Ping - Command

Ping.....

Ping is one of the usefull and effective command in determine network test connectivity with another IP host. Typing PING followed by specific IP address at command prompt will immediately tell whether there is connectivity between your computer and the other host.

Ping test is often referred as testing the protocal stack, because the ping command moves from Layer 3 OSI model to Layer 2 and then Layer 1. Ping uses the ICMP protocol to check for connectivity.

Please note...ping will not always pinpoint the exact of the problem in the network, but it can help identify the source of the problem, one of important first step in network troubleshooting.

Ping command

There are also a number of options that you can use with the PING command. The available options are listed below.

-t Pings the specified host until stopped
-a Resolves addresses to hostnames
-n count Number of echo requests to send
-l size Send buffer size
-f Set Don’t Fragment flag in packet
-i TTL Time To Live
-v TOS Type of Service
-r count Record route for count hops
-s count Timestamp for count hops
-j host-list Loose source route along host-list
-k host-list Strict source route along host-list
-w timeout Timeout in milliseconds to wait for each reply

You can always find out more about a specific command by typing the command at the command prompt followed by “/?”.

Ping Indicators

A ping will yield to one several indicators for each ICMP echo that was sent. The most common indicators are :

!  - receipt of ICMP echo replay

.  - timed out while waiting for a replay

U- unreachable message was received

The "!" (exclamation mark) indicates that the ping completed successfully and verifies Layer 3 connectivity.

The "." (period) can indicate problems in the communication. It may indicate connectivity problem occurred somewhere along the path. It also may indicate a router along the path did not have a route to the destination and did not send an ICMP destination unreachable message. It also may indicate that ping was blocked by device security. 

The "U" indicates that a router along the path did not have a route to the destination address and responded with an ICMP unreachable message.

example :
Enter the ping loopback command with this syntax:

C:\>ping 127.0.0.1

The reply from this command would look something like this:

Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Reply from 127.0.0.1: bytes=32 time<1ms TTL=128
Ping statistics for 127.0.0.1:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 0ms, Maximum = 0ms, Average = 0ms

The result indicates that four test packets were sent - each 32 bytes in size - and were returned from host 127.0.0.1 in a time of less than 1 ms. TTL stands for Time to Live and defines the number of hops that the ping packet has remaining before it will be dropped.