table.
Content 3.3 Troubleshooting Routing Protocols 3.3.1 Routing protocol troubleshooting process All routing protocol troubleshooting should begin with a logical sequence, or process flow. This process flow is not a rigid outline for troubleshooting an internetwork. However, it is a foundation from which a network administrator can build a problem-solving process to suit a particular environment.
  1. When analyzing a network failure, make a clear problem statement.
  2. Gather the facts needed to help isolate possible causes.
  3. Consider possible problems based on the facts that have been gathered.
  4. Create an action plan based on the remaining potential problems.
  5. Implement the action plan, performing each step carefully while testing to see whether the symptom disappears.
  6. Analyze the results to determine whether the problem has been resolved. If it has, then the process is complete.
  7. If the problem has not been resolved, create an action plan based on the next most likely problem in the list. Return to Step 4, change one variable at a time, and repeat the process until the problem is solved.
  8. Once the actual cause of the problem is identified, try to solve it.
Cisco routers provide numerous integrated commands to assist in monitoring and troubleshooting an internetwork: Cisco IOS show commands are among the most important tools for understanding the status of a router, detecting neighboring routers, monitoring the network in general, and isolating problems in the network. EXEC debug commands can provide a wealth of information about interface traffic, internal error messages, protocol-specific diagnostic packets, and other useful troubleshooting data. Use debug commands to isolate problems, not to monitor normal network operation. Only use debug commands to look for specific types of traffic or problems. Before using the debug command, narrow the problems to a likely subset of causes. Use the show debugging command to view which debugging features are enabled. Web Links Troubleshooting EIGRP http://www.cisco.com/en/US/tech/ tk826/tk365/technologies_ tech_ note09186a0080094613.shtml
Content 3.3 Troubleshooting Routing Protocols 3.3.2 Troubleshooting RIP configuration The most common problem found in Routing Information Protocol (RIP) that prevents RIP routes from being advertised is the variable-length subnet mask (VLSM). This is because RIP Version 1 does not support VLSM. If the RIP routes are not being advertised, check the following: The show ip protocols command provides information about the parameters and current state of the active routing protocol process. RIP sends updates to the interfaces in the specified networks. If interface FastEthernet 0/1 was configured but the network was not added to RIP routing, no updates would be sent out or received from the interface. Use the debug ip rip EXEC command to display information on RIP routing transactions. The no debug ip rip, no debug all, or undebug all commands will turn off all debugging. Figure shows that the router being debugged has received an update from another router at source address 192.168.3.1. That router sent information about two destinations in the routing table update. The router being debugged also sent updates. Both routers broadcasted address 255.255.255.255 as the destination. The number in parentheses is the source address encapsulated into the IP header. An entry most likely caused by a malformed packet from the transmitter is shown in the following output: RIP: bad version 128 from 160.89.80.43 Web Links Missing RIP Routes? Popular Troubleshooting Techniques http://www.cisco.com/en/US/about/
ac123/ac114/ac173/ac169/about_
cisco_packet_enterprise_solution
09186a00800a3453.html
Content 3.3 Troubleshooting Routing Protocols 3.3.3 Troubleshooting IGRP configuration Interior Gateway Routing Protocol (IGRP) is an advanced distance vector routing protocol developed by Cisco in the middle 1980s. IGRP has several features that differentiate it from other distance vector routing protocols such as RIP. Use the router igrp autonomous-system command to enable the IGRP routing process: R1(config)#router igrp 100 Use the router configuration network network-number command to enable interfaces to participate in the IGRP update process: R1(config-router)#network 172.30.0.0
R1(config-router)#network 192.168.3.0 Verify IGRP configuration with the show running-configuration and show ip protocols commands: R1#show ip protocols Verify IGRP operation with the show ip route command: R1#show ip route If IGRP does not appear to be working correctly, check the following: To view IGRP debugging information, use the following commands: To turn off debugging, use the no debug ip igrp command. If a network becomes inaccessible, routers running IGRP send triggered updates to neighbors to inform them. A neighbor router will then respond with poison reverse updates and keep the suspect network in a holddown state for 280 seconds. Web Links IGRP http://www.cisco.com/en/US/tech/
tk365/tk352/technologies_tech_note
09186a0080093f0b.shtml
Content 3.3 Troubleshooting Routing Protocols 3.3.4 Troubleshooting EIGRP configuration Normal EIGRP operation is stable, efficient in bandwidth utilization, and relatively simple to monitor and troubleshoot. Use the router eigrp autonomous-system command to enable the EIGRP routing process: R1(config)#router eigrp 100 To exchange routing updates, each router in the EIGRP network must be configured with the same autonomous system number. Use the router configuration network network-number command to enable interfaces to participate in the EIGRP update process: R1(config-router)#network 172.30.0.0
R1(config-router)#network 192.168.3.0 Verify EIGRP configuration with the show running-configuration and show ip protocols commands: R1#show ip protocols