Network+ - Lesson 6: Supporting IPv4 and IPv6

arp -s IPAddress MACAddress

Adds an entry to the ARP

A workstation cannot connect to a server application on a remote network. What is the first test you could perform to establish whether the workstation's link is OK?

Ping another local system, such as the default gateway.

ipconfig /registerdns

Registers the host with a DNS server.

ipconfig /release

Releases the IP address obtained from a DHCP Server so that the interface(s) will no longer have an IP address.

arp -a

Shows the ARP cache contents.

What output would you expect when running the command ip neigh?

IP:MAC address mappings held in the ARP cache of a Linux host.

Neighbor Discovery (ND) protocol

IPv6 protocol used to identify link local nodes.

Which command line tool is now most commonly used on Linux distributions to configure network interfaces?

'ip' is the most commonly used Linux command line tool used to gather information about the IP configuration of the network adapter or to configure the network adapter.

An IPv6 address is divided into two parts: the first 64 bits are used as a network ID, while the second 64 bits designate a specific interface. Unlike in IPv4, the interface address (or host ID portion) is always the same 64-bit length.

Note *

'ip addr' is the common syntax for configuring an interface in Linux.

Note*

Link local addresses span a single subnet (they are not forwarded by routers). Nodes on the same link are referred to as neighbors. The link local range is fe80::/10. Link local addresses start with a leading fe80, with the next 54 bits set to 0, and the last 64 bits are the interface ID.

Note*

Most modern dual stack systems will try to initiate communications using IPv6 by default. Most services are addressed using names rather than IP addresses. This means that the preference for IPv6 over IPv4 or the availability of either addressing method depends on the Domain Name Server (DNS) records for the network.

Note*

IPv6 loopback address.

0:0:0:0:0:0:0:1, also expressed as ::1

Name three IPv6 tunneling protocols.

6to4 automatic tunneling (depricated) IPv6 Rapid Deployment (6RD) Microsoft Windows Teredo protocol Generic Routing Encapsulation (GRE)

IPv6 unspecified address.

:: (0:0:0:0:0:0:0:0)

Tunneling

Can be used to deliver IPv6 packets across an IPv4 network. Tunneling means that IPv6 packets are inserted into IPv4 packets and routed over the IPv4 network to their destination.

Users on a floor served by a single switch cannot get a network connection. What is the best first step?

Check that the switch is powered on and reset it. If that does not work, check for other causes such as a poorly seated plug-in module.

ipconfig /flushdns

Clears the DNS resolver cache.

Advertisement (RA) messages

Packet sent by an IPv6-capable router to notify hosts about prefixes and autoconfiguration methods available on the local link

How do you manually stop a 'ping' command?

Ctrl+C

arp -d *

Deletes all entries in the ARP cache; it can also be used with IPAddress to delete a single entry.

ipconfig /all

Displays complete TCP/IP configuration parameters for each interface, including whether the Dynamic Host Configuration Protocol (DHCP) is enabled for the interface and the interface's hardware (MAC) address.

ipconfig /displaydns

Displays the Domain Name System (DNS) resolver cache.

What is an EUI-64, and how might it be used by IPv6?

Extended unique identifier (EUI) is IEEE's preferred term for a MAC address. EUI-64 is a 64-bit hardware interface ID. A 48-bit MAC address can be converted to an EUI-64 by using a simple mechanism. The EUI-64 can be used as the IPv6 interface ID, though a randomly generated token is often preferred.

True or false? 6to4 is a dual stack method of transitioning from IPv4 to IPv6.

False. 6to4 is a method of tunneling IPv6 packets over an IPv4 network. Dual stack means that hosts and routers process both IPv4 and IPv6 traffic simultaneously.

True or False? The arp utility will always show another host's MAC address if that host is on the same subnet.

False. While that is the function of the Address Resolution Protocol, the arp utility is used to inspect the ARP table cache, which may or may not contain the other host's address. Note that a standard means to ensure the MAC address is cached is to ping the destination address first. This is the basis of a utility called arping.

ipconfig /renew

Forces a DHCP client to renew the lease it has for an IP address.

Dual stack

Host operating multiple protocols simultaneously on the same interface. Most hosts are capable of dual stack IPv4 and IPv6 operation for instance.

What is ICMP

Internet Control Message Protocol (ICMP) is an IP-level protocol for reporting errors and status information supporting the function of troubleshooting utilities such as *ping*.

What is ifconfig?

It is a Linux command line tool for configuring network interface. It is part of the legacy net-tools package and has been largely deprecated on most modern Linux distributions.

In IPv6, how can a host obtain a routable IPv6 address without requiring manual configuration?

Stateless address autoconfiguration (SLAAC) allows a host to autoconfigure an interface by listening for Router Advertisements to obtain a network prefix.

A technician is troubleshooting a network and has asked your advice. He is trying to ping 192.168.16.192. The network has been subnetted with the custom mask 255.255.255.224. Why might this return a "Destination host unreachable" message?

The IP address resolves to the subnet network address, not a host address. Windows does not normally allow pinging the network address. Other OSs treat it as an alternative broadcast address, but most systems are configured to disallow such directed broadcasts for security reasons.

What does the 'arp' command do?

Windows command line utility to display and modify contents of host's cache of IP to MAC address mappings, as resolved by address resolution protocol (ARP) replies.

You have pinged the router for the local subnet and confirmed that there is a valid link. The local host cannot access remote hosts, however. No other users are experiencing problems. What do you think is the cause?

The router is not configured as the default gateway for the local host. You can ping it, but the host is not using it for routing.

True of False. The 'ping' command can test the network connections of both IPv4 and IPv6 hosts.

True.

True or False? Receiving an echo reply message indicates that the link between two hosts is operational.

True.

A Windows client workstation cannot access a help desk application server by its name support.515support.com. The service can be accessed using its IP address. What two command line tools should you use to identify possible causes of this issue?

Use ipconfig to report the DNS servers that the client is trying to use and verify they are correct. Use ping to verify connectivity with the DNS servers.

Which of the following IPv6 addresses is a valid unicast host address? fe80::218:8bff:fea7:bd37 fe80::219:d2ff::7850 ff02::219:d2ff:fea7:7850 ::/128

fe80::218:8bff:fea7:bd37

What is the Linux command that shows entries in the local ARP cache.

ip neigh

What is the command tool used to gather information about the IP configuration of a Windows host?

ipconfig