CCNA试题1-19答案

1. [OxNx] During a TFTP transfer using Cisco Routers what is the numeric value, in decimal, of the destination port field of the User Datagram Protocol (UDP) header?

a) 96
b) 47
c) a random number above 1024
d) 69
e) none of the above

Answer
d) 69

Here is a sampling of other port numbers and the application they are associated with. The first 8 of these protocols are automatically forwarded through the router by using the helper-address command

Trivial File Transfer (TFTP) (port 69)
Domain Name System (port 53)
IEN-116 Name Server (port 42)
Time service (port 37)
NetBIOS Name Server (port 137)
NetBIOS Datagram Server (port 138)
Boot Protocol (BootP) client and server datagrams (port 67)
TACACS service (port 49)
Simple Mail Transfer Protocol (25)
File Transfer Protocol (21)
Simple Network Management Protocol (161)

2. [CxNx] What is the standard encapsulation method used by Cisco routers for the Internet Protocol (IP) on it’s Ethernet interfaces?

a) SNAP
b) ARPA
c) NOVELL-ETHER
d) DARPA
e) Ethernet_802.3

Answer
b) ARPA

SNAP is the default encapsulation for a token ring interface NOVELL-ETHER is the default encapsulation for a ipx interface.

3. [CxNx] What will be the correct command on a Cisco router to set the IP address of an interface assuming you are at the "router(config-if)#" prompt?

a) ip address 1.1.1.1 255.255.255.0
b) ip address 1.1.1.1
c) ip 1.1.1.1
d) ip 1.1.1.1 255.255.255.0
e) none of the above

Answer
a) ip address 1.1.1.1 255.255.255.0

If you are not in the configuration mode, the ip address can be set by using the setup mode.

Configuring interface Ethernet0/0:
Is this interface in use? [yes]:
Configure IP on this interface? [yes]:
IP address for this interface [10.10.10.1]: 10.10.10.1
Number of bits in subnet field [16]: 16
Class A network is 10.0.0.0, 16 subnet bits; mask is /24

Take note when using the setup mode the mask is configured using the number of subnet bits.

4. [CxNx] Which commands will display the IP addresses of all interfaces on a Cisco Router? (Choose all that apply)

a) show ip route
b) show ip address
c) show ip interface
d) show interface
e) display ip addresses

Answer
c) show ip interface
d) show interface

Examples of each of these commands are shown below:

Router_A#sh int e0/0

Ethernet0/0 is up, line protocol is up

Hardware is AmdP2, address is

0010.7b15.bd41

(bia 0010.7b15.bd41)

Internet address is 10.10.10.1/24

MTU 1500 bytes, BW 10000 Kbit,

DLY 1000 usec,

rely 255/255, load 1/255

Encapsulation ARPA, loopback not set,

keepalive set (10 sec)

ARP type: ARPA, ARP Timeout 04:00:00

Last input never, output 00:00:06,

output hang never

Last clearing of "show interface"

counters never

Queueing strategy: fifo

Output queue 0/40, 0 drops;

input queue 0/75,

0 drops

5 minute input rate 0 bits/sec,

0 packets/sec

5 minute output rate 0 bits/sec,

0 packets/sec

0 packets input, 0 bytes,

0 no buffer

Received 0 broadcasts, 0 runts,

0 giants,

0 throttles, 0 input errors, 0 CRC,

0 frame, 0 overrun, 0 ignored,

0 abort

0 input packets with dribble

condition detected

127 packets output, 11802 bytes,

0 underruns

0 output errors, 0 collisions,

2 interface resets

0 babbles, 0 late collision,

0 deferred

0 lost carrier, 0 no carrier

0 output buffer failures, 0 output

buffers swapped out
Router_A#sh ip int e0/0

Ethernet0/0 is up, line protocol is up

Internet address is 10.10.10.1/24

Broadcast address is 255.255.255.255

Address determined by

non-volatile memory

MTU is 1500 bytes

Helper address is not set

Directed broadcast forwarding is enabled

Outgoing access list is not set

Inbound access list is not set

Proxy ARP is enabled

Security level is default

Split horizon is enabled

ICMP redirects are always sent

ICMP unreachables are always sent

ICMP mask replies are never sent

IP fast switching is enabled

IP fast switching on the same

interface is disabled

IP multicast fast switching is enabled

Router Discovery is disabled

IP output packet accounting is disabled

IP access violation accounting is

disabled

TCP/IP header compression is disabled

Probe proxy name replies are disabled

Gateway Discovery is disabled

Policy routing is disabled

Network address translation is disabled


5. [CxNx] Which of the following commands will display the contents of the ARP cache of your Cisco router?

a) show ip arp cache
b) show ip route
c) show ip arp
d) show arp
e) there is no way to display the ARP cache

Answer
c) show ip arp

Example:
Router_A#sh ip arp
Protocol Address Age(min) Hardware Address Type Interface
Internet 1.1.1.2 - 0010.7b15.bd50 ARPA FastEthernet1/0
Internet 10.10.10.1 - 0010.7b15.bd41 ARPA Ethernet0/0


6. [CxNx] Reverse Address Resolution Protocol (RARP) is the process:

a) Where an IP host resolves it’s IP address by broadcasting it’s MAC address to the network and a BOOTP server assigns it an IP address.
b) Where an IP host resolves it’s MAC address by broadcasting to the local network it’s IP address.
c) Where an IP host tries to resolve the MAC address of a destination by sending a network broadcast. The destination responds to the broadcast with it’s MAC address.
d) Where an IP host resolves a destination IP address by sending a broadcast on the local network and the destination host responds with it’s IP address.
e)There is no such process.

Answer
a) Where an IP host resolves it’s IP address by broadcasting it’s MAC address to the network and a BOOTP server assigns it an IP address.

Choice C describes Address Resolution Protocol (ARP). A host never has to resolve it’s own MAC address. The MAC address is burned into the Network Interface card. When the host is booted the MAC address will be loaded into memory.



7. [OxNx] Which of the following applications requires the connection-oriented layer four protocol, TCP? (Choose all that apply)

a) Telnet
b) FTP
c) TFTP
d) SNMP
e) none of the above

Answer
a) Telnet
b) FTP

TFTP and SNMP use layer 4 UDP.


8. [RxNx] Which of the following are link state Routing Protocols.
(Choose all that apply.)

a) IP
b) OSPF
c) RIP
d) EIGRP
e) IS-IS

Answer
b) OSPF
e) IS-IS