In single-site deployments, CUCM servers and IP Phones usually use private IP addresses because there is no need to communicate with the outside IP world. NAT is not configured for the phone subnets, and attacks from the outside are impossible. In multisite deployments, however, IP Security (IPsec) virtual private network (VPN) tunnels can be used between sites. The VPN tunnels allow only intersite communication; access to the protected internal networks is not possible from the outside—only from the other site through the tunnel. Therefore, attacks from the outside are blocked at the gateway. To configure IPsec VPNs, the VPN tunnel must be configured to terminate on the two gateways in the different sites. Sometimes this is not possible; for instance, the two sites may be under different administration, or perhaps security policies do not allow the configuration of IPsec VPNs. In such a case, or when connecting to a public service such as an ITSP, NAT has to be configured for CUCM servers and IP Phones. Cisco calls this Hosted NAT Traversal for Session Border Controllers. In Figure 1-7, Company A and Company B both use IP network 10.0.0.0/8 internally. To communicate over the Internet, the private addresses are translated into public IP addresses. Company A uses public IP network A, and Company B uses public IP network B. All CUCM servers and IP Phones can be reached from the Internet and communicate with each other. As soon as CUCM servers and IP Phones can be reached with public IP addresses, they are subject to attacks from the outside world, introducing potential security issues.
Optimized Call Routing and PSTN Backup
There are two ways to save costs for PSTN calls in a multisite deployment:
• Toll bypass: Calls between sites within an organization that use the IP WAN
instead of the PSTN. The PSTN is used for intersite calls only if calls over the IP WAN are not possible—either because of a WAN failure or because the call is not admitted by Call Admission Control (CAC).
Bandwidth Challenges
Each site in a multisite deployment usually is interconnected by an IP WAN, or occasionally by a metropolitan-area network (MAN) such as Metro Ethernet. Bandwidth on WAN links is limited and relatively expensive. The goal is to use the available bandwidth as efficiently as possible. Unnecessary traffic should be removed from the IP WAN links through content filtering, firewalls, and access control lists (ACL). IP WAN acceleration methods for bandwidth optimization should be considered as well. Any period of congestion could result in service degradation unless QoS is deployed throughout the network. Voice streams are constant and predictable for Cisco audio packets. Typically, the G.729 codec is used across the WAN to best use bandwidth. As a comparison, the G.711 audio codec requires 64 kbps, whereas packetizing the G.711 voice sample in an IP/UDP/RTP header every 20 ms requires 16 kbps plus the Layer 2 header overhead. Voice is sampled every 20 ms, resulting in 50 packets per second (pps). The IP header is 20 bytes, whereas the UDP header is 8 bytes, and the RTP header is 12 bytes. The 40 bytes of header information must be converted to bits to figure out the packet rate of the overhead. Because a byte has 8 bits, 40 bytes * 8 bits in a byte = 320 bits. The 320 bits are sent 50 times per second based on the 20-ms rate (1 millisecond is 1/1000 of a second, and 20/1000 = .02).
Which of the following access list statements would deny traffic from a specific host?
A. Router(config)# access-list 1 deny 172.31.212.74 any
B. Router(config)# access-list 1 deny 10.6.111.48 host
C. Router(config)# access-list 1 deny 172.16.4.13 0.0.0.0
D. Router(config)# access-list 1 deny 192.168.14.132 255.255.255.0
E. Router(config)# access-list 1 deny 192.168.166.127 255.255.255.255
Answer: C
Explanation:
Only choice C is the correct syntax for a specific host. The access list is denying all traffic from the host with IP address 172.16.4.13. It is important to note that in an access list, the subnet mask is the inverse. Normally, a host subnet mask is 255.255.255.255, but in an access list it is 0.0.0.0.
Incorrect Answers:
A. The syntax is incorrect here, as there is no subnet mask at all specified.
B. This would be an acceptable choice, if the "host" keyword were placed in front of the IP address, not after.
D. The subnet mask here includes the entire class C network here, not an individual host.
E. In an access list, the subnet mask is an inverse mask. The mask specified here would be equivalent to all 0's in a subnet mask, meaning that the don't care bits apply to the entire address.
B. Router(config)# access-list 1 deny 10.6.111.48 host
C. Router(config)# access-list 1 deny 172.16.4.13 0.0.0.0
D. Router(config)# access-list 1 deny 192.168.14.132 255.255.255.0
E. Router(config)# access-list 1 deny 192.168.166.127 255.255.255.255
Answer: C
Explanation:
Only choice C is the correct syntax for a specific host. The access list is denying all traffic from the host with IP address 172.16.4.13. It is important to note that in an access list, the subnet mask is the inverse. Normally, a host subnet mask is 255.255.255.255, but in an access list it is 0.0.0.0.
Incorrect Answers:
A. The syntax is incorrect here, as there is no subnet mask at all specified.
B. This would be an acceptable choice, if the "host" keyword were placed in front of the IP address, not after.
D. The subnet mask here includes the entire class C network here, not an individual host.
E. In an access list, the subnet mask is an inverse mask. The mask specified here would be equivalent to all 0's in a subnet mask, meaning that the don't care bits apply to the entire address.
Which one of the access control list statements below will deny all telnet connections to subnet 10.10.1.0/24?
A. access-list 15 deny telnet any 10.10.1.0 0.0.0.255 eq 23
B. access-list 115 deny udp any 10.10.1.0 eq telnet
C. access-list 15 deny tcp 10.10.1.0 255.255.255.0 eq telnet
D. access-list 115 deny tcp any 10.10.1.0 0.0.0.255 eq 23
E. access-list 15 deny udp any 10.10.1.0 255.255.255.0 eq 23
Answer: D
Explanation:
Telnet uses port TCP port 23. Since we are using source and destination IP address information, an extended access list is required. Extended access lists are access lists in the 100-199 range.
Incorrect Answers:
A, C, E. These access lists are numbered 15. Standard access lists are numbered 1-99, and in this case an extended access lists is required.
B. This access list specifies UDP port 23, and TCP port 23 is the port used by telnet.
B. access-list 115 deny udp any 10.10.1.0 eq telnet
C. access-list 15 deny tcp 10.10.1.0 255.255.255.0 eq telnet
D. access-list 115 deny tcp any 10.10.1.0 0.0.0.255 eq 23
E. access-list 15 deny udp any 10.10.1.0 255.255.255.0 eq 23
Answer: D
Explanation:
Telnet uses port TCP port 23. Since we are using source and destination IP address information, an extended access list is required. Extended access lists are access lists in the 100-199 range.
Incorrect Answers:
A, C, E. These access lists are numbered 15. Standard access lists are numbered 1-99, and in this case an extended access lists is required.
B. This access list specifies UDP port 23, and TCP port 23 is the port used by telnet.
Which of the following are benefits provided with access control lists (ACLs)?
A. ACLs monitor the number of bytes and packets.
B. Virus detection.
C. ACLs dentify interesting traffic for DDR.
D. ACLs provide IP route filtering.
E. ACLs provide high network availability.
F. ACLs classify and organize network traffic.
Explanation:
IP access control lists allow a router to discard some packets based on criteria defined by the network engineer. The goal of these filters is to prevent unwanted traffic in the network - whether to prevent hackers from penetrating the network or just to prevent employees from using systems they should not be using.
IP access lists can also be used to filter routing updates, to match packets for
prioritization, to match packets for prioritization, to match packets for VPN tunneling, and to match packets for implementing quality of service features. It is also used to specify the interesting traffic, which is used to trigger ISDN and Dial on Demand Routing (DDR) calls.
Reference:
CCNA Self-Study CCNA ICND exam certification Guide (Cisco Press, ISBN
1-58720-083-X) Page 427
Incorrect Answers:
A, F. ACLs do not provide for management and traffic analysis functions such as the monitoring and organization of network packets.
routinely provide for virus detection and removal.
E. ACLs alone do not provide for any additional level of network availability.
B. Virus detection.
C. ACLs dentify interesting traffic for DDR.
D. ACLs provide IP route filtering.
E. ACLs provide high network availability.
F. ACLs classify and organize network traffic.
Explanation:
IP access control lists allow a router to discard some packets based on criteria defined by the network engineer. The goal of these filters is to prevent unwanted traffic in the network - whether to prevent hackers from penetrating the network or just to prevent employees from using systems they should not be using.
IP access lists can also be used to filter routing updates, to match packets for
prioritization, to match packets for prioritization, to match packets for VPN tunneling, and to match packets for implementing quality of service features. It is also used to specify the interesting traffic, which is used to trigger ISDN and Dial on Demand Routing (DDR) calls.
Reference:
CCNA Self-Study CCNA ICND exam certification Guide (Cisco Press, ISBN
1-58720-083-X) Page 427
Incorrect Answers:
A, F. ACLs do not provide for management and traffic analysis functions such as the monitoring and organization of network packets.
routinely provide for virus detection and removal.
E. ACLs alone do not provide for any additional level of network availability.
Which command will configure a default route on a router?
A. router(config)# ip route 0.0.0.0 10.1.1.0 10.1.1.1
B. router(config)# ip default-route 10.1.1.0
C. router(config)# ip default-gateway 10.1.1.0
D. router(config)# ip route 0.0.0.0 0.0.0.0 10.1.1.1
Answer: D
Explanation:
The command "IP route 0.0.0.0 0.0.0.0" command is used to
configure a default route. In this case, a default route with a next hop IP address of
10.1.1.1 was configured.
Incorrect Answers:
A. This will be an invalid route, since the "10.1.1.0" value will specify the network mask, which in this case is invalid.
B, C. These commands are invalid. The command "ip default-network" could be used, bit not "ip default-route" or "ip default-gateway".
B. router(config)# ip default-route 10.1.1.0
C. router(config)# ip default-gateway 10.1.1.0
D. router(config)# ip route 0.0.0.0 0.0.0.0 10.1.1.1
Answer: D
Explanation:
The command "IP route 0.0.0.0 0.0.0.0
configure a default route. In this case, a default route with a next hop IP address of
10.1.1.1 was configured.
Incorrect Answers:
A. This will be an invalid route, since the "10.1.1.0" value will specify the network mask, which in this case is invalid.
B, C. These commands are invalid. The command "ip default-network" could be used, bit not "ip default-route" or "ip default-gateway".
You work as a network engineer at IGCT Groups.You are required to allow establishment of a Telnet session with a router. Which set command.
A. TestKingC(config)# line console 0
TestKingC(config-line)# enable password testking
B. TestKingC(config)# line console 0
TestKingC(config-line)# enable secret testking
TestKingC(config-line)# login
C. TestKingC(config)# line console 0
TestKingC(config-line)# password testking
TestKingC(config-line)# login
D. TestKingC(config)# line vty 0
TestKingC(config-line)# enable password testking
E. TestKingC(config)# line vty 0
TestKingC(config-line)# enable secret testking
TestKingC(config-line)# login
F. TestKingC(config)# line vty 0
TestKingC(config-line)# password testking
TestKingC(config-line)# login
Answer: F
Explanation:
CLI Password Configuration:
Access From Password Type Configuration
Console Console password Line console 0
Login
Password faith
Auxiliary Auxiliary password Line aux 0
Login
Password hope
Telent Vty password Line vty 0 4
Login
Password love
TestKingC(config-line)# enable password testking
B. TestKingC(config)# line console 0
TestKingC(config-line)# enable secret testking
TestKingC(config-line)# login
C. TestKingC(config)# line console 0
TestKingC(config-line)# password testking
TestKingC(config-line)# login
D. TestKingC(config)# line vty 0
TestKingC(config-line)# enable password testking
E. TestKingC(config)# line vty 0
TestKingC(config-line)# enable secret testking
TestKingC(config-line)# login
F. TestKingC(config)# line vty 0
TestKingC(config-line)# password testking
TestKingC(config-line)# login
Answer: F
Explanation:
CLI Password Configuration:
Access From Password Type Configuration
Console Console password Line console 0
Login
Password faith
Auxiliary Auxiliary password Line aux 0
Login
Password hope
Telent Vty password Line vty 0 4
Login
Password love
You are implementing a new frame relay network to provide connectivity between you offices. To do this, you set up the frame relay network using point
You are implementing a new frame relay network to provide connectivity between
you offices. To do this, you set up the frame relay network using point-to-point
sub interfaces.
Which of the following does NOT need to be configured?
A. The Frame Relay encapsulation on the physical interface.
B. The local DLCI on each subinterface.
C. An IP address on the physical interface.
D. The subinterface type as point-to-point.
Answer: C
Explanation:
When using point to point subinterfaces in a frame relay network, the subinterfaces will each have their own IP addresses and will each be contained within their own IP subnet.
The physical interface does not require an IP address. Incorrect Answers:
A. The physical interface will need to be configured with a layer two encapsulation type, so in this case it must be frame relay.
B. The subinterfaces will have the local DLCI assigned to each one, using the
"frame-relay interface-dlci" command for each of the subinterfaces.
D. Each subinterface should be configured as a point to point network type.
you offices. To do this, you set up the frame relay network using point-to-point
sub interfaces.
Which of the following does NOT need to be configured?
A. The Frame Relay encapsulation on the physical interface.
B. The local DLCI on each subinterface.
C. An IP address on the physical interface.
D. The subinterface type as point-to-point.
Answer: C
Explanation:
When using point to point subinterfaces in a frame relay network, the subinterfaces will each have their own IP addresses and will each be contained within their own IP subnet.
The physical interface does not require an IP address. Incorrect Answers:
A. The physical interface will need to be configured with a layer two encapsulation type, so in this case it must be frame relay.
B. The subinterfaces will have the local DLCI assigned to each one, using the
"frame-relay interface-dlci" command for each of the subinterfaces.
D. Each subinterface should be configured as a point to point network type.
Which one of the following commands would you enter to terminate a VTY line session?
B. disable
C. disconnect
D. suspend
E. exit
F. None of the above
Answer: E
Explanation:
A VTY line is a telnet session. To end a telnet session from a remote device, enter the exit or logout command.
Incorrect Answers:
A, B, C, D. These are all invalid commands.
C. disconnect
D. suspend
E. exit
F. None of the above
Answer: E
Explanation:
A VTY line is a telnet session. To end a telnet session from a remote device, enter the exit or logout command.
Incorrect Answers:
A, B, C, D. These are all invalid commands.
RIP version 2 is being used as the routing protocol within the Office network. What does RIP version 2 use to prevent routing loops?
A. CIDR
B. Split horizon
C. Authentication
D. Classless masking
E. Hold-down timers
F. Multicast routing updates
G. Path Vectoring
Answer: B, E
Explanation:
Distance Vector routing protocols employ the split horizon mechanism to reduce the possibility of routing loops. Split horizon blocks information about routes from being advertised by a router out of any interface from which that information originated.
RIP versions 1 and 2 also use the concept of hold timers. When a destination has become unreachable (or the metric has increased enough to cause poisoning), the destination goes into "holddown". During this state, no new path will be accepted for the same destination for this amount of time. The hold time indicates how long this state should last.
Incorrect Answers:
A, C, D, F. Although these are all features and functions of RIP version 2, they are not mechanisms used to prevent routing loops.
G. Path Vectoring is a concept used by BGP routers. RIP version 1 and 2 are considered to be distance vector routing protocols.
B. Split horizon
C. Authentication
D. Classless masking
E. Hold-down timers
F. Multicast routing updates
G. Path Vectoring
Answer: B, E
Explanation:
Distance Vector routing protocols employ the split horizon mechanism to reduce the possibility of routing loops. Split horizon blocks information about routes from being advertised by a router out of any interface from which that information originated.
RIP versions 1 and 2 also use the concept of hold timers. When a destination has become unreachable (or the metric has increased enough to cause poisoning), the destination goes into "holddown". During this state, no new path will be accepted for the same destination for this amount of time. The hold time indicates how long this state should last.
Incorrect Answers:
A, C, D, F. Although these are all features and functions of RIP version 2, they are not mechanisms used to prevent routing loops.
G. Path Vectoring is a concept used by BGP routers. RIP version 1 and 2 are considered to be distance vector routing protocols.
Which of the following routing protocols do NOT support VLSM (variable length subnet masking)?
A. RIPv1
B. IGRP
C. EIGRP
D. OSPF
E. IS-IS
F. RIPv2
Answer: A, B
Explanation:
RIP version 1 and IGRP are classful IP routing protocols. They do not support variable length subnet masks.
Incorrect Answers:
C, D, E, F. Static routing, OSPF, IS-IS, EIGRP, BGP, and RIP version 2 all support
VLSM.
B. IGRP
C. EIGRP
D. OSPF
E. IS-IS
F. RIPv2
Answer: A, B
Explanation:
RIP version 1 and IGRP are classful IP routing protocols. They do not support variable length subnet masks.
Incorrect Answers:
C, D, E, F. Static routing, OSPF, IS-IS, EIGRP, BGP, and RIP version 2 all support
VLSM.
You are a network administrator and you need to implement a routing protocol on your network that provides:
* Scalability
* VLSM support
* Minimal overhead
* Support for connecting networks using routers of multiple vendors
Which of the following routing protocol would best serve your needs?
Options :
A. VTP
B. RIP version 1
C. EIGRP
D. OSPF
E. IGRP
F. CDP
Answer: D
Explanation:
Since one of the requirements is that the routing protocol must support other vendors, our only choices are RIP and OSPF. Since RIP version 1 does not support VLSM, OSPF is the only choice.
Incorrect Answers:
A. VTP is the VLAN Trunking Protocol. This is not a routing protocol.
B. RIP version one does not support VLSM. Note that RIPv2 does support VLSM, and would be a valid choice.
C, E. EIGRP and IGRP are Cisco proprietary routing protocols, and are not supported by other vendors.
F. CDP is the Cisco Discovery Protocol, which is used to exchange information between Cisco devices. It can only be used between Cisco routers and switches, and it is not a routing protocol.
* VLSM support
* Minimal overhead
* Support for connecting networks using routers of multiple vendors
Which of the following routing protocol would best serve your needs?
Options :
A. VTP
B. RIP version 1
C. EIGRP
D. OSPF
E. IGRP
F. CDP
Answer: D
Explanation:
Since one of the requirements is that the routing protocol must support other vendors, our only choices are RIP and OSPF. Since RIP version 1 does not support VLSM, OSPF is the only choice.
Incorrect Answers:
A. VTP is the VLAN Trunking Protocol. This is not a routing protocol.
B. RIP version one does not support VLSM. Note that RIPv2 does support VLSM, and would be a valid choice.
C, E. EIGRP and IGRP are Cisco proprietary routing protocols, and are not supported by other vendors.
F. CDP is the Cisco Discovery Protocol, which is used to exchange information between Cisco devices. It can only be used between Cisco routers and switches, and it is not a routing protocol.
In network that support VLSM, which network mask should be used for point-to-point WAN links in order to reduce waste of IP addresses?
A. /24
B. /30
C. /27
D. /26
E. /32
Answer: B
Explanation:
A 30-bit mask is used to create subnet's with two valid host addresses. This is the exact number needed for a point-to-point connection.
B. /30
C. /27
D. /26
E. /32
Answer: B
Explanation:
A 30-bit mask is used to create subnet's with two valid host addresses. This is the exact number needed for a point-to-point connection.
What is the maximum number of IP addresses that can be assigned to hosts on a local subnet that use the 255.255.255.224 subnet mask?
A. 14
B. 15
C. 16
D. 30
E. 31
F. 32
Answer: D
Explanation:
The subnet mask 255.255.255.224 means that there are 27 network bits. The remaining 5 bits are the host bits. The maximum possible combinations with 5 bits are 25 = 32. As all zero's and all one's hosts are not allowed so, maximum number of valid hosts with the mask 255.255.255.224 are 25 -2 =32-2 = 30 Hosts
B. 15
C. 16
D. 30
E. 31
F. 32
Answer: D
Explanation:
The subnet mask 255.255.255.224 means that there are 27 network bits. The remaining 5 bits are the host bits. The maximum possible combinations with 5 bits are 25 = 32. As all zero's and all one's hosts are not allowed so, maximum number of valid hosts with the mask 255.255.255.224 are 25 -2 =32-2 = 30 Hosts
If an Ethernet port on router was assigned an IP address of 172.16.112.1/20, what is the maximum number of hosts allowed on this subnet?
A. 1024
B. 2046
C. 4094
D. 4096
E. 8190
Answer: C
Explanation:
Given IP address of 172.16.112.1 / 20,
subnet mask: 255.255.240.0
max. num of hosts =(( 2^12) -2 ) = 4096-2 = 4094
B. 2046
C. 4094
D. 4096
E. 8190
Answer: C
Explanation:
Given IP address of 172.16.112.1 / 20,
subnet mask: 255.255.240.0
max. num of hosts =(( 2^12) -2 ) = 4096-2 = 4094
Which of the following IP addresses is a private IP address?
A. 12.0.0.1
B. 168.172.19.39
C. 172.20.14.36
D. 172.33.194.30
E. 192.168.42.34
Answer: C, E
Explanation:
RFC 1918 Private Address Space:
Range of IP Addresses Class of Networks Number of Network
10.0.0.0 to
10.255.255.255.255
A 1
172.16.0.0 to
172.31.255.255
B 16
192.168.0.0 to
192.168.255.255
C 256
B. 168.172.19.39
C. 172.20.14.36
D. 172.33.194.30
E. 192.168.42.34
Answer: C, E
Explanation:
RFC 1918 Private Address Space:
Range of IP Addresses Class of Networks Number of Network
10.0.0.0 to
10.255.255.255.255
A 1
172.16.0.0 to
172.31.255.255
B 16
192.168.0.0 to
192.168.255.255
C 256
Which of the following are true regarding a network using a subnet mask of 255.255.248.0?
A. It corresponds to a Class A address with 13 bits borrowed.
B. It corresponds to a Class B address with 4 bits borrowed.
C. The network address of the last subnet will have 248 in the 3rd octet.
D. The first 21 bits make the host portion of the address.
E. This subnet mask allows for 16 total subnets to be created.
F. The subnetwork numbers will be in multiples of 8.
Answer: A, C, F
Explanation:
This subnet mask includes the first 5 bits within the third octet, so for a class A address 13 bits will be used for the mask (8 bits in the second octet plus 5 in the third).
Since the first 5 bits are used in this octet, that means that remaining 3 bits in this octet will be available for hosts, so each network will be a factor of 8, making the last available subnet with a .248 in the third octet.
B. It corresponds to a Class B address with 4 bits borrowed.
C. The network address of the last subnet will have 248 in the 3rd octet.
D. The first 21 bits make the host portion of the address.
E. This subnet mask allows for 16 total subnets to be created.
F. The subnetwork numbers will be in multiples of 8.
Answer: A, C, F
Explanation:
This subnet mask includes the first 5 bits within the third octet, so for a class A address 13 bits will be used for the mask (8 bits in the second octet plus 5 in the third).
Since the first 5 bits are used in this octet, that means that remaining 3 bits in this octet will be available for hosts, so each network will be a factor of 8, making the last available subnet with a .248 in the third octet.
Regarding DHCP (dynamic host configuration protocol), which two of the following choices below are true?
A. The DHCP Discover message uses FF-FF-FF-FF-FF as the Layer 2 destination
address.
B. The DHCP Discover message uses UDP as the transport layer protocol.
C. The DHCP Discover message uses a special Layer 2 multicast address as the
destination address.
D. The DHCP Discover message uses TCP as the transport layer protocol.
E. The DHCP Discover message does not use a Layer 2 destination address.
F. The DHCP Discover message does not require a transport layer protocol.
Answer: A, B
Explanation:
DHCP uses UDP as its transport protocol. DHCP messages from a client to a server are sent to the DHCP server port (UDP port 67), and DHCP messages from a server to a client are sent to the DHCP client port (UDP port 68).The client broadcasts a DHCPDISCOVER message on its local physical subnet. The DHCPDISCOVER message may include options that suggest values for the network address and lease duration.
BOOTP relay agents may pass the message on to DHCP servers not on the same physical subnet.
Each server may respond with a DHCPOFFER message that includes an available
network address in the "ipaddr" field (and other configuration parameters in DHCP
options). Servers need not reserve the offered network address, although the protocol will work more efficiently if the server avoids allocating the offered network address to another client. The server unicasts the DHCPOFFER message to the client (using the DHCP/BOOTP relay agent if necessary) if possible, or may broadcast the message to a broadcast address (preferably 255.255.255.255) on the client's subnet.Incorrect Answers:
C. DHCP messages are broadcast to the "all hosts" address. IP multicast addresses are not used.
D. UDP is used, not TCP.
E. Since DHCP is used so that a client can obtain an IP address, a layer two destination address must be used, as the layer 3 IP address does not yet exist on the client for the return traffic.
F. DHCP, along with nearly every other type of traffic, requires the use of a transport layer protocol.
address.
B. The DHCP Discover message uses UDP as the transport layer protocol.
C. The DHCP Discover message uses a special Layer 2 multicast address as the
destination address.
D. The DHCP Discover message uses TCP as the transport layer protocol.
E. The DHCP Discover message does not use a Layer 2 destination address.
F. The DHCP Discover message does not require a transport layer protocol.
Answer: A, B
Explanation:
DHCP uses UDP as its transport protocol. DHCP messages from a client to a server are sent to the DHCP server port (UDP port 67), and DHCP messages from a server to a client are sent to the DHCP client port (UDP port 68).The client broadcasts a DHCPDISCOVER message on its local physical subnet. The DHCPDISCOVER message may include options that suggest values for the network address and lease duration.
BOOTP relay agents may pass the message on to DHCP servers not on the same physical subnet.
Each server may respond with a DHCPOFFER message that includes an available
network address in the "ipaddr" field (and other configuration parameters in DHCP
options). Servers need not reserve the offered network address, although the protocol will work more efficiently if the server avoids allocating the offered network address to another client. The server unicasts the DHCPOFFER message to the client (using the DHCP/BOOTP relay agent if necessary) if possible, or may broadcast the message to a broadcast address (preferably 255.255.255.255) on the client's subnet.Incorrect Answers:
C. DHCP messages are broadcast to the "all hosts" address. IP multicast addresses are not used.
D. UDP is used, not TCP.
E. Since DHCP is used so that a client can obtain an IP address, a layer two destination address must be used, as the layer 3 IP address does not yet exist on the client for the return traffic.
F. DHCP, along with nearly every other type of traffic, requires the use of a transport layer protocol.
Which protocol below uses TCP port 443?
A. HTML
B. HTTPS
C. TFTP
D. Telnet
E. SMTP
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.
B. HTTPS
C. TFTP
D. Telnet
E. SMTP
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.
Which protocol automates all of the following functions for hosts on a network: IP configuration, IP addresses, subnet masks, default gateways,and DNS
A. CDP
B. SNMP
C. DHCP
D. ARP
E. DNS
F. None of the above
Answer: C
Explanation:
DHCP uses the concept of the client making a request and the server supplying the IP address to the client, plus other information such as the default gateway, subnet mask, DNS IP address, and other information.
Incorrect Answers:
A. CDP is the Cisco Discovery Protocol. It is used by Cisco devices at the data link layer to obtain information about their directly connected neighbors.
B. SNMP is the Simple Network Management Protocol. This is used for the maintenance, management, and monitoring of network devices.
D. ARP is the Address Resolution Protocol, which is used to resolve layer 2 MAC
addresses to layer 3 IP addresses.
E. DNS is the Domain Name Service. It is used to resolve domain names to IP addresses. The IP address location of primary and secondary DNS resolver servers can be obtained for hosts using DHCP.
Which three address ranges are used for internal private address blocks as defined by RFC 1918?
A. 0.0.0.0 to 255.255.255
B. 10.0.0.0 to 10.255.255.255
C. 172.16.0.0 to 172.16.255.255
D. 172.16.0.0 to 172.31.255.255
E. 127.0.0.0. to 127.255.255.255
F. 192.168.0.0 to 192.168.255.255
G. 224.0.0.0 to 239.255.255.255
Answer: B, D, F
Explanation:
RFC 1918 defines three different IP address ranges as private, meaning that they can be used by any private network for internal use, and these ranges are not to be used in the Internet. The class A private range is 10.0.0.0 to 10.255.255.255. The class B address
range is 172.16.0.0 to 172.31.255.255. The class C private IP address range is 192.168.0.0 to 192.168.255.255.
Incorrect Answers:
A. The 0.0.0.0 network address is invalid and can not be used.
C. The correct address range is 172.16.X.X through 172.31.X.X
B. 10.0.0.0 to 10.255.255.255
C. 172.16.0.0 to 172.16.255.255
D. 172.16.0.0 to 172.31.255.255
E. 127.0.0.0. to 127.255.255.255
F. 192.168.0.0 to 192.168.255.255
G. 224.0.0.0 to 239.255.255.255
Answer: B, D, F
Explanation:
RFC 1918 defines three different IP address ranges as private, meaning that they can be used by any private network for internal use, and these ranges are not to be used in the Internet. The class A private range is 10.0.0.0 to 10.255.255.255. The class B address
range is 172.16.0.0 to 172.31.255.255. The class C private IP address range is 192.168.0.0 to 192.168.255.255.
Incorrect Answers:
A. The 0.0.0.0 network address is invalid and can not be used.
C. The correct address range is 172.16.X.X through 172.31.X.X
What statements are true regarding ICMP packets?
A. They acknowledge receipt of TCP segments.
B. They guarantee datagram delivery.
C. They can provide hosts with information about network problems.
D. They are encapsulated within IP datagrams.
E. They are encapsulated within UDP datagrams.
Answer: C, D
Explanation:
ping may be used to find out whether the local machines are connected to the network or whether a remote site is reachable. This tool is a common network tool for determining the network connectivity which uses ICMP protocol instead of TCP/IP and UDP/IP. This protocol is usually associated with the network management tools which provide network information to network administrators, such as ping and traceroute (the later also uses the UDP/IP protocol).
ICMP is quite different from the TCP/IP and UDP/IP protocols. No source and
destination ports are included in its packets. Therefore, usual packet-filtering rules for TCP/IP and UDP/IP are not applicable. Fortunately, a special "signature" known as the packet's Message type is included for denoting the purposes of the ICMP packet. Most commonly used message types are namely, 0, 3, 4, 5, 8, 11, and 12 which represent echo reply, destination unreachable, source quench, redirect, echo request, time exceeded, and parameter problem respectively.
In the ping service, after receiving the ICMP "echo request" packet from the source location, the destination
Incorrect Answers
ICMP is an IP protocol so A and E are incorrect.
ICMP doesn't guarantee datagram delivery so B is wrong as well.
B. They guarantee datagram delivery.
C. They can provide hosts with information about network problems.
D. They are encapsulated within IP datagrams.
E. They are encapsulated within UDP datagrams.
Answer: C, D
Explanation:
ping may be used to find out whether the local machines are connected to the network or whether a remote site is reachable. This tool is a common network tool for determining the network connectivity which uses ICMP protocol instead of TCP/IP and UDP/IP. This protocol is usually associated with the network management tools which provide network information to network administrators, such as ping and traceroute (the later also uses the UDP/IP protocol).
ICMP is quite different from the TCP/IP and UDP/IP protocols. No source and
destination ports are included in its packets. Therefore, usual packet-filtering rules for TCP/IP and UDP/IP are not applicable. Fortunately, a special "signature" known as the packet's Message type is included for denoting the purposes of the ICMP packet. Most commonly used message types are namely, 0, 3, 4, 5, 8, 11, and 12 which represent echo reply, destination unreachable, source quench, redirect, echo request, time exceeded, and parameter problem respectively.
In the ping service, after receiving the ICMP "echo request" packet from the source location, the destination
Incorrect Answers
ICMP is an IP protocol so A and E are incorrect.
ICMP doesn't guarantee datagram delivery so B is wrong as well.
exhibit displays the partial contents of encapsulation header.
A. This is a UDP header
B. This is an OSI layer 4 header.
C. This is traffic from an FTP server.
D. This is traffic from an Telnet client.
E. The last PDU received in this session had a sequence number of 292735.
Answer: B, C, E
Explanation:
As the header contains the sequence number and ACK number fields, it represents a TCP header. Choice B is correct as TCP works on Layer 4 i.e. Transport Layer.
Source Port mentioned in the header is 21 which indicate it is FTP Traffic because FTP uses port 20 and 21 for data and control. So choice C is correct.
The acknowledgment number refers to the sequence number of the last PDU received, which is 292735, making choice E also correct.
B. This is an OSI layer 4 header.
C. This is traffic from an FTP server.
D. This is traffic from an Telnet client.
E. The last PDU received in this session had a sequence number of 292735.
Answer: B, C, E
Explanation:
As the header contains the sequence number and ACK number fields, it represents a TCP header. Choice B is correct as TCP works on Layer 4 i.e. Transport Layer.
Source Port mentioned in the header is 21 which indicate it is FTP Traffic because FTP uses port 20 and 21 for data and control. So choice C is correct.
The acknowledgment number refers to the sequence number of the last PDU received, which is 292735, making choice E also correct.
Catalyst switches utilize a special technology to identify and prevent topology loops and ensure that data flows properly through single network path
A. VTP
B. ISL
C. 802.1Q
D. STP
E. None of the above
Answer: D
Explanation:
Catalyst switches use the STP (spanning tree protocol) to prevent loops and to ensure data flows through a single network path. A separate instance of the STP mechanism is applied to every individual VLAN that is configured on the Catalyst switch.
Incorrect Answers:
A. VTP is the VLAN Trunking Protocol, which is used by Catalyst switches to pass VLAN information between switches. By itself, it does not provide any mechanism for detecting and preventing loops.
B, C. Inter-Switch Link (ISL) and 802.1Q are encapsulation types used for the creation of trunks. ISL is Cisco proprietary and 802.1Q is the industry standard method, but neither of these two options provide for any way to prevent a layer 2 loop in the network.
What are two characteristics of "store and forward" switching? (Select two answer choices)
A. Latency fluctuates regardless of frame size.
B. The switch receives the complete frame before beginning to forward it.
C. Latency through the switch varies with frame length.
D. The switch checks the destination address upon receipt of headers.
Answer: B, C
Explanation:
With store-and-forward, the entire frame is received by the switch before the first bit of the frame is forwarded.
As soon as the incoming switch port receives enough of the frame to see the destination MAC address, the forwarding decision is made and the frame is transmitted out the appropriate outgoing port to the destination device. So, each frame might experience slightly less latency. Store and forward switching may add latency when compared to
other switching methods such as cut through, but it can reduce the amount of errors that become forwarded through a network.
Reference:
CCNA Self-Study CCNA INTRO exam certification Guide (Cisco Press, ISBN 1-58720-094-5) Page 243
Incorrect Answers:
A. The amount of latency that is introduced with this method of switching is dependent on the size of the frame, as the switch must wait to receive the entire frame before sending it.
D. The switch must wait for the entire frame before forwarding it on, and not just the headers.
Leading the way in IT testing and certification tools, You want your Catalyst switch to implement a switching method that holds a packet in its memory
Leading the way in IT testing and certification tools, You want your Catalyst switch to implement a switching method that holds a packet in its memory until the data portion of the respected packet reaches the switch. Which method should you employ on your Catalyst switch?
A. Fast Forward
B. Store and forward
C. Frag-free
D. None of the above
Answer: C
Explanation:
Fragment Free switching filters out the majority of packet errors before forwarding begins. In a properly functioning network, most packet "errors" are due to collisions which are resolved within the first 64 bytes of the packet. These collisions cause packet fragments. After a packet has successfully passed this fragment threshold, it will continue to be received without error with near-certainty. (The next biggest cause of failure arises from "late" collisions which can occur when the network is physically interrupted.) This is how the Fragment Free option works. Fragment Free switching waits until the received packet passes the 64-byte fragment threshold and then forwards the packet.
Incorrect Answers:
A. Fast Forward switching is optimized for performance. It offers the lowest level of latency by immediately forwarding a packet upon receipt of only the destination address (after the first 6 bytes are received). Because Fast Forward does not wait until the entire packet is received before forwarding, this form of switching may sometimes relay a packet that has an error. Although this will be an infrequent occurrence and the destination network adapter will discard the faulty packet upon receipt, this superfluous traffic may be deemed unacceptable in certain environments. Such cut-through overhead can be reduced by using the Fragment Free option.
B. Another switching mode supported by Catalystswitches is the traditional
Store-and-Forward bridging mode. Complete packets are stored and checked for errors prior to transmission. Latency varies by packet size since the entire packet needs to be received prior to transmission.
A. Fast Forward
B. Store and forward
C. Frag-free
D. None of the above
Answer: C
Explanation:
Fragment Free switching filters out the majority of packet errors before forwarding begins. In a properly functioning network, most packet "errors" are due to collisions which are resolved within the first 64 bytes of the packet. These collisions cause packet fragments. After a packet has successfully passed this fragment threshold, it will continue to be received without error with near-certainty. (The next biggest cause of failure arises from "late" collisions which can occur when the network is physically interrupted.) This is how the Fragment Free option works. Fragment Free switching waits until the received packet passes the 64-byte fragment threshold and then forwards the packet.
Incorrect Answers:
A. Fast Forward switching is optimized for performance. It offers the lowest level of latency by immediately forwarding a packet upon receipt of only the destination address (after the first 6 bytes are received). Because Fast Forward does not wait until the entire packet is received before forwarding, this form of switching may sometimes relay a packet that has an error. Although this will be an infrequent occurrence and the destination network adapter will discard the faulty packet upon receipt, this superfluous traffic may be deemed unacceptable in certain environments. Such cut-through overhead can be reduced by using the Fragment Free option.
B. Another switching mode supported by Catalystswitches is the traditional
Store-and-Forward bridging mode. Complete packets are stored and checked for errors prior to transmission. Latency varies by packet size since the entire packet needs to be received prior to transmission.
What are some characteristics of the typical VLAN arrangement?
A. VLANs logically divide a switch into multiple, independent switches at Layer 2.
B. Trunk links can carry traffic for multiple VLANs.
C. VLAN implementation significantly increases traffic due to added trunking
information.
D. A VLAN can span multiple switches.
E. VLANs extend the collision domain to include multiple switches.
F. VLANs typically decrease the number of multiple switches.
Answer: A, B, D
Explanation:
VLANs give you the power of making virtual LAN networks to subdivide collision
domains into smaller units of functionality. Without being limited by physical location.
A is correct because that is the exact function of a VLAN. B is correct because trunk links
are used to carry traffic for multiple VLANs. D is correct because a VLAN can and often
does span across multiple switches, through the use of VTP
Incorrect Answers:
C. This choice is incorrect because although trunking information uses bandwidth, the
amount isn't at all significant.
E. This is incorrect because VLANs do the exact opposite, and are used to segment
collision domains.
F. This is incorrect because VLANs themselves have no power in decreasing the numbers
of multiple switches.
B. Trunk links can carry traffic for multiple VLANs.
C. VLAN implementation significantly increases traffic due to added trunking
information.
D. A VLAN can span multiple switches.
E. VLANs extend the collision domain to include multiple switches.
F. VLANs typically decrease the number of multiple switches.
Answer: A, B, D
Explanation:
VLANs give you the power of making virtual LAN networks to subdivide collision
domains into smaller units of functionality. Without being limited by physical location.
A is correct because that is the exact function of a VLAN. B is correct because trunk links
are used to carry traffic for multiple VLANs. D is correct because a VLAN can and often
does span across multiple switches, through the use of VTP
Incorrect Answers:
C. This choice is incorrect because although trunking information uses bandwidth, the
amount isn't at all significant.
E. This is incorrect because VLANs do the exact opposite, and are used to segment
collision domains.
F. This is incorrect because VLANs themselves have no power in decreasing the numbers
of multiple switches.
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