IP Troubleshooting Small Group Exercise
This is a small group activity consisting of an IP troubleshooting exercise consisting of five scenario based questions. The exercise begins with a review of a recommend IP troubleshooting procedure and continues with five scenario based questions.
Simplified IP Troubleshooting Procedures:
* Verify layer-1 and layer-2
* Physical connectivity to the host to connected. Ethernet connection should indicate electrical connectivity with some type of LED indicator light.
* Verify OS detecting network interface correctly by verifying drivers installed correctly and OS display the interface as “connected”
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* Verify layer-1 / physical connectivity to the host to connected.
* Ethernet connection should indicate electrical connectivity with some type of LED indicator light.
* Serial connections will rely on CSU/DSUs for layer-1 and layer-2 connectivity.
* Verify layer-2 connectivity. This procedure will change depending on the medium being utilized. Frame-Relay, serial, and Ethernet all have different methods.
* All mediums will show a “up/up” with the show interface “interface” if both layer-1 and layer-2 are functioning correctly
* Verify layer-3 connectivity
* Verify IP address assignment with the “show ip interface brief” command
* IP address and mask correctly assigned to the various interfaces?
* Does the router make use of a default gateway?
* Attempt to ping default gateway
* If successful router has layer-3 connectivity to directly connected network between router and default gateway
* If unsuccessful attempt to ping other host on directly connected IP subnets
* Directly connected networks connectivity
* If router is having issues with pinging hosts on directly connected network, verify ARP resolution by using the command ”show arp” command. This command displays all the dynamic ARP resolutions. If no ARP entries present the router may have hidden layer-2 issues.
* Verify IP connectivity to remote networks
* Review IP routing table “show ip route”
* Inspect static routes and configuration
* Inspect dynamic protocols and configuration
* Verify IPv4 routing not disabled with the “no ip routing” command
Scenario questions on pages that follow
Scenario 1: End user complains of lack of connectivity to any resource not on the directly connected network. The host cannot ping its default gateway. The output of the “ipconfig /all” command is below. Also the IP address assigned to the router for that segment is also displayed below. What do you think the problem is with the configuration of this host?
PC “ipconfig /all” output (summarized)
Ethernet adapter Local Area Connection:
Physical Address. . . . . . . . . : 00-AB-C5-00-00-00
DHCP Enabled. . . . . . . . . . . : No
IPv4 Address. . . . . . . . . . . : 192.168.40.9
Subnet Mask . . . . . . . . . . . : 255.255.255.128
Default Gateway . . . . . . . . . : 192.168.40.254
DNS Servers . . . . . . . . . . . : 220.127.116.11
Router “show ip interface brief”
Router# show ip interface brief
Interface IP-Address OK? Method Status Protocol
GigabitEthernet0/0 192.168.40.254 YES NVRAM up up
Not in the correct network. The net IP would be 192.168.40.0 then first and last would be 192.168.40.1 thru 192.168.40.126 with 126 usable ip’s.
Scenario 2: One user complains of lack of connectivity to certain resources outside of their directly connected network. The...