CCNA Exam 640-802 (Part 1) Practice Test

A key function of the transport layer is to provide connection services for the protocols and applications that run at the levels above it. These can be categorized as either connection-oriented services or connectionless services. Some protocol suites, such as TCP/IP, provide both a connection-oriented and a connectionless transport layer protocol, to suit the needs of different applications. The transport layer is also the place in the layer stack where functions are normally included to add features to end-to-end data transport. Where network layer protocols are normally concerned with just "best effort" communications, where delivery is not guaranteed. Transport layer protocols are given intelligence in the form of algorithms that ensure that reliable and efficient communication between devices takes place. This encompasses several related jobs, including lost transmission detection and handling, and managing the rate at which data is sent to ensure that the receiving device is not overwhelmed. Transmission quality, meaning ensuring that transmissions are received as sent, is so important that some networking references define the transport layer on the basis of reliability and flow-control functions. However, not all transport layer protocols provide these services. Just as a protocol suite may have a connection-oriented and a connectionless transport layer protocol, it may also have one that provides reliability and data management services, and one that does not. Again, this is the case with TCP/IP: there is one main transport layer protocol; TCP, that includes reliability and flow control features, and a second, UDP, that doesn't.

Layer 4 of the OSI model is responsible for the functions of acknowledgements, sequencing, and flow control. This layer is known as the Transport Layer. It ensures that data is delivered reliably and in the correct order by providing error detection and correction, as well as managing the flow of data between the source and destination.

Current Ethernet technololgy typically comes via either copper UTP or fiber ccables. In this scenario the distance between the buildings is only 55 meters so either copper or fiber could be used, as the distance limitation for 100M UTP Ethernet is 100 meters. However, fiber would be a better fit as it is not prone to errors that could occur due to the voltage potential differences. Because fiber is a dielectric material, it's not susceptible to electrical interference. FO-product vendors also claim that fiber systems make secure communications easier. Interference immunity and lack of emissions are givens in FO systems and in the fiber medium itself.

HTTPS is the secured version of the HTTP application, which normally uses 128 bit SSL encryption to secure the information sent and received on a web page. An example is a banking web site, or a trustworthy shopping web site that takes credit card information. It is an application layer protocol which uses TCP port 443. Incorrect Answers: A. HTML is not a protocol. C. TFTP uses UDP port 69. D. Telnet uses TCP port 23. E. SMTP uses TCP port 25.

The application layer is the highest layer (layer 7) of the OSI model, and is reserved for end user applications. Since FTP is itself an application, layer 7 is the highest layer used. Incorrect Answers: B, C, D, E, F, G. In any given FTP session, all of these layers will be used at some point but they are incorrect because the question asked for the highest layer used by FTP.

Switches increase the number of collision domains in the network. This means that each port on a switch is its own collision domain, whereas with hubs, all ports are in the same collision domain. By dividing the network into multiple collision domains, switches can reduce the chances of collisions occurring and improve network performance.

The Transport layer (Layer 4) defines several functions, including the choice of protocols. The most important Layer 4 functions are error recovery and flow control. The transport layer may provide for retransmission, i.e., error recovery, and may use flow control to prevent unnecessary congestion by attempting to send data at a rate that the network can accommodate, or it might not, depending on the choice of protocols. Multiplexing of incoming data for different flows to applications on the same host is also performed. Reordering of the incoming data stream when packets arrive out of order is included. Examples include: TCP, UDP, and SPX.

IP Addressing and IP routing resides on the OSI Network layer, which is layer 3.

The Transport layer can provide reliable networking via acknowledgments, sequencing, and flow control. Acknowledgments Delivered segments are acknowledged to the sender. If they are not acknowledged, the sender will retransmit. Sequencing Data segments are sequenced into their original order when they arrive at the destination. Flow Control Provides buffer controls that prevent packet flooding to the destination host. Buffers store bursts of data for processing when the transmission is complete. Layer 4 protocols include the following: Transmission Control Protocol (TCP) User Datagram Protocol (UDP) Sequenced Packet Exchange (SPX)A reliable communications protocol created by Novell NetWare

Layer 7 is the application layer, which is the highest layer in the OSI model. This layer describes the use of end user applications, such as opening movie files (avi, mpeg, etc) used Microsoft Office applications, using WWW browsers, using Telnet, and using FTP.

TCP/IP includes ICMP, a protocol designed to help manage and control the operation of a TCP/IP network. The ICMP protocol provides a wide variety of information about a network's health and operational status. Control message is the most descriptive part of a name. ICMP helps control and manage IP's work and therefore is considered part of TCP/IP's network layer. CCNA Self-Study CCNA ICND exam certification Guide (Cisco Press, ISBN 1-58720-083-X) page 277.

TCP is a reliable connection-oriented protocol. TCP uses acknowledgments, sequencing, and flow control to ensure reliability. Telnet uses TCP port 23.

The correct answer is Network because the Network layer header contains the address of a destination host that is on another network. This layer is responsible for routing and addressing packets, ensuring that they are delivered to the correct destination across different networks. The Network layer header includes the source and destination IP addresses, which are used to determine the path the packet should take to reach its destination.

Every network looks for cost efficiency. Redundancy is often sacrificed on the altar of monthly cost. Thus, the hub and spoke Frame Relay network design is one of the more common. In this configuration, you pick a centralized location (most likely, your largest, most connected office) as the "hub" of the network. All other locations are considered "spokes" and have a single virtual circuit connection back to the hub. The major advantage of this configuration is the cost. It offers the cheapest monthly price tag, which cost-cutting corporations enjoy. The disadvantages are beginning to mount against this design, however. The redundancy is sorely lacking. If a single router (the central router) loses connectivity for any reason (if the router crashes, if a trenching company cuts through the line), your entire WAN goes down. The other disadvantage of this design is beginning to eclipse even redundancy. It is the disadvantage of tandem switching. Any time the spoke offices need to reach each other, they must go through the hub office.

TCP (Transmission Control Protocol) is a reliable mechanism for data delivery. SMTP, FTP and HTTP services use TCP via ports 25, 20/21, and 80, respectively.

The best network device to directly connect the phones and computers is a switch. A switch allows for the creation of virtual LANs (VLANs) which can separate the phone traffic from the office computer data traffic. By implementing VLANs on the switch, the company can ensure that the phone data sessions have maximum throughput without interfering with the office computer data traffic.

The primary functions of a router are: Packet Switching and Path Selection. It is the routers job to determine the best method for delivering the data, and switching that data as quickly as possible.

The application layer is the top layer of the OSI model and is used to describe the end user applications that can be used over a network. Layer Name Examples Application (layer 7) Telnet, HTTP, FTP, WWW browsers, NFS, SMTP gateways, SNMP
Incorrect Answers: A. TCP resides at layer 4. D. ARP is a function of the data link layer, which is layer 2. E. IP is used at layer 3 (network layer). Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press, ISBN 1-58720-094-5) Page 34.

A TCP window the amount of outstanding (unacknowledged by the recipient) data a sender can send on a particular connection before it gets an acknowledgment back from the receiver that it has gotten some of it. For example if a pair of hosts are talking over a TCP connection that has a TCP window size of 64 KB (kilobytes), the sender can only send 64 KB of data and then it must stop and wait for an acknowledgment from the receiver that some or all of the data has been received. If the receiver acknowledges that all the data has been received then the sender is free to send another 64 KB. One way to improve the reliability of the TCP connection is to reduce the window size that the receiver needs to receive before sending an acknowledgement. However, this will reduce throughput as more segments and acknowledgements will need to be sent in order to transfer the same amount of data.

Switches increases the number of collisions domains in the network. Switches that are configured with VLANs will reduce the size of the collision domains by increasing the number of collision domains in a network, but making them smaller than that of one big, flat network.

The following port numbers for the protocols listed above are as follows:
FTP: TCP Port 20 and 21 SMTP: TCP Port 25 Telnet: TCP Port 23 DNS: both TCP and UDP Port 53

A: A half duplex connection is where only one device can send or receive at a time. A full duplex connection is where both devices can send and receive at the same time. Thus, if you have a 100Mb half-duplex connection, only sending at 100Mb OR receiving at 100Mb can happen at the same time. If you have a 100Mb full duplex connection, you can effectively get 200Mb out of the link because you could be sending 100Mb and receiving 100Mb at the same time. D: Switches are capable of filtering frames based on any Layer 2 fields. For example, a switch can be programmed to reject (not forward) all frames sourced from a particular network. Because link layer information often includes a reference to an upper-layer protocol, switches usually can filter on this parameter. Furthermore, filters can be helpful in dealing with unnecessary broadcast and multicast packets.

The exhibit shown above is describing a data structure called a TCP segment. TCP (Transmission Control Protocol) is a protocol used for reliable and ordered delivery of data over a network. A TCP segment is a unit of data that is encapsulated within an IP datagram and transmitted over an Ethernet frame or other network protocols. It contains information such as source and destination port numbers, sequence and acknowledgment numbers, and control flags. Therefore, the correct answer is TCP segment.

A logical path is created between two host systems at the Network layer of the OSI model. This layer is responsible for routing and addressing, ensuring that data packets are correctly delivered from the source to the destination. Therefore, the logical path between host systems CK1 and CK2 on the Certkiller LAN would be established at the Network layer.

The OSI (Open System Interconnection) reference model was created as a reference point for communications devices. A layered approach is used to segment the entire telecommunications process into a series of smaller steps. A is correct because it encourages a level of standardization by encouraging that functions be compared to known layers. D is also correct because it allows engineers to focus on the development, refining, and perfection of simpler components.

Since the email server resides on a different IP subnet than the host Certkiller 1, the host will send the frame to its default gateway. In this case, the router Certkiller C is acting as the default gateway for all hosts on the LAN, so the frame will be sent to its Ethernet interface so that it can be routed to the email server.

You can think of the partial mesh Frame Relay design as the compromise between network administrators and cost-saving managers.

A CSU/DSU terminates a digital local loop. This means that it connects the customer's equipment to the service provider's network by converting the digital signals from the customer's equipment into a format that can be transmitted over the digital local loop.

A modem terminates an analog local loop. This means that it connects the customer's equipment to the service provider's network by converting the analog signals from the customer's equipment into a format that can be transmitted over the analog local loop.

A router is commonly considered a DTE device. DTE stands for Data Terminal Equipment, and a router is a device that connects multiple networks together and directs traffic between them. It is commonly considered a DTE device because it is the endpoint of a communication circuit.

In summary, a CSU/DSU terminates a digital local loop, a modem terminates an analog local loop, and a router is commonly considered a DTE device.

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When packets transfer from one host to another across a routed segment, the source IP address always remains the same source IP address, and the physical (MAC) address will be the existing router's interface address. Similarly, the destination IP address always remains the same and the destination physical (MAC) address is the destination router's interface address.

Switches usually have a higher number of ports than most bridges because switches are designed to connect multiple devices within a LAN, so they need to support more connections. Both bridges and switches forward Layer 2 broadcasts because they operate at the data link layer of the OSI model, which includes the handling of broadcast traffic. Both bridges and switches make forwarding decisions based on Layer 2 addresses because they use MAC addresses to determine where to forward data packets within the network.

In order to successfully configure a static NAT translation, the interfaces must be configured for NAT, in addition to the global NAT command that was entered. The router interface that lies on the inside part of the network must be defined using the "ip nat inside" command. Similarly, the WAN interface that is being used for the Internet connection must be defined using the "ip nat outside" command. Incorrect Answers: A. In order to make an internal server reachable from the Internet, a static one to one NAT entry must be configured for the server. The keyword "overload" is used to configure many to one NAT, or PAT. B, C. This need not be done in order to create a static NAT entry. These steps are typically done in setting up NAT so that inside LAN users can access the Internet via NAT.

SMTP (Simple Mail Transfer Profile for email), FTP (File Transfer Protocol), and HTTP/HTTPS (Hyper Text Transfer Protocol for internet) all use TCP because of the reliable delivery mechanism. SMTP uses TCP port 25, FTP uses TCP ports 20 and 21, HTTP uses TCP port 80, and HTTPS uses TCP port 443. Incorrect Answers: A, C: SNMP and TFTP use UDP as the transport mechanism. Generally speaking, protocols that use the keywords "trivial" or "simple" uses UDP, since connectionless, best effort delivery mechanism usually suffice. Reference: CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press, ISBN 1-58720-094-5) Page 163.

This can perform the trace command. It sends the ping packets to each of the routers on the way to the receiver. The router which doesn't respond will be a potential failure place in this network.

Required Number of hosts :50 When We use the 26 bits for Network : 11111111.11111111.11111111.11000000 so 62 usable host can be in one network. 50 host for now and remaining hosts address for further growth. Network 2 Required Number of Hosts: 20
When we use the 27 bits for Network: 11111111.11111111.1111111.11100000 so 30 usable hosts can be in one network. Network 3 Required Number of Hosts: 10
When we use the 28 bits for Network: 11111111.11111111.11111111.11110000 so 14 usable hosts can be in one network. Connection between CK1 , CK2 and CK3 is WAN so when you use 30 bits network IP, you will not lose any IP addresses from network since this subnet allows for only 2 host addresses.

When packets leave from the host, the packets contains the source MAC and IP of the host address. The source and destination IP address will not change. Because the host knows that the destination is on another subnet, it will forward the packet to the default gateway device, so the destination MAC address will be of the default gateway, which is the FA0/0 interface of router Certkiller 3.

If the destination host is in the remote segment than the router will change the MAC address of the source to its own. The inverse ARP protocol is by default on. Remember that IP address is not changed after forwarding. The MAC address is changed after crossing each broadcast domain.

A hub simply repeats the electrical signal and makes no attempt to interpret the electrical signal (layer 1) as a LAN frame (Layer 2). So, a hub actually performs OSI layer 1 functions, repeating an electrical signal, whereas a switch performs OSI layer 2 functions, actually interpreting Ethernet header information, particularly addresses, to make forwarding decisions. Hubs can be used to increase the number of stations that can be supported on a LAN. Because the repeater does not interpret what the bits mean, but does examine and generate electrical signals, a repeater is considered to operate at Layer 1. Repeaters can be used to physically extend the LAN to greater distances.

CDP (Cisco Discovery Protocol) is a Cisco proprietary protocol used to gather information about directly connected Cisco devices. By using CDP, the Certkiller network administrator can obtain the IP Address of a connected device in order to telnet to it, allowing for remote management and configuration. Additionally, CDP can be used to verify Layer 2 connectivity between two devices when Layer 3 fails, helping to troubleshoot and diagnose network connectivity issues.

Since private network use RFC 1918 IP address ranges internally, and because of security reasons, it is generally not possible to use an interior routing protocol with the ISP. This eliminates choice B. When connecting to an ISP, usually only BGP or static routes are supported. In this case, since there is only one connection to the Internet, BGP is not needed so choices A and D can be eliminated. A static default route would be needed on router CK1 to route to the Internet. In turn, the ISP only needs a specific static route to reach the LAN of the Certkiller network. Incorrect Answers: A, D: BGP is not needed on networks that contain only a single link to the Internet. B. Interior routing protocols are generally not supported with an ISP. C. A default route on the ISP router would send all of their customers Internet traffic to the Certkiller network, and not the Internet.

A WAN is a data communications network that covers a relatively broad geographic area and that often uses transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower two layers of the OSI reference model: the physical layer and the data link layer as shown below.
Note: Occasionally WAN's would also be considered to operate at layer 3, but since this question asked for only 2 chopices layers 1 and 2 are better choices.

When packets leave from the host, the packets contains the source MAC and IP of the host address. The source and destination IP address will not change (if it did, the router devices would not know where to send the data). Because the host knows that the destination is on another subnet, it will forward the packet to the default gateway device, so the destination MAC address will be of the default gateway, which is the LAN interface of router Certkiller 1.

CDP (Cisco Discovery Protocol) is a Cisco proprietary protocol that runs between Cisco devices. It is used to discover and gather information about directly connected Cisco devices. The information supplied by CDP includes device identifiers, which are unique identifiers assigned to each Cisco device, capabilities list, which describes the features and functions supported by the device, and platform, which refers to the hardware or software platform on which the device is running. CDP does not supply route identifiers or neighbor traffic data.

Routers are Layers 3 devices used for inter-network communication. In this scenario there are two different networks, so both switches need to connect to a router using straight-through cables. A straight-through cable is used to connect two different devices like, switch to router, host to switch. Since we need to insert a router for communication between the two switches, straight through cables will be used between the switches and the router.

The first statement is correct because the destination port number in a segment header for HTTP traffic is typically 80. The second statement is incorrect because the destination IP address of a packet sent from Host Certkiller to Certkiller II will be the IP address of the network interface of the Certkiller II server, not the E0 interface of Certkiller 1 router. The third statement is correct because the destination IP address of a packet sent from Host Certkiller to Certkiller II will be the IP address of the network interface of the Certkiller II server. The fourth statement is incorrect because the destination address of a frame sent from Host Certkiller to Certkiller II will be the MAC address of the E0 interface of Certkiller 2 router, not Certkiller 1 router.

There are two ways to inject a default route into a normal area. 1. If the ASBR already has the default route in its routing table, you can advertise the existing 0.0.0.0/0 into the OSPF domain with the default-information originate router configuration command. 2. If the ASBR doesn't have a default route, you can add the keyword always to the default-information originate command (default-information originate always). This command will advertise a default route into the OSPF domain, regardless of whether it has a route to 0.0.0.0. Another benefit of adding always keyword is that it can add stability to the internetwork. For example, if the ASBR is learning a default route from another routing domain such as RIP and this route is flapping, then without the always keyword, each time the route flaps, the ASBR will send a new Type 5 LSA into the OSPF domain causing some instability inside the OSPF domain. With the always keyword, the ASBR will advertise the default inside the OSPF domain always, and thus the flapping of the default route from the RIP domain will not cause any instability inside the OSPF domain. In the example shown here, only choice D is correct as the wildcard mask correctly specifies the 10.10.2.16 0.0.0.15 networks, which include all IP addresses in the 10.10.2.16-10.10.2.31 range. Reference: http://www.cisco.com/warp/public/104/21.html

A network topology that is set up so that each device is directly connected to every other device on the network. This connection method has built-in redundancy. If one link goes down, the device will transmit via another link. Example: If the partial mesh design is a compromise between the network administrators and managers, then the full mesh design implies that the network administrators won. This design is every Cisco network administrator's picture of perfection over a Frame Relay cloud. It gives every site a direct virtual circuit to every other site, as shown in Figure This design gives maximum redundancy and minimum packet latency (latency describes how long it takes a packet to reach each location).

Spanning-Tree Protocol (STP) is a Layer 2 protocol that utilizes a special-purpose algorithm to discover physical loops in a network and effect a logical loop-free topology. STP creates a loop-free tree structure consisting of leaves and branches that span the entire Layer 2 network. The actual mechanics of how bridges communicate and how the STP algorithm works will be discussed at length in the following topics. Note that the terms bridge and switch are used interchangeably when discussing STP. In addition, unless otherwise indicated, connections between switches are assumed to be trunks. STP keeps the port either in block or in forward states, when forward port disconnect then within the less then a minute blocked port comes into forward state so packets starts to go through new forward port. The Spanning Tree Protocol (STP) would identify the best path as well as alternate path to reach in proper destination. In a redundant link, if the primary link fails then the secondary links will automatically start after few minutes. If port Fa0/9 became disconnected, then the packets would be re-routed automatically using the Certkiller A- Certkiller 2- Certkiller 3 path.

As the question states that serial line is up, it means the problem is not on the Network layer. The administrator cannot see any output by issuing the show cdp neighbors command. It means that CDP is disabled and CDP is a protocol that runs over Layer2 (the data link layer) on all Cisco routers, bridges, access servers, and switches

Both bridges and switches build the bridge table by listening to incoming frames and examining the source MAC address in the frame. Switches are multiport bridges that allow you to create multiple broadcast domains. Each broadcast domain is like a distinct virtual bridge within a switch.