CISCO - ITN module 9
The ARP request is encapsulated in an Ethernet frame using the following header information:
- Destination MAC address - Source MAC address - Type
ARP provides two basic functions:
- Resolving IPv4 addresses to MAC addresses - Maintaining a table of IPv4 to MAC address mappings
The sending device will search its ARP table for a destination IPv4 address and a corresponding MAC address only IF...
- the packet's destination IPv4 address is on the same network as the source IPv4 address, the device will search the ARP table for the destination IPv4 address. or - the destination IPv4 address is on a different network than the source IPv4 address, the device will search the ARP table for the IPv4 address of the default gateway.
What two protocols are used to determine the MAC address of a known destination device IP address (IPv4 and IPv6)?
ARP and ND
Which statement is true about ARP?
ARP entries are cached temporarily
What is an attack using ARP?
ARP poisoning
Only the device with the target IPv4 address associated with the ARP request will respond with an ARP reply. The ARP reply is encapsulated in an Ethernet frame using the following header information:
Destination MAC address Source MAC address Type
The Layer 2 Ethernet frame contains the following:
Destination MAC address and Source MAC address
When a device sends an Ethernet Layer 2 frame, it contains these two addresses:
Destination MAC address and Source MAC address
Removing Entries from an ARP Table
For each device, an ARP cache timer removes ARP entries that have not been used for a specified period of time. The times differ depending on the operating system of the device.
the Neighbor Discovery protocol
If your network is using the IPv6 communications protocol, ______ is what you need to match IPv6 addresses to MAC addresses
What two functions are provided by ARP?
Maintains a table of IPv4 to MAC address mappings Resolves IPv4 addresses to MAC addresses
ND provides address resolution, router discovery, and redirection services for IPv6 using ICMPv6. ICMPv6 ND uses five ICMPv6 messages to perform these services:
Neighbor Solicitation messages Neighbor Advertisement messages Router Solicitation messages Router Advertisement messages Redirect Message
Which two ICMPv6 messages are used in to determine the MAC address of a known IPv6 address?
Neighborhood advertisement, and neighborhood solicitation
There are two primary addresses assigned to a device on an Ethernet LAN:
Physical address (the MAC address) and Logical address (the IP address)
Where is the ARP table stored on a device?
RAM
Which two ICMPv6 messages are used in SLAAC?
Router Advertisement Router Solicitation
The Layer 3 IP packet contains the following:
Source IPv4 address and Destination IPv4 address
What destination MAC address would be included in a frame sent from a source device to a destination device on the same local network?
The MAC address of the destination device
What destination MAC address would be included in a frame sent from a source device to a destination device on a remote local network?
The MAC address of the local router interface
Source MAC address
This is MAC address of the sender of the ARP request.
Destination MAC address
This is a broadcast address FF-FF-FF-FF-FF-FF requiring all Ethernet NICs on the LAN to accept and process the ARP request.
Physical address (the MAC address)
Used for NIC to NIC communications on the same Ethernet network.
Logical address (the IP address)
Used to send the packet from the source device to the destination device. The destination IP address may be on the same IP network as the source or it may be on a remote network.
ICMPv6 Neighbor Solicitation messages
are sent using special Ethernet and IPv6 multicast addresses. This allows the Ethernet NIC of the receiving device to determine whether the Neighbor Solicitation message is for itself without having to send it to the operating system for processing.
ICMPv6 Neighbor Solicitation and Neighbor Advertisement messages
are used for MAC address resolution.
Layer 2 physical addresses (i.e., Ethernet MAC addresses) are used to
deliver the data link frame with the encapsulated IP packet from one NIC to another NIC that is on the same network. If the destination IP address is on the same network, the destination MAC address will be that of the destination device.
Neighbor Solicitation and Neighbor Advertisement messages are used for
device-to-device messaging such as address resolution (similar to ARP for IPv4). Devices include both host computers and routers.
Router Solicitation and Router Advertisement messages are for
messaging between devices and routers. Typically router discovery is used for dynamic address allocation and stateless address autoconfiguration (SLAAC).
To what type of address are ICMPv6 neighbor solicitation messages sent?
multicast
Which command could be used on a Cisco router to view its ARP table?
show ip arp
A device uses Address Resolution Protocol (ARP) to determine
the destination MAC address of a local device when it knows its IPv4 address.
When the destination IP address (IPv4 or IPv6) is on a remote network...
the destination MAC address will be the address of the host default gateway (i.e., the router interface).
ARP spoofing
uses false ARP replies to map any IP address to any MAC address
Address Resolution Protocol, or ARP
what you need to map IPv4 addresses to MAC addresses
As a broadcast frame, an ARP request
is received and processed by every device on the local network.
