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Identifying and Resolving Generic Router Problems
257
code specifies that the host is not reachable. The ping command may be
issued, but it will render the same information--host unreachable.
What other tool might be used to aid in defining the border of dysfunctionality?
There are a couple of different directions that may be taken. One method is to try
to FTP a file to hosts that do not reside on the 172.16.10.0/24 network. Another
consists of running a traceroute to see where the path to Host A is failing.
Let's try the latter. Following are the results of a traceroute to Host A:
C:\WINDOWS>tracert 172.16.10.2
Tracing route to 172.16.10.2 over a maximum of 30 hops
1 5 ms 2 ms 4 ms 172.16.60.1
2 172.16.60.1 reports: Destination host unreachable.
Trace complete.
These results indicate that Router C does not have a route to Host A. This
allows you to draw the line of dysfunctionality to the boundary between
Router C and Router B.
To further troubleshoot this problem, diagnostics must be executed from
Router C. Let's bring up a console on Router C. The first command that
should be issued is a show ip route. The results are as follows:
Router_C#show ip route
Codes: C - connected, S - static, I - IGRP, R - RIP, M -
mobile, B ­ BGP D - EIGRP, EX - EIGRP external, O - OSPF,
IA - OSPF inter area N1 - OSPF NSSA external type 1, N2 -
OSPF NSSA external type 2 E1 - OSPF external type 1, E2 -
OSPF external type 2, E - EGPi - IS-IS, L1 - IS-IS level-
1, L2 - IS-IS level-2, * - candidate default U - per-user
static route, o - ODR
Gateway of last resort is not set
172.16.0.0/24 is subnetted, 2 subnets
C 172.16.60.0 is directly connected, Ethernet0/1
C 172.16.50.0 is directly connected, Ethernet0/0
Router_C#
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