Cisco Networking/CCENT/Troubleshooting

This lesson covers troubleshooting.

Objectives and Skills
Objectives and skills for the troubleshooting portion of Cisco CCENT certification include:
 * Troubleshoot and correct common problems associated with IP addressing and host configurations
 * Troubleshoot and resolve VLAN problems
 * Identify that VLANs are configured
 * Verify port membership is correct
 * Correct IP address is configured
 * Troubleshoot and resolve trunking problems on Cisco switches
 * Verify correct trunk states
 * Verify correct encapsulation is configured
 * Correct VLANs are allowed
 * Troubleshoot and resolve ACL issues
 * Verify statistics
 * Verify permitted networks
 * Verify direction
 * Interface
 * Troubleshoot and resolve Layer 1 problems
 * Framing
 * CRC
 * Runts
 * Giants
 * Dropped Packets
 * Late Collisions
 * Input/Output errors

Readings

 * 1)  Troubleshooting
 * 2) Cisco: Troubleshooting Ethernet
 * 3) Cisco: Troubleshooting Tools

Multimedia

 * 1) YouTube: The Network Troubleshooting Process - CompTIA Network+ N10-005: 1.8
 * 2) YouTube: Switch and Routing Diagnostics - CompTIA Network+ N10-005: 2.1
 * 3) YouTube: Troubleshooting Switch Loops - CompTIA Network+ N10-005: 2.5
 * 4) YouTube: Troubleshooting Network Cabling - CompTIA Network+ N10-005: 2.5
 * 5) YouTube: Troubleshooting Port Configuration - CompTIA Network+ N10-005: 2.5
 * 6) YouTube: Troubleshooting VLAN Assignments - CompTIA Network+ N10-005: 2.5
 * 7) YouTube: Troubleshooting Bad Fiber Modules - CompTIA Network+ N10-005: 2.5
 * 8) YouTube: Troubleshooting Mismatched MTUs - CompTIA Network+ N10-005: 2.5
 * 9) YouTube: Troubleshooting Power Failures - CompTIA Network+ N10-005: 2.5
 * 10) YouTube: Troubleshooting Routing - CompTIA Network+ N10-005: 2.5
 * 11) YouTube: Troubleshooting Subnet Masks and Gateways - CompTIA Network+ N10-005: 2.5
 * 12) YouTube: Troubleshooting Duplicate IP Addresses - CompTIA Network+ N10-005: 2.5
 * 13) YouTube:  Troubleshooting DNS - CompTIA Network+ N10-005: 2.5
 * 14) YouTube: Cisco Troubleshooting Exercise

show interfaces
To display statistics for all interfaces configured on the router or access server, use the show interfaces command in privileged EXEC mode. show interfaces

Review

 * 1) Review ../Remote Management
 * 2) Review ../Remote Management
 * 3) Review ../Static Routing
 * 4) Review ../Switching
 * 5) Review ../IOS Basics
 * 6) Review ../IOS Basics
 * 7) Review ../Remote Management
 * 8) Review ../Static_Routing
 * 9) Review ../Remote Management

VLANs

 * 1) Review ../VLANs
 * 2) Review ../VLANs
 * 3) Review ../VLANs

Access Control Lists

 * 1) Review ../Access Control Lists
 * 2) Review ../Access Control Lists
 * 3) Review ../Remote Management

Layer 1 Problems

 * 1) Review
 * 2) Review ../Static Routing

Activities

 * 1) Troubleshoot and correct common problems associated with IP addressing and host configurations.Cisco CCENT 2 Routers.png
 * 2) Add two routers to a new GNS3 project and start the devices.
 * 3) Set the router global, password, interface, line, and remote management configurations to various matching and mismatched configurations.
 * 4) Practice verifying and troubleshooting the configurations using the following commands.
 * 5) Troubleshoot and resolve VLAN and trunking problems.Cisco CCENT Router Switch 4 PCs.png
 * 6) Add a router, an EtherSwitch router and four VPCS PCs to a new GNS3 project and start the devices.
 * 7) Set the VLANs, port membership, encapsulation, trunking, and IP addressing to various matching and mismatched configurations.
 * 8) Practice verifying and troubleshooting the configurations using the following commands.
 * 9) Troubleshoot and resolve ACL issues.Cisco CCENT Routing 3.png
 * 10) Add three routers and two VPCS PCs to a new GNS3 project and start the devices.
 * 11) Configure IP addressing and static or dynamic routing to connect all devices.
 * 12) Test the configuration using the following commands from the routers and the PCs. Test all router and PC addresses. All tests should be successful.
 * 13) Configure standard and extended ACLs to various matching and mismatched configurations.
 * 14) Practice verifying and troubleshooting the configurations using the following commands.
 * 15) Troubleshoot and resolve Layer 1 problems.Cisco CCENT 2 Routers.png
 * 16) Add two routers to a new GNS3 project and start the devices.
 * 17) Set the link between the devices to various matching and mismatched configurations.
 * 18) Practice verifying and troubleshooting Layer 1 problems using the following commands.
 * 1) Practice verifying and troubleshooting the configurations using the following commands.
 * 2) Troubleshoot and resolve ACL issues.Cisco CCENT Routing 3.png
 * 3) Add three routers and two VPCS PCs to a new GNS3 project and start the devices.
 * 4) Configure IP addressing and static or dynamic routing to connect all devices.
 * 5) Test the configuration using the following commands from the routers and the PCs. Test all router and PC addresses. All tests should be successful.
 * 6) Configure standard and extended ACLs to various matching and mismatched configurations.
 * 7) Practice verifying and troubleshooting the configurations using the following commands.
 * 8) Troubleshoot and resolve Layer 1 problems.Cisco CCENT 2 Routers.png
 * 9) Add two routers to a new GNS3 project and start the devices.
 * 10) Set the link between the devices to various matching and mismatched configurations.
 * 11) Practice verifying and troubleshooting Layer 1 problems using the following commands.
 * 1) Practice verifying and troubleshooting the configurations using the following commands.
 * 2) Troubleshoot and resolve Layer 1 problems.Cisco CCENT 2 Routers.png
 * 3) Add two routers to a new GNS3 project and start the devices.
 * 4) Set the link between the devices to various matching and mismatched configurations.
 * 5) Practice verifying and troubleshooting Layer 1 problems using the following commands.
 * 1) Add two routers to a new GNS3 project and start the devices.
 * 2) Set the link between the devices to various matching and mismatched configurations.
 * 3) Practice verifying and troubleshooting Layer 1 problems using the following commands.

Lesson Summary

 * Troubleshooting is a logical, systematic search for the source of a problem so that it can be solved, and so the product or process can be made operational again.
 * Troubleshooting requires identification of the malfunction(s) or symptoms within a system. Then, experience is commonly used to generate possible causes of the symptoms. Determining the most likely cause is a process of elimination - eliminating potential causes of a problem. Finally, troubleshooting requires confirmation that the solution restores the product or process to its working state.
 * A basic principle in troubleshooting is to start from the simplest and most probable possible problems first.
 * Serial substitution involves checking each component in a system one by one, substituting known good components for each potentially suspect one.
 * Bisection involves separating a larger system into two or more subsystems to isolate and identify problems and causes.
 * One of the core principles of troubleshooting is that reproducible problems can be reliably isolated and resolved.
 * Intermittent problems are often the result of components that are thermally sensitive, because the resistance of a circuit varies with the temperature of the conductors in it.
 * Troubleshooters must always consider the possibility that there is more than one fault causing a given system failure.
 * Troubleshoot common problems associated with IP addressing and host configurations using the,  ,  ,  ,  ,  ,  ,  ,  ,  , and   commands.
 * Troubleshoot VLAN and trunking problems using the,  , and   commands.
 * Troubleshoot ACL issues using the,  , and   commands.
 * Troubleshoot Layer 1 problems using the  and   commands.

Key Terms

 * CRC (cyclic redundancy check)
 * An error-detecting code commonly used in digital networks and storage devices to detect accidental changes to raw data.


 * duplex mismatch
 * A condition where two connected devices operate in different duplex modes, that is, one operates in half duplex while the other one operates in full duplex.


 * error disabled (err-disabled)
 * A error situation detected on a port, resulting in the software shutting down that port.


 * giant
 * An Ethernet frame that is longer than the IEEE standard 1,518 bytes.


 * late collision
 * A collision that occurs more than 64 octets into the frame.


 * runt
 * An Ethernet frame that is less than the IEEE 802.3's minimum length of 64 octets.


 * up and up
 * Refers to the two interface states of line status and protocol status both being enabled.

Assessments

 * Flashcards: Quizlet: CCENT - Troubleshooting
 * Quiz: Quizlet: CCENT - Troubleshooting