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Passing Cisco's CCNA and CCNP: Ping And Extended Ping |
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I often tell CCNA and CCNP candidates that you do your best
learning when you screw something up. I often get a funny
look right after I say that, but the only way to develop your
Cisco troubleshooting skills - the skills you'll need to pass
your Intro, ICND, and CCNP exams - is by actually fixing configurations.
Since your employer will take a dim view of you practicing
these skills on his or her network, you better do so on your
home lab!
Three essential tools for networking and CCNA/CCNP exam success
are ping, extended ping, and traceroute. Today we're going
to take a look at the ping that we're used to using for LAN
issues, and the extended ping.
We're all familiar with "basic" ping, where you
use the ping command followed by the IP address you want to
confirm IP connectivity with. When you've got connectivity,
you will see five exclamation points, as seen here:
R1#ping 172.12.123.2
Type escape sequence to abort.
Sending 5, 100-byte ICMP Echos to 172.12.123.2, timeout is
2 seconds:
!!!!!
Success rate is 100 percent (5/5), round-trip min/avg/max
= 68/68/72 ms
The default source IP address for ping is the IP address
closest to the destination IP address. Other defaults - five
ICMP packets will be sent (that's why you see five exclamation
points), and they're sent two seconds apart.
That's fine for many basic situations, but as you progress
through your networking career and most advanced scenarios
in your CCNA / CCNP studies, you will want to change some
of these defaults. What could you do if you wanted to send
10,000 pings? What if you needed your router's loopback address
to be the source IP address for the pings? What if you wanted
to send them five seconds apart, instead of two?
That's where extended ping comes in. To use extended ping,
just type "ping" and hit enter. (Note that you cannot
use extended ping in user exec mode - you must be in enable
mode to do so.)
R1>ping
% Incomplete command.
"incomplete command" indicates that the router
is waiting for an IP address; you can't use extended ping
in user exec mode.
R1>enable
R1#ping
Protocol [ip]:
Target IP address: 172.16.123.1
Repeat count [5]: 1000
Datagram size [100]:
Timeout in seconds [2]:
Extended commands [n]: y
Source address or interface: loopback0
Type of service [0]:
Set DF bit in IP header? [no]:
Validate reply data? [no]:
Data pattern [0xABCD]:
Loose, Strict, Record, Timestamp, Verbose[none]:
Sweep range of sizes [n]:
Type escape sequence to abort.
Sending 1000, 100-byte ICMP Echos to 172.16.123.1, timeout
is 2 seconds:
Packet sent with a source address of 1.1.1.1
.......................................
In this example, I sent 1000 ICMP packets to an address that
doesn't exist, so I am getting periods instead of exclamation
points. This illustration shows you the many options you have
with extended ping.
Now that I've sent those 1000 pings, let's say that I want
to stop that process. At the beginning of the basic ping output,
you see this phrase:
Type escape sequence to abort.
This escape sequence works for ping, extended ping, and traceroute.
Funny thing, though - Cisco doesn't tell you what the escape
sequence is! One day, this will really come in handy. The
escape sequence is , TWICE in rapid succession.
After I used it in this example, the pings stopped and I
got this message:
Success rate is 0 percent (0/192)
The ping stopped after 192 ICMP packets were sent.
This keystroke takes a little practice, so practice it in
your home lab. Knowing how to use extended ping will really
come in handy on your CCNA and CCNP exams as well as your
real-life networking job, and knowing how to stop an extended
ping will as well!
About the Author:
Chris Bryant, CCIE #12933, is the owner of The Bryant Advantage,
home of free CCNA and CCNP tutorials, The Ultimate CCNA Study
Package, and Ultimate CCNP Study Packages. For a FREE copy
of his latest e-books, “How To Pass The CCNA” and
“How To Pass The CCNP”, visit the website and download
your free copies. You can also get FREE CCNA and CCNP exam
questions every day! Pass the CCNA exam with The Bryant Advantage!
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