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

1 192.168.30.2 16 msec 16 msec *
Randy#
Possible responses when using traceroute (from most likely to least likely
response):
Response Description
* Timed out
U Port was unreachable
N Network was unreachable
P
Protocol is unreachable
!H Received but not forwarded…ACL is set
Another layer 3 tool you can use to look for clues is the sh ip route command.
Here you can determine if your router is advertising and receiving routes and if
they are correctly being advertised and received. Here is an example routing table
from Randy in our example:
Randy>sh 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 - EGP
i - 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
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>
If you feel you have your routing protocol correct but the routes are not showing
up in the ip routing table then clear them several times:
Randy#clear ip route *
Randy#clear ip route *
Randy#clear ip route *
Randy#
Then try to see if your routes are correct. You may even have to clear them on all
your routers. As a last resort take out your routing protocol and put it back in.
Don’t ask me why…sometimes that is all that is needed.
193