Troubleshoot IPv4 Static and Default Route Configuration
Network Changes
Networks fail for a number of reasons:
•An interface can fail
•A service provider drops a connection
•Links can become oversaturated
•An administrator may enter a wrong configuration.
Network administrators are responsible for pinpointing and solving the problem.
To efficiently find and solve these issues, it is advantageous to be intimately familiar with tools to help isolate routing problems quickly.
| Command | Description |
| ping | •Verify Layer 3 connectivity to destination. •Extended pings provide additional options. |
| traceroute | •Verify path to destination network. •It uses ICMP echo reply messages to determine the hops to the destination. |
| show ip route | •Displays the routing table. •Used to verify route entries for destination IP addresses. |
| show ip interface brief | •Displays the status of device interfaces. •Used to verify the operational status and IP address of an interface. |
| show cdp neighbors | •Displays a list of directly connected Cisco devices. •Also used to validate Layer 1 and 2 connectivity. |
R2# show ip route | begin Gateway
Gateway of last resort is not set
172.16.0.0/16 is variably subnetted, 5 subnets, 2 masks
C 172.16.1.0/24 is directly connected, GigabitEthernet0/0/0
L 172.16.1.1/32 is directly connected, GigabitEthernet0/0/0
C 172.16.2.0/24 is directly connected, Serial0/l/0
L 172.16.2.2/32 is directly connected, Serial0/l/0
S 172.16.3.0/24 [1/0] via 192.168.1.1
192.168.1.0/24 is variably subnetted, 2 subnets, 2 masks
C 192.168.1.0/24 is directly connected, Serial0/1/1
L 192.168.1.2/32 is directly connected, Serial0/1/1
S 192.168.2.0/24 [1/0] via 192.168.1.1
R2#
