Cisco Activity
Task 3: Interpreting Debug Output.
Note: If you already configured IP addressing on R1, please remove all the interface commands now before proceeding. Furthermore, R2 and R3 should be configured through the end of “Task 2: Basic Router Configuration”.
Step 1 – On R1 from privileged EXEC mode, enter the debug ip routing command.
R1# debug ip routing.
IP routing debugging is on.
The debug ip routing command will show when routes are added, modified and deleted from the routing table. For example, every time you successfully configure and activate an interface, Cisco IOS adds a route to the routing table. We can verify this by observing output from the debug ip routing command.
Step 2 – Enter interface configuration mode for R1’s LAN interface.
R1#configure terminal.
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)# interface fastethernet 0/0
Configure the ip address as specified in the Topology Diagram.
R1(config-if)# ip address 172.16.3.1 255.255.255.0. is_up: 0 state: 6 sub state: 1 line: 1 has_route: False
As soon as you press the enter key, Cisco IOS debug output informs you that there is now a route, but its state is “False”. In other words, the route has not yet been added to the routing table. Why did this occur and what steps should be taken to insure the route is entered into the routing table?
No shut down to int
Step 3 Enter the command necessary to install the route in the routing table.
If you are not sure what the command is, review the discussion in Section 2.2: Directly Connected Networks.
After you enter the correct command, you should see debug output. Your output may be slightly different. is_up: 1 state: 4 sub state: 1 line: 1 has_route: False
RT: add 172.16.3.0/24 via 0.0.0.0, connected metric [0/0]
RT: NET-RED 172.16.3.0/24
RT: NET-RED queued, Queue size 1
RT: interface FastEthernet0/0 added to routing table
%LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up is_up: 1 state: 4 sub state:
Note: If you already configured IP addressing on R1, please remove all the interface commands now before proceeding. Furthermore, R2 and R3 should be configured through the end of “Task 2: Basic Router Configuration”.
Step 1 – On R1 from privileged EXEC mode, enter the debug ip routing command.
R1# debug ip routing.
IP routing debugging is on.
The debug ip routing command will show when routes are added, modified and deleted from the routing table. For example, every time you successfully configure and activate an interface, Cisco IOS adds a route to the routing table. We can verify this by observing output from the debug ip routing command.
Step 2 – Enter interface configuration mode for R1’s LAN interface.
R1#configure terminal.
Enter configuration commands, one per line. End with CNTL/Z.
R1(config)# interface fastethernet 0/0
Configure the ip address as specified in the Topology Diagram.
R1(config-if)# ip address 172.16.3.1 255.255.255.0. is_up: 0 state: 6 sub state: 1 line: 1 has_route: False
As soon as you press the enter key, Cisco IOS debug output informs you that there is now a route, but its state is “False”. In other words, the route has not yet been added to the routing table. Why did this occur and what steps should be taken to insure the route is entered into the routing table?
No shut down to int
Step 3 Enter the command necessary to install the route in the routing table.
If you are not sure what the command is, review the discussion in Section 2.2: Directly Connected Networks.
After you enter the correct command, you should see debug output. Your output may be slightly different. is_up: 1 state: 4 sub state: 1 line: 1 has_route: False
RT: add 172.16.3.0/24 via 0.0.0.0, connected metric [0/0]
RT: NET-RED 172.16.3.0/24
RT: NET-RED queued, Queue size 1
RT: interface FastEthernet0/0 added to routing table
%LINK-3-UPDOWN: Interface FastEthernet0/0, changed state to up is_up: 1 state: 4 sub state: