Learning by Doing: CISCO Certified Network ... - SCN Research

Gateway of last resort is not set
C 192.168.30.0/24 is directly connected, Serial0/0
R 192.168.4.0/24 [120/1] via 192.168.30.2, 00:00:07, Serial0/0
C 192.168.3.0/24 is directly connected, Ethernet0/0
Randy>
We see our directly connected routes and the one learned via our routing protocol.
Getting stuck? Try using this command at the privileged prompt:clear ip route *
several times on each router to “restart” the routing process (clears the tables,
sends updates, receives updates, and re-creates the ip routing table). This is a
really good command to remember and keep in your “arsenal.”
13. Let’s watch ICMP packets as they pass from one router to another. Turn on
debug, then ping and trace route from the workstation to generate icmp “traffic.”
Side note: debug can really chew up resources. Be sure to use just enough debug
to get the job done, then turn off debug. Notice how we had to change user
modes:
Randy#debug ip icmp
(use “undebug ip icmp” or “undebug all” to
turn off)
You should see: {This is what I sent}
Pinging 192.168.4.2 with 32 bytes of data:
Reply from 192.168.4.2: bytes=32 time=23ms TTL=126
Reply from 192.168.4.2: bytes=32 time=20ms TTL=126
Reply from 192.168.4.2: bytes=32 time=20ms TTL=126
Reply from 192.168.4.2: bytes=32 time=20ms TTL=126
Ping statistics for 192.168.4.2:
Packets: Sent = 4, Received = 4, Lost = 0 (0% loss),
Approximate round trip times in milli-seconds:
Minimum = 20ms, Maximum = 23ms, Average = 20ms
C:\WINDOWS\Desktop>tracert 192.168.4.2
Tracing route to STAR10616119 [192.168.4.2]
over a maximum of 30 hops:
1 2 ms 1 ms 1 ms 192.168.3.1
2 25 ms 25 ms 25 ms 192.168.30.2
3 30 ms 30 ms 30 ms STAR10616119 [192.168.4.2]
Trace complete.
C:\WINDOWS\Desktop>
You should see on RouterA:
Randy#debug ip icmp
ICMP packet debugging is on
Randy#
01:02:29: ICMP: time exceeded (time to live) sent to 192.168.3.2 (dest
was 192.168.4.2)
01:02:29: ICMP: time exceeded (time to live) sent to 192.168.3.2 (dest
was 192.168.4.2)
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