ADV. PING

ADV. PING

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Testing Communication with Another Computer by Using Ping

Sending a small text packet on a round-trip is called pinging, and you can use Windows' built-in Ping program to send one. (Imagine that your computer sends the message "ping" and the other computer replies "pong.") To run Ping, open a Command Prompt window by choosing Start | All Programs | Accessories | Command Prompt and type the Ping command, as follows:

ping system

Replace system with either the numeric IP address or the host name of the computer you want to ping. Choose any Internet host computer that you're sure is online, such as your ISP's mail server. Then press ENTER.

tip To see a listing of all the command-line options for the Ping program, type ping /? at the DOS prompt.

For example, you can ping the Yahoo! Web server (a Web search engine and directory) by typing

ping www.yahoo.com

Ping sends out four test packets (pings) and reports how long the packets take to get to the Internet Gurus computer and back to yours, like this:

Pinging net.gurus.com [208.31.42.79] with 32 bytes of data:

Reply from 208.31.42.79: bytes=32 time=204ms TTL=248

Reply from 208.31.42.79: bytes=32 time=220ms TTL=248

Reply from 208.31.42.79: bytes=32 time=200ms TTL=248

Reply from 208.31.42.79: bytes=32 time=210ms TTL=248

Ping statistics for 208.31.42.79:

Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),

Approximate round trip times in milli-seconds:

Minimum = 200ms, Maximum = 220ms, Average = 208ms

For each packet, you see both how long the round-trip takes in milliseconds and summary information about all four packets' trips. If ping doesn't receive the response it is waiting for within a time limit, you see an error message.

Ping has a number of options, which are listed in Table 22-2. Ping has other arcane options, not listed here.

tip First try Ping with a numeric IP address (for example, 216.32.74.50 for a Yahoo! Web server, or 208.31.42.79 for our Web server), to see whether packets get out to the Internet and back. Then try Ping with a host name, to see whether you successfully contact your DNS to convert the name into an IP address. If the first test works and the second doesn't (failing with an "Unable to resolve target system name" error), your connection isn't set up properly to contact a DNS.

Option 	Description
-a 	Reports numeric addresses rather than host names.
-f 	Specifies that packets contain a Do Not Fragment flag, so packets aren\'t fragmented en route. (Useful to test very slow dial-up connections.)
-i ttl 	Specifies the Time To Live for the packets (how many times the packet can be passed from one computer to another while in transit on the network).
-n n 	Specifies to send n pings. (The default is four.)
-r n 	Specifies the outgoing and returning packets should record the first n hosts on the route they take, using the Return Route field; n is a number from 1 to 9.
-t 	Specifies to continue pinging until you interrupt it. (Otherwise, it pings four times.)
-w n 	Specifies a time-out of n milliseconds for each packet.