6.5 Network Communication Troubleshooting Flashcards
Describe Ping host Troubleshooting Ping host C Task
Often the best way to start troubleshooting a problem is to ping the host you are trying to contact. This verifies the reported problem. If the ping is successful, the problem is not related to network connectivity. Check other problems, such as name resolution or service access.
Describe Ping host Troubleshooting Ping host D Task
If you cannot contact a specific remote host, try pinging another host in the same remote network. If the ping is successful, then the problem is with the remote host, such as a misconfiguration, broken link, or it is unavailable.
Describe Ping host Troubleshooting Ping host E Task
If you cannot contact any host in the remote network, try pinging hosts on other remote networks. You might try several other networks. If the pings are successful, or if you can contact some remote networks and not others, then the problem is with the routing path between your network and the specific remote network. Use the tracert (traceroute on Linux) command to check the path to the problem network.
Describe Ping host Troubleshooting Ping the default gateway Task
If you cannot contact any remote network, ping the default gateway router. If the ping is successful, but you still cannot contact any remote host, have the router administrator verify the router configuration. Check for broken links to the remote network; interfaces that have been shut down; and access control lists or other controls that might be blocking traffic.
Describe Ping host B Task
If you cannot contact the default gateway router, ping other hosts on the local network. If the pings are successful, check the default gateway router.
Describe Troubleshoot the local host connection or configuration
If you cannot communicate with any host on the local network, then the problem is likely with the local host or its connection to the network. Troubleshoot by doing the following:
Check physical connectivity
Validate the TCP/IP configuration on the local host
Validate IP configuration settings
What is (ICMP)
Internet Control Message Protocol - a special-purpose message mechanism added to the TCP/IP suite that lets computers and routers in an internetwork report errors or provide information about unexpected circumstances.
What protocol do hosts use to send error messages to other hosts
ICMP
Describe echo message from the ICMP protocol
The ICMP echo message is used to discover hosts and networks and to verify that they are reachable. The ping utility is a popular utility that uses ICMP echo messages.
Describe the Destination unreachable message from the ICMP protocol
The destination unreachable message is sent if a packet cannot reach its destination. This can happen for a variety of reasons. It might indicate the host is unavailable or that there were problems detected in the packet header.
Describe the Time exceeded message from the ICMP protocol
The time exceeded message is sent when the packet’s time-to-live (TTL) counter has expired.
Describe the Redirect message from the ICMP protocol
The redirect message is sent from a router to the sending device to indicate that a different route should be chosen for the packet. The redirect message can be sent if a better route is in the router’s table or if the selected route is unavailable or congested.
Describe the Source quench from the ICMP protocol
The source quench message is sent by a receiving device to indicate that the flow of packets is too fast. When a sending device receives a source quench message, it slows its rate of transmission.
Describe the Router discovery from the ICMP protocol
The router discovery message is a special broadcast message sent by hosts to discover the routers on a network. Routers respond to the message, announcing their presence. They do not exchange routing information, but simply broadcast their availability.
What layer of the OSI model does Telnet work on
Application layer
