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88. TCP and UDP work at transport layer of OSI model or the Host-to-Host layer of DOD Model.
89. Telnet:
90. The “no cdp enable” instruction has to be given at the interface configuration mode, where CDP needs to be disabled. (in this case S0/0).
91. service password-encryption command:
Directs the router to encrypt passwords that are saved in the configuration file. Service password encryption is applied to all passwords, including username passwords, authentication key passwords, the privileged command password, console and virtual terminal line access passwords. This command is primarily useful for keeping unauthorized individuals from viewing your password in your configuration file.
92. The address range and the corresponding binary values for the first
octet of IP classes are as given below:
Class A: 0-127 binary: 00000000-01111111
Class B: 128-191 binary: 10000000 – 10111111
Class C: 192-223 binary:
11000000 – 11011111
Class D: 224-239 binary: 11100000 – 11101111
Note
that the IP address 172.54.17.6 belongs to class B, and hence the applicable
binary address range is 10000000 – 10111111.
93. The auxiliary password is used to set the password for the auxiliary port. Assuming that you are at # prompt, the sequence of commands are:
94. A banner is displayed whenever anyone logs in to your Cisco router. The syntax for configuring the banner is
# symbol signifies the start of the banner message to the router. You will be prompted for the message to be displayed. You need to enter "#" symbol at the end of the message, signifying that the msg has ended.
95. The Catalyst 1900 and 2820 series switches support three types of switching methods:
96. The Cisco router can be configured from many locations.
97. The command "ipx routing" selects IPX as a routing protocol and starts the routing process. Some other important commands are:
98. The command "show CDP neighbors" displays all the neighboring devices connected and their capability. Several capability codes are:
This command displays the following:
1. Neighbor Device ID : The name
of the neighbor device;
2. Local Interface : The interface to which this
neighbor is heard
3. Capability: Capability of this neighboring device
- R for router, S for switch, H for Host etc.
4. Platform: Which type
of device the neighbor is. (2500 router or anything else)
5. Port ID:
The interface of the remote neighbor you receive CDP information
6. Holdtime:
Decremental hold time in seconds
99. The command "terminal no editing" stops all advance editing features.
100. Important CDP Commands:
101. Typical sequence of steps involved in password recovery (on 2501 router) is:
102. The command syntax for configuring RIP version1 on a router is:
Note that the network numbers are specified as either class A, or Class B or Class C; and contain no subnetting information.
The command to configure a static route to network 192.204.1.64/28 from assuming that the default gateway is 192.204.1.2 is:
Syntax: ip route <remote_network> <mask> <default_gateway> [administrative_distance]
103. The correct syntax for setting default route is:
You can also set default route by specifying the interface as below:
The syntax is:
104. The default administrative distances for various protocols are as below:
105. The default port numbers used for some important services are:
When you are accessing a Web page, the browser sends the request over the default port number (For WWW, the default port number is 80). For any reason, If you change the default port number that a Web server listens to, users need to specify the port number in the URL.
106. The distinguishing characteristics of a TCP frame are Sequence Number, Acknowledgment Number, and Window.
107. The following are frequently used OSI layer 2 (data link) protocols:
a. PPP
b. SLIP
c. Frame Relay
d. HDLC
e. Ethernet
f. Token
Ring
108. The following are main features of route summarization in EIGRP:
109. The following are some important commands that can be used to edit and review command history buffer. It will be useful to practice these commands.
110. The following are some Presentation Layer standards:
111. The following are the important characteristics of SDM:
112. The following are true about HDLC encapsulation over serial links:
a. HDLC encapsulation used on Cisco routers is proprietary (uses a Type
field), and may not be compatible with routers manufactured by other vendors
b. It is recommended to use other encapsulation schemes such as PPP when
connecting between a Cisco router and a non-Cisco router instead of HDLC
encapsulation.
113. The following are true about the IP address 132.145.12.5/25
114. The following precautions may be taken to harden network infrastructure:
115. The four layers of DoD model from Top to Bottom are:
116. The Internet architecture provides an unregulated network path to attack innocent hosts. Denial-of-service (DoS) attacks exploit this to target mission-critical services. DoS attacks, are explicit attempts to block legitimate users system access by reducing system availability. Any physical or host-based intrusions are generally addressed through hardened security policies and authentication mechanisms. Although software patching defends against some attacks, it fails to safeguard against DoS flooding attacks, which exploit the unregulated forwarding of Internet packets.
117. MAC sub-layer:
118. The MAC address contains 48 bits expressed as 12 hexadecimal digits. Note that 2 hexadecimal digits represent a byte. Therefore, a MAC address contains 6 bytes. The first 3 bytes represent the manufacturer identification code. The next 3 bytes represent the interface number unique to a given manufacturer. MAC address represents the hardware address and is usually burned into the ROM. A typical MAC address looks like:
xx-xx-xx-xx-xx-xx, where x represents a hexadecimal digit.
Ex: 00-00-0c-12-14-33
Here, 00-00-0c represents the vendor address, and 12-14-33 typically represents the interface serial number. The last 6 hex digits are administered by respective vendors, and unique to a given vendor.
119. The MAC address table of a switch would be empty to begin with. However, it builds the MAC table learning from the frames that arrive at its ports by adding the MAC address and the corresponding port that it had arrived to the MAC table.
120. The maximum allowed cable lengths are as given below:
121. The number of distinct IPs' required in an IP network are:
122. TCP and UDP Protocol Characteristics:
123. The port numbers used by different programs are as below:
124. The purpose of port security is to prevent access to the LAN from un-authorized hosts.
125. The range of numbers from 224.0.0.0 to 239.255.255.255 are used for multicast packets. This is known as Class D address range.
126. The store and forward switch works by first receives the whole packet before retransmission. Cut-through switch mode retransmits a frame as soon as it reads the destination address. Fragment-free switch mode reads the first 64 bytes before retransmission. Therefore, the latency of cut-through and fragment-free switch modes is constant, whereas that of store-and-forward varies depending on the length of the packet.
127. The subnet Id of a host with IP address 165.212.18.5/20 is 165.212.16.0
The available host address range is 165.212.16.1 - 165.212.31.254
Broadcast
address: 165.212.31.255
128. The syntax for ping command is : "ping <destination_address>"
The following are possible responses to "ping" command:
Ping Explanation
Response
U destination Unreachable
C Congestion
experienced
! Successful receipt of echo reply
. Time out
? Packet
type unknown
& Packet time to live exceeded
Ping sends ECMP echo.
Ping can be used with almost any type of Network layer protocols including
IPX, IP, VINES, AppleTalk etc.
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