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Chapter 4
Cisco's Diagnostic Commands
ping Commands
The previous tools are in-depth tools used for problems that require very
high granularity. This means that these tools are used to provide very
detailed and specific information at a very low-level view. The ping com-
mand is a high-level simple tool. It is used to test for reachability and con-
nectivity throughout a network.
This tool can be used to effectively isolate network problems. If certain
machines on a network respond to the pings when others do not, this directs your
efforts to focus more on the individual machines that are not responding.
Cisco provides two implementations of the ping command: the user and
privileged levels. ping works for the following protocols on both levels:
IP
IPX
AppleTalk
CLNS
Apollo
VINES
DECnet
XNS
User EXEC Mode
The user mode for ping is restricted. Only the non-verbose method is
allowed for the user level. We now discuss the user mode for IP, IPX,
and AppleTalk.
IP
IP ping
uses ICMP as the protocol to provide connectivity and reachability
messages. It works on a simple principle: an ICMP echo message is sent to
the specified IP address. If the address is reachable, the receiving station
sends an ICMP echo-reply message back to the sending station.
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