ITNv7 Lesson 9 - Address Resolution

physical address

Used for NIC to NIC communication on the same Ethernet network.

MAC address

logical address

The address for each node on an IP network used to deliver packets to the source to the destination device.. The IP address.

ARP table/ ARP cache

A database of records that maps MAC addresses to IP addresses. Stored in RAM and used by the ARP utility to supply the MAC addresses of network nodes, given their IP addresses. .

ARP requests

Received and processed by every device on the local network.

Same network

The device searches the ARP table for the destination IPv4 address.

Different network

The device searches the ARP table for the IPv4 address of the default gateway.

Neighbor Discovery

Provide address resolution, router discovery, and redirection services for IPv6 using ICMPv6

Neighbor Solicitation (NS)

A message defined by the IPv6 Neighbor Discovery Protocol (NDP), used to ask a neighbor to reply with a Neighbor Advertisement, which lists the neighbor's MAC address.

Neighbor Advertisement (NA)

A message defined by the IPv6 Neighbor Discovery Protocol (NDP), used to declare to other neighbors a host's MAC address. Sometimes sent in response to a previously received NDP Neighbor Solicitation (NS) message.

Router Solicitation (RS)

A message defined by the IPv6 Neighbor Discovery Protocol (NDP), used to ask any routers on the link to reply, identifying the router, plus other configuration settings (prefixes and prefix lengths).

Router Advertisement (RA)

A message defined by the IPv6 Neighbor Discovery Protocol (NDP), used by routers to announce their willingness to act as an IPv6 router on a link. These can be sent in response to a previously received NDP Router Solicitation (RS) message.

Redirect Message

Used for better next-hop selection

What is the purpose of ARP?

ARP is the protocol used to discover the MAC address of any host an the local network.

When a PC wants to send data on the network, it knows the IP address of the destination, but it also needs to know the MAC address of the destination.

When will a switch flood a frame out every post but the source port?

When the destination address is a broadcast address.

When the destination address is unknown

The destination MAC address used in an ARP request frame

FFFF.FFFF.FFFF

arp -d command

Clears the ARP cache content.

Useful when a network technician wants to ensure the cache is populated with updated information.

IPV6 Neighbor Discovery

Used in place of ARP for IPv6 address resolution by sending neighbor solicitation and neighbor advertisement messages.

ARP spoofing

a malicious host intercepts ARP requests and replies to them so that network hosts will associate IP addresses to the wrong MAC address (a malicious host address)

neighbor solicitation and neighbor advertisement

Used by ICMPv6 neighbor discovery for IPv6 address resolution.

destination MAC address

Examined in the Ethernet frame header by a Layer 2 device to determine which path (interface or port) should be used to send the data onward to the destination device