CCNA Module 9: Address Resolution

Use of Physical Address (MAC address) (layer to)

Used for NIC to NIC communications on the same Ethernet network

Use of Logical Address (IP address) (layer 3)

Used to send the packet from a source device to a destination device. Can be on the same IP network or a remote one

Address Resolution Protocol (ARP)

A protocol used to map IPv4 addresses to MAC addresses within a local network, enabling devices to discover each other's physical addresses.

(like ND)

Neighbor Discovery (ND)

A protocol used in IPv6 networks to discover other devices on the same local link, including their link-layer addresses, and to determine their status.

(like ARP)

ARP Request

Sent when a device needs to determine the MAC address that is associated with an IPv4 address

How are ARP messages encapsulated

directly into the frame with the source/destination MAC address, and the type

Are ARP table entries permanent?

No

Command on a router to show the ARP table

show ip arp

arp -a (for windows)

ARP poisoning attack

A threat actor uses spoofing to reply to an ARP request for a different IPv4 address, so it receives the packet instead.

ARP Functions

Maintains and Resolves a table of IPv4 to MAC address mappings

Neighbor Discovery (ND) use

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

ICMPv6 messages for ND

Neighbor Solicitation and Advertisement messages

Router Solicitation and Advertisement messages

Redirect Message

ND Address Resolution

Uses Neighbor solicitation (there) and advertisement (back) to look for MAC address of the device

SLAAC (Stateless address auto configuration)

an IPv6 feature that lets network devices automatically create their own unique IP addresses without needing a centralized DHCP server

involves Router Solicitation and Advertisement

When the destination IP address is on the same network, what will the MAC address be?

The destination device’s MAC address

When the destination IP address is on a different network, what will the MAC address be?

The host default gateway’s MAC address

When the destination IP address is the next-hop destination, what will the MAC address be?

The destination device’s MAC address

Which router component holds the routing table and ARP cache?

RAM

What destination address is used in an ARP request frame?

FFFF.FFFF.FFFF because an ARP request is an ethernet broadcast