Chapter 13 Network Troubleshooting Troubleshooting problems in a

Chapter 13 Network Troubleshooting • Troubleshooting problems in a 5 router network

Sample LAB SETUP S 0 Console Cable S 1 199. 6. 13. 1 LAB B 201. 100. 11. 2 LAB C S 0 S 1 Console Cable S 1 199. 6. 13. 0 NW 255. 0 204. 7. 2 204. 7. 0 NW 255. 0 201. 100. 11. 0 NW 255. 0 S 0 199. 6. 13. 2 204. 7. 1 LAB D 210. 93. 105. 1 E 0 Console Cable 201. 100. 11. 1 Switch LAB A 210. 93. 105. 0 NW 255. 0 E 0 Console Cable 210. 93. 105. 2 LAB E

Layer 1 Errors • Broken cables • Disconnected cables • Cables connected to the wrong ports • Intermittent cable connection • Wrong Cables used for the task at hand. Must use rollovers, straight-through and cross-over cables properly • Transceiver problems • DCE cable problems • DTE cable problems • Devices turned off or unplugged

Layer 2 Errors • Improperly configured serial interfaces • Improperly configured Ethernet interfaces • Cables connected to the wrong ports • Improper encapsulation set (HDLC is the default for serial interfaces) • Improper clock rate settings on serial interfaces

Layer 3 Errors • Routing protocol not enabled • Wrong routing protocol enabled • Incorrect IP addresses • Incorrect subnet masks • Incorrect DNS to IP bindings

OSI Layer Troubleshooting START Layer 1 OK? NO Fix Layer 1 YES Layer 2 OK? NO Fix Layer 2 YES Layer 3 OK? NO Fix Layer 3 YES Layer 4 OK? NO Fix Layer 4 YES Layer 5 OK? NO Fix Layer 5 YES Layer 6 OK? NO Fix Layer 6 YES Layer 7 OK? YES STOP NO Fix Layer 7

START Collect all available information and analyze the symptoms of failure Localize the problem to within a single network segment, to a single complete module or unit, or to a single user Isolate the trouble to a specific hardware or software, within a unit, module, or user’s network account Locate and correct the specific problem Verify that the problem has been solved 5 - Step Troubleshooting Other problems? NO STOP YES