range VLANs can only be configured if the switch is in VTP transparent mode with the appropriate IOS licensing installed
True or False, bridges support full duplex.
False
How do you enable routing between VLANs on a router on a stick?
RouterB(config)# int g0/0 RouterB(config-if)# ip address 192.168.1.1 255.255.255.0 RouterB(config-if)# int g0/0.10 RouterB(config-if)# ip address 192.168.10.1 255.255.255.0 RouterB(config-if)# encapsulation dot1q 10 RouterB(config-if)# int g0/0.20 RouterB(config-if)# ip address 192.168.20.1 255.255.255.0 RouterB(config-if)# encapsulation dot1q 20
What are the six characteristics of a typical VLAN setup?
Six characteristics of a typical VLAN setup are as follows: Each logical VLAN is like a separate physical bridge. For different VLANs to communicate with each other, traffic must be forwarded through a router or Layer 3 switch. Each VLAN is considered to be a separate logical network. VLANs can span multiple switches. Each VLAN is a separate broadcast domain. VLANs can enhance security by logically segmenting a network.
This is a protocol that runs on bridges and switches to find and block redundant looped paths during normal operation.
Spanning Tree Protocol (STP)
How do you verify the VLANs on a Catalyst switch and the ports assigned to each VLAN?
Switch# show vlan brief VLAN Name Status Ports ---- ------------------- --------- ---------------------------- 1 default active Gi0/2 10 InternetAccess active 20 Operations active Fa0/1, Fa0/2, 30 Administration active Fa0/6, Fa0/7, Fa0/8, Fa0/9 40 Engineering active Fa0/3, Fa0/4, Fa0/5, Fa0/10, Fa0/11, Fa0/12, Fa0/13,Fa0/14, Fa0/15, Fa0/16, Fa0/17, Fa0/18, Fa0/19,Fa0/20 60 Public active Fa0/21, Fa0/22, Fa0/23, Fa0/24 !text-omitted!
Configure a Catalyst 2960 switch with VLAN number 10 and name the VLAN "Accounting."
Switch(config)# vlan 10 Switch(config-vlan)# name Accounting
What are the three ways that inter-VLAN communication can be established?
The three ways that inter-VLAN communication can be established are as follows: Router on a stick: Involves a single connection, called a trunk link, from the switch to a router. The trunk link uses a trunking protocol to differentiate between VLANs. Router with a separate interface in each VLAN. Layer 3 switch.
What are two methods to assign a port to a VLAN?
The two methods to assign a port to a VLAN are as follows: Statically: Statically assigning a port to a VLAN is a manual process performed by the administrator. Dynamically: VLAN Membership Policy Server (VMPS) allows you to define VLAN membership through the MAC address. Security products such as Cisco ISE allow you to set ports on VLANs based on the type of endpoint that connects to the port.
What does "switchport mode dynamic desirable" do?
This mode actively solicits a trunk connection with the neighbor. DTP frames are sent and responded to if received. A trunk forms if the neighbor is set to On, Desirable, or Auto. If the neighbor is set to NoNegotiate, the trunk will not form because Desirable needs a response from the neighbor, which NoNegotiate will not send.
Your CCNA study partner argues that it is okay to have multiple VLANs use the same IP subnet. Are they correct? A. Yes B. No
This person is wrong.
Because VLANs are considered individual broadcast domains, for inter-VLAN communication to occur, a Layer 3 device is needed. What three things must occur for inter-VLAN routing?
Three requirements for inter-VLAN routing to occur are as follows: The router must know how to reach all VLANs. The routers must have a separate physical connection for each VLAN, or trunking must be enabled on a single physical connection. The use of a Layer 3 switch if no router is being used.
To enable inter-VLAN routing using a Layer 3 switch, what must be configured on the Layer 3 switch?
To enable a Layer 3 switch to perform inter-VLAN routing, Switch Virtual Interfaces (SVI) on the switch need to be configured, IP routing must be enabled, VLANs must be configured on the switch, and at least one physical port must support the VLANs to be routed.
What are three ways to verify the ports assigned to VLANs?
To verify that a port is assigned to a VLAN, you could use the show vlan (and its applicable extensions), show interface type number, show running-config (and it applicable extensions), show interface status, and show mac-address-table commands.
What are trunk links?
Trunk links allow the switch to carry multiple VLANs across a single link. By default, each port on a switch belongs to VLAN 1. For devices that are in a VLAN (that spans multiple switches) to talk to other devices in the same VLAN, you must use trunking or have a dedicated port for each VLAN. Trunk links encapsulate frames using a Layer 2 protocol. This encapsulation contains information for a switch to distinguish traffic from different VLANs and to deliver frames to the proper VLANs. The Catalyst 2960 supports 802.1Q as its trunking protocol.
Because a DHCPDISCOVER message is a broadcast, a router will not forward DHCPDISCOVER messages. If a client is on a different IP subnet than the DHCP server, how do you forward the DHCPDISCOVER message form the client to the DHCP server?
You forward the DHCPDISCOVER message by issuing the ip helper-address dhcpserver-address interface command on the remote router. The ip helper-address global configuration command is entered on the router that the remote host is directly connected to.
