IGRP Load Balancing and Network Troubleshooting

Questions and Answers

Which command can be used to test Layer 3 connectivity?

ping

What type of errors can be identified at Layer 1?

Broken cables

Which troubleshooting tool is best suited for identifying the path a packet takes from source to destination?

traceroute

Which command would be used to monitor router activity in real-time?

debug Signup and view all the answers

In the context of software verification, which tool indicates proper functioning of upper-layer applications and lower layer services?

telnet Signup and view all the answers

What command can be used to gather detailed information about the routes installed on a router?

show ip route Signup and view all the answers

Which command is appropriate to confirm Layer 1 and Layer 2 problems?

show interfaces Signup and view all the answers

To identify the path packets take between networks, which command is most suitable?

traceroute Signup and view all the answers

Which command is used to monitor router activity?

debug Signup and view all the answers

For verifying the application layer software between source and destination stations, which command should be used?

telnet Signup and view all the answers

What does it indicate if the interface is up and the protocol is down according to the provided text?

A Layer 2 problem exists Signup and view all the answers

What should be done first when a cabling problem is suspected according to the text?

Disable the interfaces with the no shutdown command Signup and view all the answers

What does the appearance of an asterisk (*) during a traceroute indicate?

The packet failed Signup and view all the answers

Which command is useful for debugging connectivity issues according to the text?

show cdp neighbors detail Signup and view all the answers

If Telnet failure is not related to connectivity, what could be a likely cause according to the text?

Access permission problems Signup and view all the answers

Study Notes

Network Troubleshooting

IGRP uses load balancing between two links after the variance command is executed

Troubleshooting by OSI Layers

Layer 1 errors can include:
- Broken, disconnected, or intermittent cables
- Cables connected to the wrong ports
- Rollover, crossover, or straight-through cables used incorrectly
- Transceiver problems
- DCE or DTE cable problems
- Devices turned off
Layer 2 errors can include:
- Improperly configured serial or Ethernet interfaces
- Improper encapsulation set
- Improper clockrate settings on serial interfaces
- Network interface card (NIC) problems
Layer 3 errors can include:
- Routing protocol not enabled or wrong routing protocol enabled
- Incorrect IP addresses or subnet masks

Layer 3 Troubleshooting using Ping

Used for troubleshooting Layer 3 issues

Layer 7 Troubleshooting using Telnet

A successful Telnet connection indicates that the upper-layer application and the services of lower layers are functioning properly
If Telnet connection fails, verify lower layer connectivity

Troubleshooting Router Issues

Use the show interfaces command to troubleshoot Layer 1 issues
The "line" parameter refers to the physical layer, while the "protocol" parameter refers to the Layer 2 protocol
If the interface is down, a hardware problem exists or it is administratively down
If the interface is up and the protocol is down, a Layer 2 problem exists

Troubleshooting using Show CDP

Use the show cdp neighbors detail command to troubleshoot connectivity issues
CDP can be a potential security hole, so it should be configured only on links between Cisco devices and disabled on user ports or links that are not locally managed

Troubleshooting using Traceroute

An asterisk (*) appears if the packet fails
The round trip time (RTT) is the time required to send an echo packet and get a response
The default maximum TTL for traceroute is 30

Router Commands

show ip route: To gather detailed information about the routes installed on the router
ping: To perform basic network connectivity tests
telnet: To verify the application layer software between source and destination stations
show interfaces: To confirm Layer 1 and Layer 2 problems
show ip route and show ip protocol: To identify routing issues
show cdp: To verify Layer 2 connectivity
traceroute: To identify the path packets take between networks
show controllers serial: To ensure the proper cable is attached
debug: To monitor router activity