CNT 140 chapter 13
What does ICMP stand for ?
Internet Control Message Protocol
An Time Exceeded message sent by a router is used to indicated what for both IPv4 and IPv6?
That a packets TTL or HOP limit field has decremented to 0 and that the packet has been dropped.
Which tool uses the Time Exceeded messages ?
traceroute
A network administrator is testing network connectivity by issuing the ping command on a router. Which symbol will be displayed to indicate that a time expired during the wait for an ICMP echo reply message? $ U ! .
.
Some of the Destination Unreachable codes for ICMPv4 are as follows:
0-Net unreachable 1-Host unreachable 2-Protocol unreachable 3-Port unreachable
Some of the Destination Unreachable codes for ICMPv6 are as follows:
0-No route to destination 1-Communcation with the destination is administratively prohibited (firewall) 2-Beyound scope of the source address 3-Address unreachable 4-Port unreachable
After all the requests are sent, the ping utility provides a summary of what ?
A summary that includes the success rate and average round trip time to the destination .
What can an ICMP ECHO message be used for ?
To test the reachability of a host on an IP network.
What is ping used for ?
Ping is an IPv6 and IPv4 testing utility that uses ICMP echo request and echo reply messages to test connectivity between hosts.
Type of connectivity tests performed with ping include the following:
Pinging the local loopback Pinging the default gateway Pinging the remote host
What is the purpose of the ICMP protocol ?
The purpose of these messages from the ICMP protocol is to provide feedback about issues related to the processing of IP packets under certain conditions, not to make IP reliable .
How is round trip time calculated ?
The round trip time is the time a packet takes to reach the remote host and for the response from the host to return.
what field content is used by ICMPv6 to determine that a packet has expired ? Hop Limit Field CRC Field TTL Field Time Exceed Field
Hop Limit Field
The types of ICMP messages, and the reasons why they are sent, are extensive. The ICMP messages common to both ICMPv4 and ICMPv6 and discussed in this module include:
Host reachability Destination or Service Unreachable Time Exceeded
What is traceroute /tracert command used for ?
Traceroute (tracert) is a utility that generates a list of hops that were successfully reached along the path. This list can provide important verification and troubleshooting information. If the data reaches the destination, then the trace lists the interface of every router in the path between the hosts. If the data fails at some hop along the way, the address of the last router that responded to the trace can provide an indication of where the problem or security restrictions are found.
True or False. ICMPv6 ND also includes the redirect message, which has a similar function to the redirect message used in ICMPv4
True
Which utility uses the Internet Control Messaging Protocol (ICMP) ? DNS ping NTP RIP
ping
Which two things can be determined by using the ping command ? The average time it takes a packet to reach the destination and for the response to return to the source the IP address of the router nearest the destination device the average time it takes each router in the path between source and destination to respond the number of routers between the source and destination device the destination device is reachable through the network
the average time it takes a packet to reach the destination and for the response to return to the source the destination device is reachable through the network
How does traceroute us the IPv6 hop limit and IPv4 TTL fields ?
The first sequence of messages sent from traceroute will have a TTL field value of 1. This causes the TTL to time out the IPv4 packet at the first router. This router then responds with an ICMPv4 Time Exceeded message. Traceroute now has the address of the first hop. Traceroute then progressively increments the TTL field (2, 3, 4...) for each sequence of messages. This provides the trace with the address of each hop as the packets time out further down the path. The TTL field continues to be increased until the destination is reached, or it is incremented to a predefined maximum. After the final destination is reached, the host responds with either an ICMP Port Unreachable message or an ICMP Echo Reply message instead of the ICMP Time Exceeded message.
What information can the list generated by the traceroute command provide ?
The list can provide important verification and troubleshooting information.
Which command can be used to test connectivity between two devices using echo request and echo reply messages ? ipconfig ICMP pin nestat
ping
A user who is unable to connect to the file server contacts the help desk. The helpdesk technician asks the user to ping the IP address of the default gateway that is configured on the workstation. What is the purpose for this ping command? to test that the host has the capability to reach other networks to obtain a dynamic IP address from the server to resolve the domain name of the file server to its IP address to request that gateway forward the connection request to the file server
to test that the host has the capability to reach other networks
A technician is troubleshooting a network where it is suspected that a defective node in the network path is causing packets to be dropped. The technician only has the IP address of the end point device and does not have any details of the intermediate devices. What command can the technician use to identify the faulty node? ping ipconfig /flushdns ipconfig /displaydns tracert
tracert
An asterisk in a in a round trip indicates what ?
Indicates a lost or unreplaced packet.
What does a ping time out message indicate ?
It indicates that a response was not received. This may indicate that there is a problem, but could also indicate that security features blocking ping messages have been enabled on the network.
What two new IPv6 ICMPv6 protocols deal with duplicate address detection and address resolution ?
Neighbor Solicitation (NS) message Neighbor Advertisement (NA) message
What can the ping command be used to measure ?
Network Performance
What two new IPv6 ICMPv6 protocols deal with Dynamic address allocation ?
Router Solicitation (RS) message Router Advertisement (RA) message
ICMPv6 includes four new protocols as part of the Neighbor Discovery Protocol (ND or NDP).What are they ?
Router Solicitation (RS) message Router Advertisement (RA) message Neighbor Solicitation (NS) message Neighbor Advertisement (NA) message
Which type of ICMPv6 message would a host sent to acquire an IPv6 configuration when booting up ? Neighbor Advertisement (NA) message Neighbor Solicitation (NS) message Router Advertisement (RA) message Router Solicitation(RS) message
Router Solicitation(RS) message
Which layer 3 protocol is used to provide error messages and information messages when communicating with another IP device ?
ICMP
Which protocol is used by IPv4 and IPv6 to provide error messaging ? ARP DHCP NDP ICMP
ICMP
Which protocol provides feedback from the destination host to the source host about errors in packer deliver ? DNS BOOTP ICMP ARP
ICMP
What is a function of the tracert command that differs from the ping command when they are used on a workstation ? The tracert command shows the information of routers in the path The tracert command reaches the destination faster The tracet command sends one ICMP message to each hop in the path The tracert command is used to teat the connectivity between two devices ?
The tracert command shows the information of routers in the path
What kind of information can the round trip from a traceroute provide ?
This information can be used to locate a problematic router in the path or may indicate that the router is configured not to reply. If the display show high response times or data losses from a particular hop, this is an indication that the resources of the router or its connections may be stressed.
Which two types of ICMP messages are common to both ICMPv4 and ICMPv6 ? Destination or Service Unreachable Hostname resolution Source Unreachable Time Exceeded
Time Exceeded Destination or Service Unreachable
What two types of messages does the ping command send to test reachability of a host on an IP network ?
Echo request and Echo reply
A user calls to report that a PC cannot access the internet. The network technician asks the user to issue the command ping 127.0.0.1 in a command prompt window. The user reports that the result is four positive replies. What conclusion can be drawn based on this connectivity test? The IP address obtained from the DHCP server is correct The PC can access the network. The problem exists beyond the local network The PC can access the Internet. However, the web browser may not work. The TCP/IP implementation is functional
The TCP/IP implementation is functional
What message is sent by a host to check the uniqueness of an IPv6 address before using that address ? echo request neighbor solicitation route solicitation ARP request
neighbor solicitation
Which ICMP message is used by the traceroute utility during the process of finding the path between two end hosts ? ping time exceeded redirect destination unreachable
time exceeded
When a host or gateway receives a packet that it cannot deliver, it uses what type of message to notify the source device ?
ICMP Destination Unreachable message to notify the source that the destination or service is unreachable.
A network administrator can successfully ping the server at www.cisco.com, but cannot ping the company web server located at an ISP in another city. Which tool or command would help identify the specific router where the packet was lost or delayed? netstat traceroute ipconfig telnet
traceroute
