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The traceroute or trace command is used to show the complete route from a source to a destination. Trace
sends out probe packets one at a time to each router or switch in the path between the source and the
destination IP address entered. Traceroute displays the round-trip time for each packet sent to each upstream
router. Traceroute has really only two results, time exceeded or destination unreachable. Trace is used to
determine where a breakdown in a route may be occurring.
HereÇs an example of how trace is used: A network has four routers (A, B, C, and D). A trace command is
issued on router A to trace the route from itself to router D. A timing response comes back from router B, but
the next message indicates that router C is unreachable. You can be fairly certain that the problem lies
somewhere on the route between router B and router C.
Remember Like PING, trace has its own set of response codes, listed in Table 12-8, that you should know
for the CCNA exam.
Table 12-8: Trace Command Response Codes
Response Meaning
* timed out
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!H router received packet but did not forward it (usually due to an access list)
N network unreachable
P protocol unreachable
U port unreachable
Here are the results of a sample traceroute session in which all stations were reachable:
CCNA_4_DUMMIES#traceroute 192.5.5.1
Type escape sequence to abort.
Tracing the route to LAB-A (192.5.5.1)
1 LAB D (210.93.105.1) 4 msec 4 msec 4 msec
2 LAB C (204.204.7.1) 20 msec 32 msec 28 msec
3 LAB B (199.6.13.1) 44 msec 48 msec 44 msec
4 LAB A (201.100.11.1) 64 msec * 60 msec
Prep Test
1. Which of the following addresses is not a Data Link layer address?
A. MAC
B. Ethernet
C. IP
D. Physical
E. Burned in
2.
Who assigns each portion of the MAC address?
A. First 24 bits IEEE, last 24 bits the manufacturer
B. First 4 bytes IEEE, last 4 bytes the manufacturer
C. First 12 bits the manufacturer, last 36 bits IEEE
D. First 3 bytes Internic, last 3 bytes Cisco
3.
Looking at an IPX address of 5ca9.0000.f0d3.76be, which portion is the network address and which is
the node address?
A. 5ca9.0000 network; f0d3.76be node
B. 76be network; 5ca9.0000.f0d3 node
C. 5ca9 network; 0000.f0d3.76be node
D. 5ca9.0000.f0d3 network; 76be node
4.
What is the binary equivalent of the dot decimal IP address 156.162.179.181?
A. 10011100 10100010 10110011 10110101
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B. 10011101 10100010 10110011 10110101
C. 10011100 10100011 10110011 10110101
D. 10011100 10100010 10111011 1011001
5.
An IP address starting with a bit sequence in the first octet of 110 would fall into what IP address
Class?
A. Class D or E
B. Class C
C. Class B
D. Class A
6. Given a binary IP address of 11001110 10101111 10100010 00010010 and a dotted decimal subnet
mask of 255.255.255.0 what is the network ID?
A. 205.175.162.0
B. 206.159.162.0
C. 206.175.162.18
D. 206.175.162.0
7.
After entering the command show int e1 you read a line of output that reads ÝInternet address is
191.168.16.6/16Û. Which of the following is not true?
A. Your network number is 191.168.0.0
B. This is a Class B network
C. The netmask-format has been set to bit-count
D. You have configured 16 sub-interfaces on Ethernet port 1
8.
When issuing a PING command from a Telnet session, what response would you expect to receive if
the packetÇs TTL field was exceeded?
A. ! (exclamation point)
B. & (ampersand)
C. | (vertical bar)
D. . (period)
9.
What does the response ÝCÛ mean to a ping command?
A. CanÇt reach destination
B. Congestion-experienced
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C. Carrier loss
D. Consistent response
10.
When issuing a traceroute command what does the response Ý!HÛ mean?
A. Network unreachable
B. Protocol unreachable
C. Access list prevents forwarding
D. Timed out
Answers
1. C. An IP is a Network layer address. The remaining answers are all variations of the same thing and
as such are Data Link layer addresses. See ÝMAC addresses.Û
2.
A. The first 24 bits (3 bytes) are assigned by the IEEE to identify the manufacturer, who in turn adds
the last 24 bits (3 bytes) as a serial number for the network adapter. Review ÝMAC addresses.Û
3.
C. 5ca9 represents the network and 0000.f0d3.76be represents the node. Remember that leading zeros
on the beginning of the network portion are omitted. Take a look at ÝA Novell idea.Û
4.
A. No cheating and using your calculator for this one. Be sure you know how to compute this without
using a calculator. You will be called on to do this on the test. Check out ÝThinking in binary.Û
5.
B. Class C addresses use a three-bit identifier. Class B uses a two-bit (10), and Class A uses a single
one-bit value (set to 1). See ÝIP addresses.Û
6.
D. The network ID is 206.175.162.0, which is extracted because none of the last octetÇs bit are used.
Review ÝItÇs only a trial separation.Û
7.
D. You have not configured 16 sub-interfaces on Ethernet port 1. Review the configuration process
used in this chapter and practice it if you have access to a router. Look over ÝConfiguring an IP
address.Û
8.
B. The ampersand (&) character indicates the TTL value was exceeded. Check out ÝVerifying with
PING.Û
9.
B. The ÝCÛ character indicates that the PING packets experience congestion on the network. See
ÝVerifying with PING.Û
10.
C. This response indicates the access list entries have prevented the trace packets from being
forwarded. Review ÝVerifying with traceroute.Û
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Chapter 13: Subnetting
Exam Objectives
" Creating subnet masks
"
Applying subnetting
If you carefully consider the two exam objectives for this chapter, you discover that theyÇre really just pieces [ Pobierz caÅ‚ość w formacie PDF ]