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NEW QUESTION NO: 6
Which of the following prefixes will an IPv6enabled computer use to automatically configure an IPv6 address for itself?A. 2000::/3
B. FC00::/7
C. FE80::/10
D. FF00::/8
Answer: C
Explanation/Reference:
Section: Addressing and Routing Protocols in an Existing Network Explanation Explanation:
An IP version 6 (IPv6) enabled computer will use the prefix FE80::/10 to automatically configure an IPv6 address for itself. The IPv6 prefix FE80::/10 is used for unicast link-local addresses. IPv6 addresses in the FE80::/10 range begin with the characters FE80 through FEBF. Unicast packets are used for one-to-one communication. Link-local addresses are unique only on the local segment. Therefore, link-local addresses are not routable. Unicast link-local addresses are used for neighbor discovery and for environments in which no router is present to provide a routable IPv6 prefix.
IPv6 was developed to address the lack of available address space with IPv4. An IPv6 address is a 128bit (16byte) address that is typically written as eight groups of four hexadecimal characters, including numbers from 0 through 9 and letters from A through F.
Each group of four characters is separated by colons.
Leading zeroes in each group can be dropped. A double colon can be used at the beginning, middle, or end of an IPv6 address in place of one or more contiguous four character groups consisting of all zeroes.
However, only one double colon can be used in an IPv6 address. Therefore, the following IPv6 addresses are equivalent:
FE80:0000:0000:070D:0000:50A0:0001:0024
FE80::070D:0000:50A0:0001:0024
FE80:0:0:70D:0:50A0:1:24
FE80::70D:0:50A0:1:24
An IPv6enabled computer will not use the prefix 2000::/3 to automatically configure an IPv6 address for itself. The IPv6 prefix 2000::/3 is used for global aggregatable unicast addresses. IPv6 addresses in the
2000::/3 range begin with the characters 2000 through 3FFF. Global aggregatable unicast address prefixes are distributed by the Internet Assigned Numbers Authority (IANA) and are globally routable over the Internet. Because there is an inherent hierarchy in the aggregatable global address scheme, these addresses lend themselves to simple consolidation, which greatly reduces the complexity of Internet routing tables.
An IPv6enabled computer will not use the prefix FC00::/7 to automatically configure an IPv6 address for itself. The IPv6 prefix FC00::/7 is used for unicast unique-local addresses. IPv6 addresses in this range begin with the characters FC00 through FDFF. Unique-local addresses are not globally routable, but they are routable within an organization.
An IPv6enabled computer will not use the prefix FF00::/8 to automatically configure an IPv6 address for itself. The IPv6 prefix FF00::/8 is used for multicast addresses, which are used for one-to-many communication. IPv6 addresses in the FF00::/8 range begin with the characters FF00 through FFFF.
However, certain address ranges are used to indicate the scope of the multicast address. The following IPv6 multicast scopes are defined:
FF01::/16 -nodelocal
FF02::/16 -linklocal
FF05::/16 -uniquelocal
FF08::/16 -organizationlocal
FF0E::/16 -global
Reference:
CCDA 200-310 Official Cert Guide, Chapter 9, LinkLocal Addresses, p. 343 CCDA 200-310 Official Cert Guide, Chapter 9, SLAAC of LinkLocal Address, p. 350 Cisco: IPv6: A Primer for Physical Security Professionals
NEW QUESTION NO: 7
DRAG DROP
Select the protocols and port numbers from the left, and drag them to the corresponding traffic types on the right. Not all protocols and port numbers will be used.
Select and Place:
Answer:
Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
Lightweight Access Point Protocol (LWAPP) uses User Datagram Protocol (UDP) port 12222 for data traffic and UDP port 12223 for control traffic. LWAPP is a protocol developed by Cisco and is used as part of the Cisco Unified Wireless Network architecture. LWAPP creates a tunnel between a lightweight access point (LAP) and a wireless LAN controller (WLC)? in LWAPP operations, both a LAP and a WLC are required. The WLC handles many of the management functions for the link, such as user authentication and security policy management, whereas the LAP handles real-time operations, such as sending and receiving 802.11 frames, wireless encryption, access point (AP) beacons, and probe messages. Cisco WLC devices prior to software version 5.2 use LWAPP.
Control and Provisioning of Wireless Access Points (CAPWAP) uses UDP port 5246 for control traffic and UDP port 5247 for data traffic. CAPWAP is a standards-based version of LWAPP. Cisco WLC devices that run software version 5.2 and later use CAPWAP instead of LWAPP.
Neither LWAPP nor CAPWAP use Transmission Control Protocol (TCP) for communication. TCP is a connection-oriented protocol. Because UDP is a connectionless protocol, it does not have the additional connection overhead that TCP has? therefore, UDP is faster but less reliable.
Reference:
Cisco: LWAPP Traffic Study
IETF: RFC 5415: Control And Provisioning of Wireless Access Points (CAPWAP) Protocol Specification
NEW QUESTION NO: 8
Which of the following queuing methods is the most appropriate for handling voice, video, mission-critical, and lower-priority traffic?
A. FIFO
B. WFQ
C. LLQ
D. CBWFQ
Answer: C
Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
Of the choices provided, low-latency queuing (LLQ) is the most appropriate queuing method for handling voice, video, mission-critical, and lower-priority traffic. LLQ supports the creation of up to 64 user-defined traffic classes as well as one or more strict-priority queues that can be used to guarantee bandwidth for delay-sensitive traffic, such as voice and video traffic. Each strict-priority queue can use as much bandwidth as possible but can use only the guaranteed bandwidth when other queues have traffic to send, thereby avoiding bandwidth starvation. Cisco recommends limiting the strict-priority queues to a total of 33 percent of the link capacity.
Class-based weighted fair queuing (CBWFQ) provides bandwidth guarantees, so it can be used for voice, video, mission-critical, and lower-priority traffic. However, CBWFQ does not provide the delay guarantees provided by LLQ, because CBWFQ does not provide support for strict-priority queues. CBWFQ improves upon weighted fair queuing (WFQ) by enabling the creation of up to 64 custom traffic classes, each with a guaranteed minimum bandwidth.
Although WFQ can be used for voice, video, mission-critical, and lower-priority traffic, it does not provide the bandwidth guarantees or the strict-priority queues that are provided by LLQ. WFQ is used by default on Cisco routers for serial interfaces at 2.048 Mbps or lower. Traffic flows are identified by WFQ based on source and destination IP address, port number, protocol number, and Type of Service (ToS). Although WFQ is easy to configure, it is not supported on high-speed links.
First-in-first-out (FIFO) queuing is the least appropriate for voice, video, mission-critical, and lower-priority traffic. By default, Cisco uses FIFO queuing for interfaces faster than 2.048 Mbps. FIFO queuing requires no configuration because all packets are arranged into a single queue. As the name implies, the first packet received is the first packet transmitted, without regard for packet type, protocol, or priority.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 6, Low-Latency Queuing, p. 235 Cisco: Enterprise QoS Solution Reference Network Design Guide: Queuing and Dropping Principles Cisco: Signalling Overview: RSVP Support for Low Latency Queueing
NEW QUESTION NO: 9
View the Exhibit.
Refer to the exhibit. Which of the following traffic flows will the IPS be unable to monitor? (Choose two.)
A. traffic from the DMZ to the Internet
B. traffic from the DMZ to the LAN
C. traffic from the Internet to the DMZ
D. traffic from the Internet to the LAN
E. traffic from the LAN to the DMZ
F. traffic from the LAN to the Internet
Answer: B,E
Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
The Intrusion Prevention System (IPS) in this scenario will be unable to monitor traffic flows from the demilitarized zone (DMZ) to the LAN and from the LAN to the DMZ. An IPS provides real-time monitoring of malicious traffic and can prevent malicious traffic from infiltrating the network. An IPS functions similarly to a Layer 2 bridge; a packet entering an interface on the IPS is directed to the appropriate outbound interface without regard to the packet's Layer 3 information. Instead, the IPS uses interface or virtual LAN (VLAN) pairs to determine where to send the packet. This enables an IPS to be inserted into an existing network topology without requiring any disruptive addressing changes. Because traffic flows through an IPS, an IPS can detect malicious traffic as it enters the IPS device and can prevent the malicious traffic from infiltrating the network.
In this scenario, the IPS is deployed inline between the firewall and the edge router. Because traffic flows between the LAN and DMZ do not pass through the firewall, the IPS will be unable to monitor them.
However, the IPS will be able to monitor traffic flows between the LAN and the Internet and between the DMZ and the Internet. In addition, because the IPS is deployed on the outside of the firewall, it will have visibility into traffic flows that will ultimately be dropped by the firewall. This insight can be useful during an active attack; however, it comes at the cost of additional resource utilization since the IPS will be processing more traffic than will ultimately be passing through the firewall.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 13, IPS/IDS Fundamentals, pp. 534-535
NEW QUESTION NO: 10
Which of the following statements are true regarding the function of the LAP in the Cisco Unified Wireless Network architecture? (Choose three.)
A. The LAP determines which RF channel should be used to transmit 802.11 frames.
B. The LAP supports 802.11 encryption.
C. The LAP must be located on the same subnet as a WLC.
D. The LAP maintains associations with client computers.
E. The LAP can function without a WLC.
F. The LAP should be connected to an access port on a switch.
Answer: B,D,F
Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
In the Cisco Unified Wireless Network architecture, a lightweight access point (LAP) supports 802.11 encryption, maintains associations with client computers, and should be connected to an access port on a switch. A LAP creates a Lightweight Access Point Protocol (LWAPP) tunnel between itself and a wireless LAN controller (WLC)? in LWAPP operations, both a LAP and a WLC are required. The WLC handles many of the management functions for the link, such as user authentication and security policy management, while the LAP handles real-time operations, such as sending and receiving 802.11 frames, wireless encryption, access point (AP) beacons, and probe messages.
When connecting a LAP to a network, you should connect the LAP to an access port on a switch, not to a trunk port. Because the WLC handles the management functions for LWAPP operations, the LAP cannot begin associating with client computers unless a WLC is available on the network. Therefore, the LAP must associate with a WLC after it is connected to the network. After connecting to a WLC and obtaining its configuration information, the LAP can begin associating with clients. The LAP can receive encrypted or unencrypted 802.11 frames. The WLC, however, does not support 802.11 encryption; as the data passes through the LAP, it is decrypted and then sent to the WLC for further forwarding.
It is not necessary for the LAP to be located on the same subnet or even in the same geographic area as a WLC. As long as a WLC is available on the network and the LAP is configured with the address of the WLC, the LAP will be able to connect to the WLC. DHCP option 43 can be used to automatically configure a LAP with the IP address of one or more WLCs, even if those WLCs reside on a different IP subnet.
A LAP requires a WLC in order to function. If the WLC becomes unavailable, the LAP will reboot and drop all client associations until the WLC becomes available or until another WLC is found on the network.
The WLC, not the LAP, determines which radio frequency (RF) channel should be used to transmit 802.11 frames in LWAPP operations. The WLC is responsible for selecting the RF channel to use, determining the output power for each LAP, authenticating users, managing security policies, and determining the least used LAP to associate with clients.
Reference:
Cisco: Lightweight AP (LAP) Registration to a Wireless LAN Controller (WLC): Background Information Cisco: Lightweight Access Point FAQ
Cisco: Wireless LAN Controller and Lightweight Access Point Basic Configuration Example: Configure the Switch for the APs
NEW QUESTION NO: 11
Which of the following network issues can most likely be mitigated by using a modular architecture?
(Choose three.)
A. hardware failures
B. physical link failures
C. application failures
D. poor scalability
E. poor redundancy
Answer: A,B,D
Explanation/Reference:
Section: Design Objectives Explanation
Explanation:
Most likely, hardware failures, physical link failures, and poor scalability can be mitigated by using a modular architecture. The modularity and hierarchy principles are complementary components of network architecture. The modularity principle is used to implement an amount of isolation among network components. This ensures that changes to any given component have little to no effect on the rest of the network. Thus hardware failures and physical link failures, which are detrimental to network stability and reliability, are less likely to cause system-wide issues. Modularity facilitates scalability because it allows changes or growth to occur without system-wide outages.
The hierarchy principle is the structured manner in which both the physical functions and the logical functions of the network are arranged. A typical hierarchical network consists of three layers: the core layer, the distribution layer, and the access layer. The modules between these layers are connected to each other in a fashion that facilitates high availability. However, each layer is responsible for specific network functions that are independent from the other layers.
The core layer provides fast transport services between buildings and the data center. The distribution layer provides link aggregation between layers. Because the distribution layer is the intermediary between the access layer and the campus core layer, the distribution layer is the ideal place to enforce security policies, provide load balancing, provide Quality of Service (QoS), and perform tasks that involve packet manipulation, such as routing. The access layer, which typically comprises Open Systems Interconnection (OSI) Layer 2 switches, serves as a media termination point for devices, such as servers and workstations.
Because access layer devices provide access to the network, the access layer is the ideal place to perform user authentication and to institute port security. High availability, broadcast suppression, and rate limiting are also characteristics of access layer devices.
Application failures and poor redundancy are less likely to be mitigated by using a modular architecture.
Poor redundancy and resiliency are more likely to be mitigated by a full-mesh topology. However, full-mesh topologies restrict scalability. Application failures can be mitigated by server redundancy.
Reference:
Cisco: Enterprise Campus 3.0 Architecture: Overview and Framework: ModularityCategory: Design Objectives
NEW QUESTION NO: 12
Which of the following are not true of the access layer of a hierarchical design? (Choose three.)
A. It provides address summarization.
B. It aggregates LAN wiring closets.
C. It isolates the distribution and core layers.
D. It performs Layer 2 switching.
E. It performs NAC for end users.
Answer: A,B,C
Explanation/Reference:
Section: Enterprise Network Design Explanation
Explanation:
The access layer typically performs Open Systems Interconnection (OSI) Layer 2 switching and Network Admission Control (NAC) for end users. The access layer is the network hierarchical layer where end-user devices connect to the network. Port security and Spanning Tree Protocol (STP) toolkit features like PortFast are typically implemented in the access layer.
The distribution layer of a hierarchical design, not the access layer, provides address summarization, aggregates LAN wiring closets, and aggregates WAN connections. The distribution layer is used to connect the devices at the access layer to those in the core layer. Therefore, the distribution layer isolates the access layer from the core layer. In addition to these features, the distribution layer can also be used to provide policy-based routing, security filtering, redundancy, load balancing, Quality of Service (QoS), virtual LAN (VLAN) segregation of departments, inter-VLAN routing, translation between types of network media, routing protocol redistribution, and more.
The core layer of a hierarchical design, not the access layer, is also known as the backbone layer. The core layer is used to provide connectivity to devices connected through the distribution layer. In addition, it is the layer that is typically connected to enterprise edge modules. Cisco recommends that the core layer provide fast transport, high reliability, redundancy, fault tolerance, low latency, limited diameter, and QoS.
However, the core layer should not include features that could inhibit CPU performance. For example, packet manipulation that results from some security, QoS, classification, or inspection features can be a drain on resources.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 2, Access Layer, pp. 44-46
Cisco: High Availability Campus Network DesignRouted Access Layer using EIGRP or OSPF: Hierarchical Design
NEW QUESTION NO: 13
Which of the following methods is always used by a new LAP to discover a WLC?
A. broadcast
B. OTAP
C. DHCP
D. DNS
E. NVRAM
Answer: C
Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
When you add a lightweight access point (LAP) to a wireless network that uses Lightweight Access Point Protocol (LWAPP), the LAP goes through a sequence of steps to discover and register with a wireless LAN controller (WLC) on the network. Because a new LAP has not been configured with a static IP address, the LAP will first attempt to obtain an address from a Dynamic Host Configuration Protocol (DHCP) server.
When the LAP receives an IP address, the LAP scans the DHCP server response for option 43, which identifies the address of a WLC. Although this method is always the first action taken by a new LAP when it attempts to discover a WLC, the LAP will also use other methods.
When the LAP receives an IP address from the DHCP server, the LAP can also receive other configuration parameters, such as the IP address of a Domain Name System (DNS) server. If a DNS server is configured, the LAP will attempt to resolve the host name CISCO-LWAPP-CONTROLLER.localdomain, where localdomain is the fully qualified domain name (FQDN) in use. Once the LAP has resolved the name to one or more IP addresses, the LAP will send an LWAPP discovery message to all of the IP addresses simultaneously.
Alternatively, a LAP can use Over-the-Air-Provisioning (OTAP) to discover a WLC. OTAP is enabled by default on a new LAP. With OTAP, LAPs periodically transmit neighbor messages that contain the IP address of a WLC. A new LAP that has OTAP enabled can scan the wireless network for neighbor messages until the LAP locates the IP address of a local WLC. Once the LAP has discovered the IP address of a WLC, the LAP will send a Layer 3 LWAPP discovery request directly to the WLC.
If Layer 2 LWAPP mode is supported, a new LAP can attempt to locate a WLC by broadcasting a Layer 2 LWAPP discovery request message. If there are no WLCs on that network segment or if a WLC does not respond to the Layer 2 broadcast, the LAP will then broadcast a Layer 3 LWAPP discovery request message.
A new LAP will not have the address of a WLC stored in nonvolatile random access memory (NVRAM) by default. However, you can configure a LAP with the IP address of a WLC to facilitate the discovery of a WLC when the LAP is installed. In addition, if a LAP has ever joined with a WLC, it may store the previously discovered WLC IP address as a primary, secondary, or tertiary WLC.
Reference:
Cisco: Lightweight AP (LAP) Registration to a Wireless LAN Controller (WLC): Register the LAP with the WLC
NEW QUESTION NO: 14
At which of the following layers of the OSI model does CDP operate?A. Application layer
B. Transport layer
C. Network Layer
D. Data Link layer
E. Physical Layer
Answer: D
Explanation/Reference:
Section: Design Methodologies Explanation
Explanation:
Cisco Discovery Protocol (CDP) operates at the Data Link layer, or Layer 2, of the Open Systems Interconnection (OSI) model. CDP is a proprietary protocol used by Cisco devices to detect neighboring Cisco devices. For example, Cisco switches use CDP to determine whether a directly connected Voice over IP (VoIP) phone is manufactured by Cisco or by a third party. CDP packets are broadcast from a CDP-enabled device to a multicast address. Each directly connected CDP-enabled device receives the broadcast and uses that information to build a CDP table. The CDP table contains a significant amount of information, including the following:
The device ID of the neighboring device
The capabilities of the neighboring device
The product number of the neighboring device
The holdtime
The local interface
The remote interface
Although CDP does not operate at the Physical layer, or Layer 1, it relies on a fully operational Physical layer. CDP packets are encapsulated by the CDP process on a Cisco device and then passed to the Physical layer for transmission onto the Physical medium, typically as electrical or optimal pulses which represent the bits of data. If CDP information is not being exchanged between directly connected devices, you should first check for Physical layer connectivity issues before moving on to troubleshoot potential Data Link layer connectivity issues.
CDP does not operate at any OSI layer above the Data Link layer, such as the Network layer (Layer 3), Transport layer (Layer 4), or Application layer (Layer 7). One of the strengths of CDP is that its operation is network protocol agnostic? meaning that CDP is not dependent on any particular Network layer protocol addressing scheme, such as IP addressing. For example, two directly connected devices with misconfigured IP addressing can still communicate and share information.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 15, CDP, p. 629
Cisco: Configuring Cisco Discovery Protocol
NEW QUESTION NO: 15
Which of the following is the QoS model that is primarily used on the Internet?
A. best-effort
B. IntServ
C. DiffServ
D. AutoQoS
Answer: A
Explanation/Reference:
Section: Enterprise Network Design Explanation
Explanation:
The best-effort model is the Quality of Service (QoS) model that is primarily used on the Internet. No QoS mechanisms are used when the best-effort model is implemented; all packets are treated with equal priority. The best-effort model is very scalable and easy to implement. However, since bandwidth is not guaranteed for any packet types the best-effort model can be a key limitation when considering an Internet circuit as a backup connection for an enterprise wide area network (WAN).
The Integrated Services (IntServ) model is not the QoS model primarily used on the Internet. IntServ, which was the first QoS model, provides end-to-end reliability guarantees for bandwidth, delay, and packet loss. However, IntServ is not very scalable, since its signaling overhead can consume a lot of bandwidth.
IntServ uses Resource Reservation Protocol (RSVP) as the signaling protocol.
The Differentiated Services (DiffServ) model is also not the QoS model primarily used on the Internet.
DiffServ does not provide end-to-end reliability guarantees. Instead, it provides per-hop QoS mechanisms.
Because end-to-end signaling is not required, bandwidth is not consumed by signaling overhead?
therefore, DiffServ is more scalable than IntServ. However, the QoS mechanisms employed by DiffServ must be configured consistently at each hop.
AutoQoS is not a QoS model. AutoQoS automates the configuration of QoS on Cisco devices, enabling consistent configurations throughout a large network.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 7, WAN Backup over the Internet, pp. 263-264 Cisco: QoS Fact or Fiction
NEW QUESTION NO: 16
Which of the following can you use to hide the IP addresses of hosts on an internal network when transmitting packets to an external network, such as the Internet?
A. a DMZ
B. WPA
C. an ACL
D. NAT
Answer: D
Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
You can use Network Address Translation (NAT) to hide the IP addresses of hosts on an internal network when transmitting packets to an external network, such as the Internet. NAT is used to translate private IP addresses to public IP addresses. Private-to-public address translation enables hosts on a privately addressed internal network to communicate with hosts on a public network, such as the Internet. Typically, internal networks use private IP addresses, which are not globally routable. In order to enable communication with hosts on the Internet, which use public IP addresses, NAT translates the private IP addresses to a public IP address. Port Address Translation (PAT) can further refine what type of communication is allowed between an externally facing resource and an internally facing resource by designating the port numbers to be used during communication. PAT can create multiple unique connections between the same external and internal resources.
You cannot use a demilitarized zone (DMZ) to hide the IP addresses of hosts on an internal network when transmitting packets to an external network. A DMZ is a network segment that is used as a boundary between an internal network and an external network, such as the Internet. A DMZ network segment is typically used with an access control method to permit external users to access specific externally facing servers, such as web servers and proxy servers, without providing access to the rest of the internal network. This helps limit the attack surface of a network.
You cannot use Wi-Fi Protected Access (WPA) to hide the IP addresses of hosts on an internal network when transmitting packets to an external network. WPA is a wireless standard that is used to encrypt data transmitted over a wireless network. WPA was designed to address weaknesses in Wired Equivalent Privacy (WEP) by using a more advanced encryption method called Temporal Key Integrity Protocol (TKIP). TKIP provides 128bit encryption, key hashing, and message integrity checks. TKIP can be configured to change keys dynamically, which increases wireless network security.
You cannot use an access control list (ACL) to hide the IP addresses of hosts on an internal network when transmitting packets to an external network. ACLs are used to control packet flow across a network. They can either permit or deny packets based on source network, destination network, protocol, or destination port. Each ACL can only be applied to a single protocol per interface and per direction. Multiple ACLs can be used to accomplish more complex packet flow throughout an organization. For example, you could use an ACL on a router to restrict a specific type of traffic, such as Telnet sessions, from passing through a corporate network.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 8, NAT, pp. 300-302
NEW QUESTION NO: 17
STP is disabled by default in which of the following Layer 2 access designs?
A. Flex Link
B. loop-free U
C. looped triangle
D. loop-free inverted U
E. looped square
Answer: A
Explanation/Reference:
Section: Enterprise Network Design Explanation
Explanation:
Spanning Tree Protocol (STP) is disabled by default in Flex Link designs. STP prevents switching loops on a network. Switching loops can occur when there is more than one switched path to a destination. The spanning tree algorithm determines the best path through a switched network, and any ports that create redundant paths are blocked. If the best path becomes unavailable, the network topology is recalculated and the port connected to the next best path is unblocked. There are no loops in a Flex Link design, and STP is disabled when a device is configured to participate in a Flex Link. Interface uplinks in this topology are configured in active/standby pairs, and each device can only belong to a single Flex Link pair. In the event of an uplink failure, the standby link becomes active and takes over, thereby offering redundancy when an access layer uplink fails. Possible disadvantages of the Flex Link design include its inability to return to the original state after a failed link is recovered, its increased convergence time over other designs, and its inability to run STP in order to block redundant paths that might be created by inadvertent errors in cabling or configuration.
STP is not disabled by default in loop-free inverted U designs. Loop-free inverted U designs offer redundancy at the aggregation layer, not the access layer? therefore, traffic will black-hole upon failure of an access switch uplink. All uplinks are active with no looping, thus there is no STP blocking by default.
However, STP is still essential so that redundant paths that might be created by any inadvertent errors in cabling or configuration are blocked.
STP is not disabled by default in loop-free U designs. This topology offers a redundant link between access layer switches as well as a redundant link at the aggregation layer. Because of the redundant path in both layers, extending a virtual LAN (VLAN) beyond an individual access layer pair would create a loop?
therefore, loop-free U designs cannot support VLAN extensions. Like loop-free inverted U designs, loop- free U designs also run STP and have issues with traffic being black-holed upon failure of an access switch uplink.
STP is not disabled by default in looped triangle designs. A looped triangle design can provide deterministic convergence in the event of a link failure. In a triangle design, each access layer device has direct paths to redundant aggregation layer devices. The ability to recover from a failed link in this design is granted by redundant physical connections that are blocked by Rapid STP (RSTP) until the primary connection fails. RSTP is an evolution of STP that provides faster convergence. RSTP achieves this by merging the disabled, blocking, and listening states into a single state, called the discarding port state.
With fewer port states to transition through, convergence is faster. A looped triangle topology is currently the most common design in enterprise data centers.
STP is not disabled by default in looped square designs. Like a looped triangle, a looped square design can provide deterministic convergence through redundant connections. However, the difference between the two is that in a looped square the redundant link exists between the access layer devices themselves, whereas in a looped triangle the redundant link exists between the access layer devices and the aggregation layer devices. In a looped square, the connection between the access layer devices is blocked by STP until a primary link failure occurs.
Reference:
Cisco: Data Center Access Layer Design: FlexLinks Access Model
NEW QUESTION NO: 18
Which of the following statements is not true?
A. The access layer should not contain physically connected hosts.
B. The access layer provides NAC.
C. The core layer should provide fast convergence.
D. The core layer should provide high resiliency.
E. The distribution layer provides inter-VLAN routing.
F. The distribution layer provides route filtering.
Answer: A
Explanation/Reference:
Section: Enterprise Network Design Explanation
Explanation:
The access layer should contain physically connected hosts because it is the tier at which end users connect to the network. The access layer serves as a media termination point for endpoints such as servers and hosts. Because access layer devices provide access to the network, the access layer is the ideal place to perform user authentication.
The hierarchical model divides the network into three distinct components:
Core layer
Distribution layer
Access layer
The access layer provides Network Admission Control (NAC). NAC is a Cisco feature that prevents hosts from accessing the network if they do not comply with organizational requirements, such as having an updated antivirus definition file. NAC Profiler automates NAC by automatically discovering and inventorying devices attached to the LAN.
The core layer of the hierarchical model is primarily associated with low latency and high reliability. It is the only layer of the model that should not contain physically connected hosts. As the network backbone, the core layer provides fast convergence and typically provides the fastest switching path in the network. The functionality of the core layer can be collapsed into the distribution layer if the distribution layer infrastructure is sufficient to meet the design requirements. Thus the core layer does not contain physically connected hosts. For example, in a small enterprise campus implementation, a distinct core layer may not be required, because the network services normally provided by the core layer are provided by a collapsed core layer instead.
The distribution layer provides route filtering and inter-VLAN routing. The distribution layer serves as an aggregation point for access layer network links. In addition, the distribution layer can contain connections to physical hosts. Because the distribution layer is the intermediary between the access layer and the core layer, the distribution layer is the ideal place to enforce security policies, to provide Quality of Service (QoS), and to perform tasks that involve packet manipulation, such as routing. Summarization and next- hop redundancy are also performed in the distribution layer.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 2, Access Layer, pp. 44-46
Cisco: Campus Network for High Availability Design Guide: Access Layer
NEW QUESTION NO: 19
Which of the following WLC interfaces is used for Layer 2 discovery?
A. the management interface
B. the service port interface
C. the AP manager interface
D. the dynamic interface
E. the virtual interface
Answer: A
Explanation/Reference:
Section: Considerations for Expanding an Existing Network Explanation
Explanation:
The management interface on a Cisco wireless LAN controller (WLC) is used for Layer 2 discovery. A WLC interface is a logical interface that can be mapped to at least one physical port. The port mapping is typically implemented as a virtual LAN (VLAN) on an 802.1Q trunk. A WLC has five interface types:
Management interface
Service port interface
Access point (AP) manager interface
Dynamic interface
Virtual interface
The management interface is used for in-band management, for Layer 2 discovery operations, and for enterprise services such as authentication, authorization, and accounting (AAA). The service port interface is statically mapped to the service port on the WLC and is used for out-of-band management. The AP manager interface is used for Layer 3 discovery operations and handles all Layer 3 communications between the WLC and an associated AP.
The virtual interface is a special interface used to support wireless client mobility. The virtual interface acts as a Dynamic Host Configuration Protocol (DHCP) server placeholder and supports DHCP relay functionality. In addition, the virtual interface is used to implement Layer 3 security, such as redirects for a web authentication login page.
The dynamic interface type is used to map VLANs on the WLC for wireless client data transfer. A WLC can support up to 512 dynamic interfaces mapped onto an 802.1Q trunk on a physical port or onto multiple ports configured as a single port group using link aggregation (LAG).
Reference:
CCDA 200-310 Official Cert Guide, Chapter 4, WLC Interface Types, pp. 184-185 Cisco: Cisco Wireless LAN Controller Configuration Guide, Release 7.4: Information About Interfaces
NEW QUESTION NO: 20
Which of the following is a circuit-switched WAN technology that offers less than 2 Mbps of bandwidth?
A. ATM
B. Frame Relay
C. ISDN
D. SONET
E. SMDS
F. Metro Ethernet
Answer: C
Explanation/Reference:
Section: Enterprise Network Design Explanation
Explanation:
Integrated Services Digital Network (ISDN) is a circuit-switched WAN technology that offers less than 2 Mbps of bandwidth. Circuit-switched WAN technologies rely on dedicated physical paths between nodes in a network. For example, when RouterA needs to contact RouterB, a dedicated path is established between the routers and then data is transmitted. While the circuit is established, RouterA cannot use the WAN link to transmit any data that is not destined for networks accessible through RouterB. When RouterA no longer has data for RouterB, the circuit is torn down until it is needed again.
Because circuit-switched links rely on dedicated physical paths, they are considered leased WAN technologies. Other examples of leased WAN technologies are time division multiplexing (TDM) and Synchronous Optical Network (SONET).
Metro Ethernet is a WAN technology that is commonly used to connect networks in the same metropolitan area. However, Metro Ethernet providers typically provide up to 1,000 Mbps of bandwidth. A company that has multiple branch offices within the same city can use Metro Ethernet to connect the branch offices to the corporate headquarters.
Packet-switched networks do not rely on dedicated physical paths between nodes in a network. In a packet-switched network, a node establishes a single physical circuit to a service provider. Multiple virtual circuits can share this physical circuit, allowing a single device to send data to several destinations.
Because packet-switched links do not rely on dedicated physical paths, they are considered shared WAN links. Frame Relay, X.25, Multiprotocol Label Switching (MPLS), and Switched Multimegabit Data Service (SMDS) are examples of packet-switched, shared WAN technologies.
Asynchronous Transfer Mode (ATM) is a shared WAN technology that transports its payload in a series of fixed-sized 53byte cells. ATM has the unique ability to transport different types of traffic, including IP packets, traditional circuit-switched voice, and video, while still maintaining a high quality of service for delay-sensitive traffic such as voice and video services. Although ATM could be categorized as a packet- switched WAN technology, it is often listed in its own category as a cell-switched WAN technology instead.
Reference:
CCDA 200-310 Official Cert Guide, Chapter 6, ISDN, pp. 221-222
Cisco: Introduction to WAN Technologies: Circuit Switching
Cisco: Asynchronous Transfer Mode Switching: ATM Devices and the Network Environment
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