Network

Packet Switching

At the barest minimum, routers are like switches because they essentially switch packets between networks.

Which of the following devices allows segregation of collision domains but not broadcasting domains?

SWITCH

Application Layer

The Application Layer of the TCP/IP Model consists of various protocols that perform all the functions of the OSI model's Application, Presentation and Session layers. This includes interaction with the application, data translation and encoding, dialogue control and communication coordination between systems. The following are few of the most common Application Layer protocols used today: Telnet - Telnet is a terminal emulation protocol used to access the resourses of a remote host. A host, called the Telnet server, runs a telnet server application (or daemon in Unix terms) that receives a connection from a remote host called the Telnet client. This connection is presented to the operating system of the telnet server as though it is a terminal connection connected directly (using keyboard and mouse). It is a text-based connection and usually provides access to the command line interface of the host. Remember that the application used by the client is usually named telnet also in most operating systems. You should not confuse the telnet application with the Telnet protocol. HTTP - The Hypertext Transfer Protocol is foundation of the World Wide Web. It is used to transfer Webpages and such resources from the Web Server or HTTP server to the Web Client or the HTTP client. When you use a web browser such as Internet Explorer or Firefox, you are using a web client. It uses HTTP to transfer web pages that you request from the remote servers. FTP - File Transfer Protocol is a protocol used for transferring files between two hosts. Just like telnet and HTTP, one host runs the FTP server application (or daemon) and is called the FTP server while the FTP client runs the FTP client application. A client connecting to the FTP server may be required to authenticate before being given access to the file structure. Once authenticated, the client can view directory listings, get and send files, and perform some other file related functions. Just like telnet, the FTP client application available in most operating systems is called ftp. So the protocol and the application should not be confused. SMTP - Simple Mail Transfer Protocol is used to send e-mails. When you configure an email client to send e-mails you are using SMTP. The mail client acts as a SMTP client here. SMTP is also used between two mails servers to send and receive emails. However the end client does not receive emails using SMTP. The end clients use the POP3 protocol to do that. TFTP - Trivial File Transfer Protocol is a stripped down version of FTP. Where FTP allows a user to see a directory listing and perform some directory related functions, TFTP only allows sending and receiving of files. It is a small and fast protocol, but it does not support authentication. Because of this inherent security risk, it is not widely used. DNS - Every host in a network has a logical address called the IP address (discussed later in the chapter). These addresses are a bunch of numbers. When you go to a website such as www.cisco.com you are actually going to a host which has an IP address, but you do not have to remember the IP Address of every WebSite you visit. This is because Domain Name Service (DNS) helps map a name such as www.cisco.com to the IP address of the host where the site resides. This obviously makes it easier to find resources on a network. When you type in the address of a website in your browser, the system first sends out a DNS query to its DNS server to resolve the name to an IP address. Once the name is resolved, a HTTP session is established with the IP Address. DHCP - As you know, every host requires a logical address such as an IP address to communicate in a network. The host gets this logical address either by manual configuration or by a protocol such as Dynamic Host Configuration Protocol (DHCP). Using DHCP, a host can be provided with an IP address automatically. To understand the importance of DHCP, imagine having to manage 5000 hosts in a network and assigning them IP address manually! Apart from the IP address, a host needs other information such as the address of the DNS server it needs to contact to resolve names, gateways, subnet masks, etc. DHCP can be used to provide all these information along with the IP address.

Open Systems Interconnection (OSI)

An international standard suite of protocols defined by the International Organization for Standardization (ISO) that implements the OSI seven-layer model for network communications between computers.

collision domain

The portion of an Ethernet network in which collisions could occur if two nodes transmit data at the same time.

Wide Area Network (WAN)

This is a term used to describe a network covering a large geographical area such as a multiple cities, a country or even across the world. They are used to connect LANs across the area they cover. A typical example would be the LANs at various offices of a company connected by WAN.

Local Area Network (LAN)

This is a term used to describe a network covering a limited geographical area such as a floor, building or a campus. LAN usually has a high data-transfer rate. The Ethernet standard is the most commonly used technology in LANs. Ethernet is so common that it is almost synonymous with LAN today. As of late, wireless technology is also becoming increasingly common for a local LAN.

A technician needs to trace a wire that is in the wall. Which of the following is the BEST way for the technician to identify the wires location?

Tone Generator

Which of the following is found in a layer two switch?

VLAN settings

Which of the following cable types transmits data over 100Mbps per direction?

10GBase-T

Which of the following is the default port for POP3?

110

A network administrator is summarizing the following IP address ranges into a single route for redistribution into the network core: 192.168.0.0 /24 192.168.1.0 /24 192.168.2.0 /24 192.168.3.0 /24 Which of the following IP summary addresses will represent the listed network ranges without including any ranges not listed?

192.168.0.0/22

A Network address of 220.100.100.100 with a subnet mask of 255.255.255.0 can be rewritten in classlessinterdomain routing notation (CIDR) as which of the following?

220.100.100.100/24

When connecting two devices for voice on a vertical connect, which of the following cables would be used to connect the two devices?

25 pair cable

A user has a small network of four computers that they want to connect to a single cable modem. Which of the following devices would allow the user to do this?

4 port wireless router

TCP/IP Model

A four-layer data communication model developed by the United States Department of Defense. To some extent, it is similar to the OSI model.

switches

A layer 2 device that used to connect two or more network segments and regulate traffic.

Which of the following documentation would a network administrator need to update if they have just finished upgrading the firmware on all the switches within the LAN?

Baseline and configuration documentation

One of the routers in your company has just received information about network 172.16.10.0/24 from multiple sources. Which of the below will the router consider as the most reliable source for network 172.16.10.0/24?

CORRECT ANSWER - A directly connected interface with an IP address of 172.16.10.254/24 MORE INFORMATION: The administrative distance is used by a router to determine which routing protocol to use if two or more protocols provide routing information for the same destination network. The smaller the administrative distance is, the higher the preference. Directly connected interfaces have an AD of 0 and are always preferred. Static routes have an AD of 1, while the Enhanced Interior Gateway Routing Protocol (EIGRP) has an AD of 90, and Open Shortest Path First (OSPF) has an AD of 110.

No matter how it's configured, a single switch port is considered what?

CORRECT ANSWER - A separate collision domain MORE INFORMATION: Unlike a network hub, which is a single collision domain for all ports, each port on a Layer 2 switch is a separate collision domain.

Which of the following is not an IPv6 address type?

CORRECT ANSWER - Broadcast MORE INFORMATION: Unlike IPv4, the IP version 6 (IPv6) protocol does not use a broadcast address type. For bandwidth efficiency purposes, the duties of IPv4's broadcast addressing have been incorporated into IPv6 multicast addressing.

Which Ethernet switching method would you use if low latency is of utmost importance?

CORRECT ANSWER - Cut-through MORE INFORMATION: Cut-through provides the lowest-latency switching available. It forwards Ethernet packets faster than any other method, because it only waits to read the destination MAC address before forwarding.

Identify which of the services below uses both TCP and UDP ports.

CORRECT ANSWER - DNS MORE INFORMATION: The DNS protocol is the only protocol of those listed above that uses both the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP). UDP is the preferred transport protocol for DNS services because it is fast. UDP doesn't require a connection to be established between the hosts before sending any data. If a host fails to receive a response from a DNS server after several requests, it can then switch to TCP. TCP is slower, but more reliable, because it requires a three-way handshake to be established between the hosts before any data is sent.

Host A receives a frame and discards it after determining it is corrupt. Which OSI layer checks frames for errors?

CORRECT ANSWER - Data-link MORE INFORMATION: The data-link layer is responsible for checking each received frame for errors. Every Ethernet frame includes the frame check sequence (FCS) or cyclic redundancy check value that is calculated by the host that sent the frame. The receiving host generates its own FCS value for every frame received and then compares it with the FCS included in the frame. If the FCS values match, the frame has arrived without any error. If the FCS values don't match, then the host assumes the frame has an error or is corrupt and, therefore, discards it. More information on Ethernet frames can be found on Firewall.cx's Ethernet frame analysis page.

When configuring NAT, what is the purpose of the overload command, as used in the following example: Router(config)#ip nat inside source list 1 interface gi0/2 overload

CORRECT ANSWER - It translates many local addresses into a single global address by tracking the connection's TCP port number. MORE INFORMATION: The example configuration will use the single IP address assigned to interface gi0/2. Any internal -- local -- IP that attempts to communicate with a device on the other side of gi0/2 will be translated to this single address. The router will maintain a NAT table for this connection. This table contains the local IP address of the internal device, the single IP to which it is translated and a unique TCP port number that is used to identify packets within that particular conversation.

In the network diagram above, which path will packets take when traveling from host 192.168.50.126 to host 192.168.50.5?

CORRECT ANSWER - Packets will travel from R3 to R1 and from R3 to R2 to R1. MORE INFORMATION: We begin by identifying to which network host 192.168.50.126 belongs. IP address 192.168.50.126 is the last usable address for network 192.168.50.64/26, which means it is directly connected to Router 3. Next, we need to identify where 192.168.50.5 is located. By examining the diagram, we can see IP 192.168.50.5 is Router 1's interface that connects directly with Router 2. Finally, to understand the path packets will take, we examine the output of Router 3's routing table and discover there are two equal cost links to network 192.168.50.4/30. So, EIGRP will load-balance between both paths.

Which of the following options are used in standard access lists?

CORRECT ANSWER - Source address and wildcard mask MORE INFORMATION: Standard access lists provide a simple set of options: the source address and wildcard mask. Extended access lists offer additional options -- source address, destination address, wildcard mask, protocol and ports -- thus providing greater granularity. In both cases, it's important to remember access lists always use the wildcard mask, which is the reverse of a subnet mask.

Which of the following is the correct syntax to configure a switch port as a standard user port on VLAN 10 for data and VLAN 50 for VoIP?

CORRECT ANSWER - TechTarget-SW1(config-if)#switchport mode access TechTarget-SW1(config-if)#switchport access vlan 10 TechTarget-SW1(config-if)#switchport voice vlan 50 MORE INFORMATION: When configuring a user port for both voice and data, follow three steps. The first step is to define the port as an access port, as opposed to a trunk port. Second, configure the access virtual LAN to the VLAN ID of standard data traffic. Finally, you must configure the voice VLAN to the appropriate VLAN ID.

What would the result be when the following commands are executed on a Cisco Catalyst switch: TechTarget-SW1 (config-if)# switchport port-security TechTarget-SW1 (config-if)# switchport port-security mac-address sticky

CORRECT ANSWER - The MAC address learned dynamically is saved in the switch's running-configuration. MORE INFORMATION: When the switch port-security mac-address sticky command is used without specifying a MAC address at the end, the MAC address of the attached device is dynamically learned and placed in the running configuration of the switch.

A router with a BGP autonomous system number of 65001 is peered with another router with the same BGP AS. Which of the following is true? The ebgp multihop command must be configured to reach an established state. A BGP connection will be established, but no traffic will traverse the connection. The routers are considered eBGP neighbors. The routers are considered iBGP neighbors. A BGP establishment error will occur because of the AS conflict.

CORRECT ANSWER - The routers are considered iBGP neighbors. MORE INFORMATION: When two routers belong to the same autonomous system bearing the same AS number, they are considered internal BGP, or iBGP, neighbors. This also means the routes learned between these neighbors use the internal BGP administrative distance of 200, as opposed to the external AD of 20.

Which of the following EXEC commands will reset LLDP traffic error counters?

CORRECT ANSWER - clear lldp counters MORE INFORMATION: The correct syntax to reset Link Layer Discovery Protocol (LLDP) traffic and error counters to zero is clear lldp counters. The clear lldp table command will delete the LLDP table of any information about learned neighbors. All other answers have incorrect or incomplete syntax.

A router has two identical default routes to 10.0.0.0/24. One route is learned via EIGRP, and the other is a static route. Which of the following commands will set the static route so it's only used in the event the EIGRP route is no longer available?

CORRECT ANSWER - ip route 10.0.0.0 255.0.0.0 192.168.1.254 100 MORE INFORMATION: Adjusting the administrative distance so it is higher than a dynamically learned AD is known as a floating static route. Floating static routes are often used as a failover mechanism in the event the dynamically learned path fails. The proper syntax to change the AD is to simply type it at the end of the next-hop route. The distance can be set to anything between 1 and 255. In this example, the AD must be set higher than 90, as this is the default AD used by internal EIGRP.

Which of the following tools will identify if a CAT5e cable is operating at optimal performance?

Certifier

Broadcast

Communication from one host to all the hosts in the network.

Unicast

Communication from one host to another host only.

Multicast

Communication from one host to few hosts only.

A network administrator has been receiving work orders about poor voice quality crossing a branch T1.The cause is determined to be users running high bandwidth file sharing applications across the T1 sending large packets delaying the smaller voice streams. Which of the following would improve voice quality?

Configure traffic shaping to reduce the bandwidth available to the file sharting application.

Which of the following is the MOST likely cause of a wireless connection dropoff in a wireless G network?

Cordless phones

What is the default 802.1D short spanning tree port cost of a 10 Gbps Ethernet link?

Correct Answer- 2 MORE INFORMATION: By default, the 802.1D path cost for a 10 Gbps link is 2 using the short 16-bit method. If you calculate the same link using the long 32-bit method, you get a default value of 2,000.

Which statement about NTP is true?

Correct Answer- NTP authentication is disabled by default. MORE INFORMATION: By default, NTP authentication is disabled. To configure it, you must set the authentication-key, trusted-key number and then enable the features using the ntp authenticate command.

Your manager has requested you indicate which of the above ports will be Spanning Tree Protocol-designated ports.

Correct Answer- Switch V1, Port Fa0/24; Switch V2, Port Fa0/0; Switch V2, Port Fa0/24 MORE INFORMATION: The first step is to understand which switch will become the root switch. This is done via a process called the STP root bridge election process. According to this process, the switch with the lowest bridge ID will be elected as the root switch. In our network diagram, that's SwitchV2. As per STP protocol, SwitchV2 will have all ports set to STP designated. Ports Fa0/0 on SwitchV1 and SwitchV3 are used to reach the root switch and are, therefore, designated STP root ports. The last set of ports to examine is Fa0/24 on SwitchV1 and SwitchV3. Between these two, one port must be set to blocking mode in order to avoid creating a loop in our network, while the other will be set to forwarding mode. SwitchV1 wins because it has a lower MAC address, so SwitchV1 Fa0/24 is set to forwarding and becomes an STP-designated port, while SwitchV3 Fa0/24 turns to a blocking state. Detailed examples and analysis on STP, bridge election and STP port states can be found on Firewall.cx's STP section.

After carefully examining the network diagram above, select the correct statement regarding broadcast and collision domains

Correct Answer- There are two broadcast domains and seven collision domains. MORE INFORMATION: Each link to a switch -- switch port -- is a separate collision domain. In our diagram, we have two switches and a total of seven links. Hubs -- located in the lower left corner of the image -- do not create separate collision domains per link. That's because traffic entering one port exits all other ports. Routers, on the other hand, create separate broadcast domains, as broadcast packets do not propagate across them.

DNS services are in a failed state on a network. Some users require FQDN to access specific services. A temporary solution would be to:

Create a local host file on the PC.

A company is getting a new sales system that must remain secure and isolated. The network administrator needs to segregate network traffic for security reasons. Currently there is one addressing scheme 10.2.10.x, with a subnet mask of 255.255.255.0.Which of the following methods would BEST help in segregating the traffic?

Creating a new subnet for this system

Which of the following uses pointer records and A records?

DNS server

Which Rapid Spanning Tree Protocol port state is a combination of standard 802.1D STP's disabled, blocking and listening states?

Discarding MORE INFORMATION: Rapid Spanning Tree Protocol (RSTP) defines three port states, compared with 802.1D STP's five states. RSTP combines the disabled, blocking and listening states into a single port state known as discarding. The reason for the combination is because a port in a disabled, blocking or listening state doesn't differ from an STP topology perspective. Each of these states discards all frames and isn't actively learning the media access control (MAC) addresses of connected switches and devices. QUESTION 2

Which of the following protocols allows email to be viewed while remaining on the email server?

IMAP 4

Packet Filtering

Routers can drop or forward packets based on certain criteria like their source and destination. This is also discussed in detail later in the book.

Path Selection

Routers can talk to each other to learn about all the networks connected to various routers and then select the best path to reach a network. This is function is discussed in detail later in the book.

A network technician has been asked to retrieve device statistics, information, and errors. Which of the following tools would the technician likely use?

SNMP

A technician is dispatched to a remote office to install a new NIC in a client computer. After successfully installing and configuring the operating system to recognize the device, the computer still cannot access the network. Which of the following would MOST likely be the problem?

The CAT5 cable is defective

What actions does the DHCP server take when there is an IP address conflict, as shown above?

The IP addresses are removed from the DHCP pool until the conflicts are resolved. MORE INFORMATION: When a Cisco DHCP server discovers a conflict, it will place the IP address into the conflict table, stating the address was conflicting and how it came to that conclusion, as noted under the detection method column. The administrator must examine each IP address and detection method and, when ready, clear the IP addresses from the conflict pool. More information on each detection method and commands to clear them can be found on Firewall.cx's DHCP article.

A user reports that when the phone rings in their house the wireless on their laptops becomes disconnected. Which of the following BEST describes the issue?

The cordless phones are 2.4Ghz which interferes with wireless

Users are reporting that they can access Internet web pages but cannot access the internal company website. Which of the following is the MOST likely source of the problem?

The intranet server is down.

A user contacts a technician and states that they are unable to access the network. The technician discovers that the IP address of the workstation is 169.123.142.34. Which of the following has occurred?

The workstation has obtained an APIPA address.

TCP/IP model 4 layers

application, transport, internet, network access

Transmission Control Protocol (TCP)

provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.

Transport Layer

responsible for providing communication with the application by acknowledging and sequencing the packets to and from the application