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TCP/IP Router Diagnostic Tools
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By understanding exactly how each of these utilities works, the informa-
tion provided by them can be invaluable. By using both tools, you can isolate
a router that has lost its default gateway (gateway of last resort). The fol-
lowing command line output indicates that a router is not reachable using
the
ping
command. The
traceroute
command indicates that there is a
route to the router, but the requests are timing out. Figure 6.3 depicts the net-
work topology.
F I G U R E 6 . 3
Using
ping
and
traceroute
to isolate a router with no default network
The first command--
ping--
fails. Figure 6.4 represents what happened.
Five individual probes were sent to Router C and none of them returned, so
the machine is unreachable.
F I G U R E 6 . 4
The ping utility indicates that Router C is unreachable
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