Use the
traceroute
Cisco IOS command
from source router to destination router.
Use the
tracert
Windows OS command
from source workstation to destination router.
Use the
show ip route
command to
display the router's routing table.
Verify that the network-layer
between source, destination and each router along the way is
working
properly.
Retrieve information to evaluate the
end-to-end path reliability.
Determine delays at each point over
the path and whether the host can be reached.
Background:
In this lab you will use the IOS traceroute
command. The traceroute
command uses ICMP packets and the error message generated by routers
when the packet exceeds its Time To Live (TTL). When you initiate
the trace
command to a target host the router sends an ICMP echo-request
packet with the TTL set to one (1). The first router in the path to
the target host receives the ICMP echo-request packet and sets the
TTL to zero (0). The first router then sends an ICMP Time-exceeded
message back to the source. The source router then sends an ICMP
echo-request packet with the TTL set to two (2). The first router
receives the ICMP echo-request and sets the TTL to one (1) and
(delete enter) sends it to the next router in the path to the target
host. The second router receives the ICMP echo-request and sets the
TTL to zero (0) then sends an ICMP Ttime-exceeded message back to
the source. The source then sends an ICMP echo-request with a TTL
set to 3. This cycle continues until an ICMP echo-reply is received
from the target host or until a ICMP destination-unreachable message
is received. This allows you to determine the last router to be
reached in the path to the target host. This is a troubleshooting
technique called fault isolation.
Tools
/ Preparation:
Prior to starting the lab you will need to
connect a PC workstation with HyperTerminal to a router using the
routers console Interface with a roll-over cable. This lab should be
done at the router console station. You may want to review Chapter 13 in
the Cisco Networking Academy First-Year Companion Guide and review
Semester 2 Online Chapter 4 prior to starting this lab. Work
individually or in teams. Be familiar with the following commands:
traceroute ip xxx.xxx.xxx.xxx
-
(Where xxx.xxx.xxx.xxx is the IP address of the host you want to
trace). The
ip
after the command is the default and may be
omitted.
traceroute hostname
(Where
host name is a name that can be resolved to an IP address).
traceroute is a Cisco IOS
command.
tracert xxx.xxx.xxx.xxx -
(Where xxx.xxx.xxx.xxx is the IP address of the host you want to
trace). tracert is a Windows 95/98 or NT command.
tracert hostname -
(Where
host name is a name that can be resolved to an IP address).
show ip route -
This will
show you the IP routing table - the directions that the router
uses to determine how it will direct traffic across the
network.
Resources Required:
PC with
monitor, keyboard, mouse, and power cords
etc.
Windows operating system (Win 95, 98, NT or 2000)
installed on PC
Connect to the router
and login. Enter the password
cisco
if prompted.
1a. What prompt did the router display?
1b. What does it mean?
Step 2 - Enter
trace
(abbreviated form of
traceroute).
Task:
Entertrace
at the router
prompt.
2. What did the router respond with?
Note: After
entering the trace command, you need to hit <enter> twice to
return to the command line.
Step 3 - Enter
trace ?
Task:
Enter
trace ?
at the router
prompt.
3. What did the router respond
with?
Step 4 - Get help with trace ip command.
Task:
Enter
trace ip ?
at the
router prompt.
4. What did the router respond
with?
Step 5 - Trace route from end router to end router.
Task:
Entertrace ip xxx.xxx.xxx.xxx
where
xxx.xxx.xxx.xxx is the IP address of the target destination.
Note: You will want to do
this lab using one of the end routers and trace IP
to the other
end router. (note: ip is the default) Explanation:
Trace command is
the ideal tool for finding where data is being sent in your network.
5. List the host name and
IP address of the routers that the ICMP packet was routed through.
Host
Name
IP
Address
Step 6 - Trace the route to all other routers on your network.
Task:
Repeat Step 5 with all other
routers on your network.
Step 7 - Use
tracert
from a MS-DOS command prompt.
Task:
From the console workstation click
on Start/Programs/MS DOS Command Prompt. An MS-DOS Command Prompt window will open up. Enter
tracert
and the same IP address that you used in step 5.
Explanation: By using the MS-DOS window
you will be using the TCP/IP stack of the workstation to begin the trace to the destination. The first
hop will be your default gateway or the near side router
interface on the LAN that the workstation is connected to.
6a. List the host name and
IP address of the router that the ICMP packet was routed through.
Host
Name
IP
Address
6b. Why is there one more entry in the output of the
tracert
command when you trace from the computer command prompt to the
target host?
Step
8 – Trace a route over the Internet.
Task:
From
a Windows 95/98 or NT workstation that has Internet access click on
Start/Programs/MS DOS Command Prompt.An MS-DOS Command Prompt window will open up. Enter tracert
www.cisco.com.
7a. What is the IP address
of www.cisco.com?
7b. How many hops did it
take to get to
www.cisco.com? If a packet passes through a
router it is considered one
(1) hop and the TTL of the packet is decremented by one (1).
Step 9
- View the routing table of the router.
Task:
From the router prompt entershow
ip route. Explanation: This will show you
the router's routing table.
8.
List the IP network number addresses
that are directly connect to you.