CN – Lab Exercise 2

Objective 

·   Learn to use the TCP/IP Packet Internet Groper (ping) command from a workstation.

·   Learn to use the Traceroute (tracert) command from a workstation.

·   Observe name resolution occurrences using WINS and/or DNS servers.

Background

This lab assumes the use of any version of Windows. This is a non-destructive lab and can be done on any machine without concern of changing the system configuration.  Ideally, this lab is performed in a LAN environment that connects to the Internet. It can be done from a single remote connection via a modem or DSL-type connection. The student will need the IP addresses that were recorded in the previous lab. The instructor might also furnish additional IP addresses.

Note: Ping has been used in many DOS attacks and many school network administrators have turned off ping, echo reply, from the border routers. If the network administrator has turned off echo reply then it is possible for a remote host to appear to be offline when the network is operational.

DEFINITION

What is Ping?

A ultility to determine whether a specific IP address is accessible

What is Tracert?

Traceroute is a network diagnostic tool used to track the pathway taken by a packet on an IP network from source to destination. Traceroute also records the time taken for each hop the packet makes during its route to the destination

Step 1 Establish and verify connectivity to the Internet

This ensures the computer has an IP address.

Step 2 Access the command prompt

Use the Start menu to open the Command Prompt window. Press Start, type Run then type cmd which stands as Command Prompt

Step 3 ping the IP address of another computer

In the window, type ping, a space, and the IP address of a computer recorded in the previous lab. 

Ping uses the ICMP echo request and echo reply feature to test physical connectivity. Since ping reports on four attempts, it gives an indication of the reliability of the connection. Look over the results and verify that the ping was successful. Is the ping successful?

If not, perform appropriate troubleshooting. Yes, the ping is successful

If a second networked computer is available, try to ping the IP address of the second machine.

Note the results.

Step 4 ping the IP address of the default gateway

Try to ping the IP address of the default gateway if one was listed in the last exercise. If the ping is successful, it means there is physical connectivity to the router on the local network and probably the rest of the world.

Step 5 ping the IP address of a DHCP or DNS servers

Try to ping the IP address of any DHCP and/or DNS servers listed in the last exercise. If this works for both server and they are not in the network, what does this indicate?

Both address are reachable from any workstation

Was the ping successful?Sometime it may successful, sometime not.

If not, perform appropriate troubleshooting.

Step 6 ping the Loopback IP address of this computer

Type the following command: ping 127.0.0.1 

The 127.0.0.0 network is reserved for loopback testing. If the ping is successful, then TCP/IP is  properly installed and functioning on this computer.

Was the ping successful? Yes, unless the NIC is broken down

If not, perform appropriate troubleshooting.

Step 7 ping the hostname of another computer

Try to ping the hostname of the computer that was recorded in the previous lab. 

If the ping is successful, it means the computer was able to resolve the host name to an IP address. Without name resolution, the ping would have failed because TCP/IP only understands valid IP addresses, not names.

If the ping was successful, it means that connectivity and discovery of IP addresses can be done with only a hostname. In fact, this is how many early networks communicated. If successful, then ping a hostname also shows that there is probably a WINS server working on the network. WINS servers or a local “lmhosts” file resolve computer host names to IP addresses. If the ping fails, then chances are there is no NetBIOS name to IP addresses resolution running.

Note: It would not be uncommon for a Windows Vista or 7 networks to not support this feature.

It is an old technology and often unnecessary.

Step 8 ping the Google web site

Type the following command: ping www.google.com

The first output line shows the Fully Qualified Domain Name (FQDN) followed by the IP address. A

Domain Name Service (DNS) server somewhere in the network was able to resolve the name to an IP address. DNS servers resolve domain names, not hostnames, to IP addresses. 

Without this name resolution, the ping would have failed because TCP/IP only understands valid IP addresses. It would not be possible to use the web browser without this name resolution.

With DNS, connectivity to computers on the Internet can be verified using a familiar web address, or domain name, without having to know the actual IP address. If the nearest DNS server does not know the IP address, the server asks a DNS server higher in the Internet structure.

Step 9 ping the Microsoft web site

Type the following command: ping www.microsoft.com

Notice that the DNS server was able to resolve the name to an IP address, but there is no response.

Some Microsoft routers are configured to ignore ping requests. This is a frequently implemented security measure.

ping some other domain names and record the results. For example, ping www.msn.de 

the ping should be successfull but Request time out.

Step 10 Trace the route to the Yahoo web site

Type tracert www.yahoo.com and press Enter.

tracert is TCP/IP abbreviation for trace route. The preceding figure shows the successful result when running tracert.

Each router represents a point where one network connects to another network and the packet was forwarded through.

Explain tracert and differentiate it with ping.

Ping is a ultility to determine whether a specific IP address is accessible while tracert is a network diagnostic tool used to track the pathway taken by a packet on an IP network from source to destination. Traceroute also records the time taken for each hop the packet makes during its route to the destination

 Step 11 Trace other IP addresses or domain names

Try tracert on other domain names or IP addresses and record the results. An example is

tracert www.msn.de. 

Step 12 Trace a local host name or IP address

Try using the tracert command with a local host name or IP address. It should not take long because the trace does not pass through any routers.

 

Reflection 

If the above steps are successful and ping or tracert can verify connectivity with an Internet Web site, what does this indicate about the computer configuration and about routers between the computer and the web site? What, if anything, is the default gateway doing? 

If all of the above steps are successful snd ping or tracert can verify connectivity with an Internet Web site and everything should be working properly, its mean that ISP connection is working and the IP config is correct which enable them to be access or connect to each other. And default gateways is the device that passess traffic from local subnet to another device subnet.  The default gateway often connects a local network to the Internet, although internal gateways for local networks also exist.