Module 13 ICMP
What is the standard TTL number of hops used by Windows to avoid Loops?
128 hops
What is included in a Router Advertisement (RA) message that an IPv6 enabled router will send every 200 seconds?
Addressing information for hosts: prefix, prefix length, DNS address, domain name.: Prefix: 1st four hextets of IPv6 address Prefix Length: /64 Link-Local Address as the default gateway
Which utility uses the Internet Control Messaging Protocol (ICMP)? DNS NTP Ping RIP
Ping Topic 13.1.0 - ICMP is used by network devices to send error messages.
Which command can be used to test connectivity between two devices using echo request and echo reply messages? ipconfig netstat ICMP ping
Ping Topic 13.2.0 - Ping is used to test connectivity between end devices. It can be used with both IPv4 and IPv6. Ping uses the ICMP protocol which issues an echo request/echo reply. The ipconfig command is used at the command line of a Windows computer to display IP addressing information. Netstat is used to display the local routing table.
A user issues a ping 2001:db8:FACE:39::10 command and receives a response that includes a code of 3. What does this code represent? address unreachable network unreachable host unreachable protocol unreachable
address unreachable
A user issues a ping fe80:65ab:dcc1::100 command and receives a response that includes a code of 3. What does this code represent? address unreachable communication with the destination administratively prohibited beyond scope of the source address no route to destination
address unreachable
Which two types of ICMP messages are common to both ICMPv4 and ICMPv6? Destination Service unreachable Hostname Resolution IP configuration Source Unreachable Time Exceeded
Destination Service Unreachable Time Exceeded
What TTL number is used by routers for hops to avoid Loops?
64 hops
After running a traceroute on an IP address, the output shows the first hop which will be the ________________________
default gateway router's exit interface
Which protocol is used by IPv4 and IPv6 to provide error messaging? ICMP NDP DHCP ARP
ICMP Topic 13.1.0 - ICMP is used by IPv4 and IPv6 to provide for messages to be sent in the event of certain errors and for informational purposes.
What field content is used by ICMPv6 to determine that a packet has expired? TTL Hop Limit CRC Time Exceeded
Hop Limit Topic 13.1.0 - ICMPv6 sends a Time Exceeded message if the router cannot forward an IPv6 packet because the packet expired. The router uses a hop limit field to determine if the packet has expired, and does not have a TTL field.
What 3 types of ICMP Messages are used in both ICMPv4 and ICMPv6?
Host reachability (Echo Request; Echo Reply) Destination or Service Unreachable Time Exceeded
When this ICMPv6 protocol is set up, every 200 seconds a router sends out a message to all devices on the local network. What type of message is this? Router Advertisement (RA) Router Solicitation (RS) Neighbor Solicitation (NS) Neighbor Advertisement (NA)
Router Advertisement Message (RA) to provide addressing info IPv6 enabled hosts.
What is a consequence of configuring a router with the ipv6 unicast-routing global configuration command?
The IPv6 enabled router interfaces begin sending ICMPv6 Router Advertisement messages.
What is the standard TTL number of hops used by Linux/MAC to avoid Loops?
64 hops called Optimal TTL
ICMPv6 Host Reachability uses 2 message types:
Echo Request Echo Reply
What will happen if the default gateway address is incorrectly configured on a host?
The host cannot communicate with hosts in other networks.
Network administrators can limit or prohibit the entry of ICMP messages which prohibits ping requests due to security reasons. By what method is this done?
Using Access Control Lists (ACLs) on router interfaces
Which ICMPv6 message is sent when the IPv6 hop limit field of a packet is decremented to zero and the packet cannot be forwarded? network unreachable time exceeded protocol unreachable port unreachable
time exceeded
IPv6 enabled devices that connect to a new network are assigned a global IPv6 unicast or link-local unicast address. The device may then perform _________ what type of check to ensure the IPv6 address is unique? To check the uniqueness of a message, the device sends ________ Message
The device performs a DAD (Duplicate Address Detection) and does this by sending a Neighbor Solicitation (NS)message with its own IPv6 adddress.
A user executes a traceroute over IPv6. At what point would a router in the path to the destination device drop the packet? when the value of the Hop Limit field reaches 255 when the value of the Hop Limit field reaches zero when the router receives an ICMP time exceeded message when the target host responds with an ICMP echo reply message
when the value of the Hop Limit field reaches zero
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
! Topic 13.2.0 - When the ping command is issued on a router, the most common indicators are as follows: ! - indicates receipt of an ICMP echo reply message . - indicates a time expired while waiting for an ICMP echo reply message U - an ICMP message of unreachability was received
What steps should be taken to troubleshoot a PC's connectivity problems using Ping Utility?
1. When have PC that has connectivity issues, first ping the default gateway router's IP address. If you cant get to the default gateway, might have the wrong LLA. 2. See if PC can successfully ping to another host on the network. If so, the problem may be with the router. 3. If you can ping the default gateway successfully, then try to ping a host outside of the local network. DNS may be the problems if can't reach a website.
A technician uses the ping 127.0.0.1 command. What is the technician testing? the TCP/IP stack on a network host connectivity between two adjacent Cisco devices connectivity between a PC and the default gateway connectivity between two PCs on the same network physical connectivity of a particular PC and the network
the TCP/IP stack on a network host
Why might you ping a remote host?
to check the ability of a local host to communicate across an internetwork. Successful ping confirms communication on the local network
Which protocol is used by the traceroute command to send and receive echo-requests and echo-replies? SNMP ICMP Telnet TCP
ICMP Explanation: Traceroute uses the ICMP (Internet Control Message Protocol) to send and receive echo-request and echo-reply messages.
What is DAD (Duplicate Address Detection)?
In IPv6, Duplicate Address Detection (DAD) is used in place of ARP. An IPv6 host performs DAD by sending a neighbor solicitation (NS) message to its own IPv6 address to ensure the uniqueness of the address prior to using it.
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? ipconfig netstat telnet traceroute
traceroute Topic 13.2.0 - The traceroute command provides connectivity information about the path a packet takes to reach the destination and about every router (hop) along the way. It also indicates how long a packet takes to get from the source to each hop and back.
What is the purpose of ICMP messages? to inform routers about network topology changes to ensure the delivery of an IP packet to provide feedback of IP packet transmissions to monitor the process of a domain name to IP address resolution
Explanation: The purpose of ICMP messages is to provide feedback about issues that are related to the processing of IP packets. to provide feedback of IP packet transmissions Explanation: The purpose of ICMP messages is to provide feedback about issues that are related to the processing of IP packets.
Which protocol provides feedback from the destination host to the source host about errors in packet delivery? ICMP DNS ARP BOOTP
ICMP Topic 13.1.0 - The ICMP protocol operates at Layer 3 of the OSI model, which is the Internet layer of the TCP/IP model. ICMP encapsulates the ping and traceroute commands.
What message is sent by a host to check the uniqueness of an IPv6 address before using that address? router solicitation (RS) Echo Request ARP Request Neighbor Solicitation (NS)
Neighbor Solicitation Topic 13.1.0 - In IPv6, Duplicate Address Detection (DAD) is used in place of ARP. An IPv6 host performs DAD by sending a neighbor solicitation (NS) message to its own IPv6 address to ensure the uniqueness of the address prior to using it.
What information does traceroute utility provide when used to test the path between 2 hosts?
Provides a list of hops that were successfully reached along the path Provides round-trip time for each hop along the path and indicates if a hop fails to respond. AN asterisk (*) is used to indicate a lost or unreplied packet.
Which type of ICMPv6 message would a host send to acquire an IPv6 configuration when booting up? Neighbor Advertisement (NA) Message Neighbor Advertisement (NS) Message Router Advertisement (RA) Message Router Solicitation (RS) Message
RS message ( An IPv6 enabled host booting up would send an ICMPv6 router solicitation message. In IPv6 enabled router would respond with a Router Advertisement (RA) message)
When a new IPv6 device comes up on a network, it will look for the closest default gateway router and will use what type of message to do so? Router Advertisement (RA) Router Solicitation (RS) Neighbor Solicitation (NS) Neighbor Advertisement (NA)
Router Solicitation (RS)
What are the 4 new protocols used in ICMPv6 that don't exist in ICMP4?
Router Solicitation (RS) Message Router Advertisement Message (RA) Message Neighbor Solicitation (NS) Message Neighbor Advertisement (NA) Message
In IPv6 a global unicast address or Link-local address can be used for the default gateway router. By default what method does SLAAC use?
SLAAC uses auto-assigned Link-Local address
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 PC can access the Internet. However web browser may not work. The TCP/IP implementation is functional PC can access the network. Problem exists beyond the local network IP address obtained from DHCP server is correct.
The TCP/IP Implementation is functional. Topic 13.2.0 - The ping 127.0.0.1 command is used to verify that the TCP/IP stack is functional. It verifies the proper operation of the protocol stack from the network layer to physical layer, without sending a signal on the media. That is, this test does not go beyond the PC itself. For example, it does not detect whether a cable is connected to the PC or not.
Which ICMP message is used by the traceroute utility during the process of finding the path between two end hosts? Ping Time Exceeded Destination Unreachable Redirect
Time Exceeded Topic 13.1.0 - Traceroute progressively increments the TTL (IPv4) or hop limit (IPv6) field (1, 2, 3, 4...) for sending sequence of ping commands. When a router senses that the TTL or hop limit is 0, it will discard the packet and send a time exceeded message to the source of the traceroute. The returned message contains the IP address of the router that discarded the packet. Hence the traceroute utility learns the address of the router. This process continues and provides the trace with the address of each hop (router) as the packets continue traveling through routers to reach the destination.
A user issues a ping fe80:65ab:dcc1::100 command and receives a response that includes a code of 4. What does this code represent? port unreachable host unreachable protocol unreachable network unreachable
port unreachable
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/displaydns ipconfig/flushdns tracert
Tracert Topic 13.2.0 - The ping command is used to verify connectivity to a device, the commands ipconfig /flushdns will cause the adapter to flush the DNS cache, while ipconfig /**displaydns** will result in the display of the DNS information in the cache.
What is a function of the tracert command that differs from the ping command when they are used on a workstation? Tracert shows the info of routers in the path Tracert sends one ICMP message to each hop in the path Tracert reaches the destination faster Tracert is used to test the connectivity between two devices
Tracert shows the info of routers in the path Topic 13.2.0 - The tracert command sends three pings to each hop (router) in the path toward the destination and displays the domain name and IP address of hops from their responses. Because tracert uses the ping command, the travel time is the same as a standalone ping command. The primary function of a standalone ping command is to test the connectivity between two hosts.
True or False: in IPv6, a host using Stateless Address Autoconfiguration (SLAAC) will set its default gateway to the link-local address LLA of the router that sends a RA
True
A user issues a ping 2001:db8:FACE:39::10 command and receives a response that includes a code of 2 . What does this code represent? beyond scope of the source address communication with the destination administratively prohibited address unreachable no route to destination
beyond scope of the source address
A user issues a ping 2001:db8:FACE:39::10 command and receives a response that includes a code of 2. What does this code represent? beyond scope of the source address host unreachable protocol unreachable network unreachable
beyond scope of the source address
Which two things can be determined by using the ping command? (Choose two.) destination device is reachable through the network average time it takes each router in path between source and destination to respond average time it takes a packet to reach the destination and for response to return to the source the IP address of the router nearest the destination device The number of routers between the source and destination device
destination device is reachable through the network average time it takes a packet to reach the destination and for response to return to the source Topic 13.2.0 - A ping command provides feedback on the time between when an echo request was sent to a remote host and when the echo reply was received. This can be a measure of network performance. A successful ping also indicates that the destination host was reachable through the network.
A user issues a ping 192.135.250.103 command and receives a response that includes a code of 1. What does this code represent? host unreachable beyond scope of the source address address unreachable communication with the destination administratively prohibited
host unreachable
A user issues a ping 192.135.250.103 command and receives a response that includes a code of 1. What does this code represent? host unreachable protocol unreachable port unreachable network unreachable
host unreachable
A user issues a ping 10.10.14.67 command and receives a response that includes a code of 0. What does this code represent? network unreachable protocol unreachable port unreachable host unreachable
network unreachable
A user issues a ping 198.133.219.8 command and receives a response that includes a code of 0 . What does this code represent? network unreachable protocol unreachable port unreachable host unreachable
network unreachable
A user issues a ping 2001:db8:3040:114::88 command and receives a response that includes a code of 4. What does this code represent? port unreachable host unreachable protocol unreachable network unreachable
port unreachable
What source IP address does a router use by default when the traceroute command is issued? the highest configured IP address on the router a loopback IP address the IP address of the outbound interface the lowest configured IP address on the router
the IP address of the outbound interface Explanation: When sending an echo request message, a router will use the IP address of the exit interface as the source IP address. This default behavior can be changed by using an extended ping and specifying a specific source IP address.
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 resolve the domain name of the file server to its IP address to obtain dynamic IP address from server to request that the gateway forward the connection request to the file server. to test that the host has the capability to reach hosts on other network.
to test that the host has the capability to reach hosts on other network. /Topic 13.2.0 - The ping command is used to test connectivity between hosts. The other options describe tasks not performed by ping. Pinging the default gateway will test whether the host has the capability to reach hosts on its own network and on other networks.
