CCNA试题72-78答案
72. [xINx] The size of a window in a TCP segment establishes what? (Choose one.)
a) The maximum number of bytes that a single frame may not exceed
b) The allowable bandwidth for this TCP session
c) The number of octets that the receiver must be willing to accept
d) The number of 32-bit words in the header
e) The number of octets that the sender is willing to accept
Answer
e) The number of octets that the sender is willing to accept
73. [xINx] Which protocols are best described as connection-oriented and reliable? (Choose two.)
a) UDP
b) IP
c) TCP
d) IPX
e) TCP over IP
f) UDP over IP
Answer
c) TCP
e) TCP over IP
This question is meant to be a little tricky. TCP is layer 4, which uses IP at layer 3.
74. [xINx] A Telnet session to a remote host would be addressed to what port number at the remote host? (Choose one.)
a) UDP port 53
b) TCP port 53
c) UDP port 21
d) TCP port 21
e) UDP port 161
f) TCP port 23
Answer
f) TCP port 23
In the capture below NetXray interpolates the data and shows a source port of 1074 to a destination port of telnet. Refer to the data below the highlighted portion. 0x17 is 1*161 + 7* 160 = 23.
75. [xINx] TCP "source" port number(s): (Choose the one that best describes.)
a) Depends on the application being accessed on the destination host.
b) Depends on the application running on the source host.
c) Are usually assigned by the source host, and are typically some number greater than 1023.
d) Are assigned by the source host and are usually one of the "well known" port numbers.
e) Must be negotiated by the sender and receiver during session setup.
Answer
c) Are usually assigned by the source host, and are typically some number greater than 1023.
The source port in the following capture is 1074:
76. [xINx] In a TCP acknowledgment, the ack number refers to: (Choose one.)
a) A sequential number beginning with 1, and incremented by 1 with each exchange, that identifies this exchange of packets as being complete
b) The number of the packet expected next
c) The number of the packet expected next, plus 1
d) A number agreed upon at session establishment, which will be used by the receiver to indicate a successful exchange of packets
e) TCP does not use acknowledgments.
Answer
b) The number of the packet expected next
This number is the previous Sequence number +1.
Check out the sequence and the acknowledgement numbers below:
Reference the diagram and configurations below for Questions 77 and 78:
Router_C#sh run
Building configuration...
Current configuration:
!
version 11.2
!
hostname Router_C
!
!
appletalk routing
ipx routing 0060.09c3.df60
!
interface Ethernet0
ip address 172.16.1.1 255.255.255.0
appletalk cable-range 100-105 103.243
appletalk zone right
ipx network DAD
!
interface Ethernet1
no ip address
shutdown
!
interface Serial0
ip unnumbered Ethernet0
appletalk cable-range 120-120 120.17
appletalk zone left
ipx network AD
clockrate 56000
!
interface Serial1
no ip address
shutdown
!
router igrp 100
network 172.16.0.0
!
no ip classless
!!
line con 0
line aux 0
line vty 0 4
login
!
end
Router_B#sh run
Building configuration...
Current configuration:
!
version 11.3
no service password-encryption
!
hostname Router_B
!
!
appletalk routing
ipx routing 0007.7816.fe54
!
interface Loopback0
ip address 172.17.1.1 255.255.255.0
!
interface Serial0
ip unnumbered Loopback0
no ip mroute-cache
appletalk cable-range 130-130 130.81
appletalk zone right
ipx network CAD
no fair-queue
!
interface Serial1
ip unnumbered Loopback0
appletalk cable-range 120-120 120.125
appletalk zone left
ipx network AD
!
interface Serial2
no ip address
shutdown
!
interface Serial3
no ip address
shutdown
!
interface TokenRing0
no ip address
shutdown
!
interface BRI0
no ip address
shutdown
!
router igrp 100
network 172.17.0.0
!
ip classless
!
!
!
!
!
line con 0
line aux 0
line vty 0 4
login
!
end
Router_A#sh run
Building configuration...
Current configuration:
!
version 11.3
no service password-encryption
!
hostname Router_A
!
!
appletalk routing
ipx routing 0010.7b15.bd41
!
interface Ethernet0/0
ip address 10.1.1.1 255.255.255.0
appletalk cable-range 106-110 106.17
appletalk zone left
ipx network BAD
!
interface Serial0/0
ip unnumbered Ethernet0/0
no ip mroute-cache
appletalk cable-range 130-130 130.37
appletalk zone right
ipx network CAD
clockrate 56000
!
interface TokenRing0/0
no ip address
shutdown
ring-speed 16
!
interface FastEthernet1/0
no ip address
shutdown
!
router igrp 100
network 10.0.0.0
!
ip classless
!!
line con 0
line aux 0
line vty 0 4
login
!
end
77. [RxNx] What routing protocols are configured?
a) EIGRP, IGRP, RIP
b) IGRP RTMP IPX NLSP
c) IPX RIP, IGRP, RTMP
d) EIGRP, RTMP, IPX RIP
e) IPX RIP, IGRP
Answer
c) IPX RIP, IGRP, RTMP
Appletalk s RTMP and Novell s IPX RIP are the default routing protocols.
Refer to the following routing tables of Router C:
Router_C#sh ip route
Codes: C - connected, S - static, I - IGRP,
R - RIP, M - mobile, B - BGP, D - EIGRP,
EX - EIGRP external, O - OSPF,
IA - OSPF inter area,
N1 - OSPF NSSA external type 1,
N2 - OSPF NSSA external type 2,
E1 - OSPF external type 1,
E2 - OSPF external type 2, E - EGP,
i - IS-IS, L1 - IS-IS level-1,
L2 - IS-IS level-2,
* - candidate default
U - per-user static route, o - ODR
Gateway of last resort is not set
I 10.0.0.0/8 [100/10576] via 172.17.1.1,
00:00:03, Serial0
172.16.0.0/24 is subnetted, 1 subnets
C 172.16.1.0 is directly connected,
Ethernet0
172.17.0.0/16 is variably subnetted,
2 subnets, 2 masks
I 172.17.1.0/32 [100/8976]
via 172.17.1.1,
00:00:03, Serial0
I 172.17.0.0/16 [100/8976]
via 172.17.1.1,
00:00:03, Serial0
Router_C#sh app route
Codes: R - RTMP derived, E - EIGRP derived,
C - connected, A - AURP
S - static P - proxy
4 routes in internet
The first zone listed for each entry is its
default (primary) zone.
C Net 100-105 directly connected,
Ethernet0, zone right
R Net 106-110 [2/G] via 120.125, 2 sec,
Serial0, zone left
C Net 120-120 directly connected,
Serial0, zone left
R Net 130-130 [1/G] via 120.125, 2 sec,
Serial0, zone right
Router_C#sh ipx route
Codes: C - Connected primary network,
c - Connected secondary network
S - Static, F - Floating static,
L - Local (internal), W - IPXWAN
R - RIP, E - EIGRP, N - NLSP,
X - External, A - Aggregate
s - seconds, u - uses
4 Total IPX routes. Up to 1 parallel
paths and 16 hops allowed.
No default route known.
C AD (HDLC), Se0
C DAD (NOVELL-ETHER), Et0
R BAD [13/02] via
AD.0007.7816.fe54, 28s, Se0
R CAD [07/01] via
AD.0007.7816.fe54, 28s, Se0
78. [RXNx] The Serial 0/0 IPX encapsulation of Router_A is:
a) Novell-ether
b) SAP
c) ARPA
d) SNAP
e) Can not be determined
f) HDLC
Answer
f) HDLC
The default encapsulation for a serial interface is HDLC.
Refer to the IPX routing table below:
Router_A#sh ipx route
%SYS-5-CONFIG_I: Configured from
console by console
Codes: C - Connected primary network,
c - Connected secondary network
S - Static, F - Floating static,
L - Local (internal), W - IPXWAN
R - RIP, E - EIGRP, N - NLSP,
X - External, A - Aggregate
s - seconds, u - uses, U - Per-user static
4 Total IPX routes. Up to 1 parallel
paths and 16 hops allowed.
No default route known.
C BAD (NOVELL-ETHER), Et0/0
C CAD (HDLC), Se0/0
R AD [07/01] via
CAD.0007.7816.fe54, 89s, Se0/0
R DAD [13/02] via
CAD.0007.7816.fe54, 89s, Se0/0
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