ARP, Gratuitous ARP and RARP Flashcards
What is ARP?
Address Resolution Protocol is used to resolve IP addresses into MAC Addresses
What is RFC 826?
A defining of Address Resolution Protocol.
What is needed by computers in order for network communication to happen?
MAC Address and IP Address of the destination
What is ARP used for?
To find out a MAC address when the IP address of the destination is known.
What kind of cast is sent out for an ARP request?
Broadcast.
What is included in an ARP Request or ARP Reply?
Source & Target Hardware Address (MAC Address) and Source & Target Protocol Address (IP Address)
Where are ARP Requests located?
An ethernet frame.
What’s an ARP Cache?
A (temporary) table of all known IP Address to MAC address mapping
Whats the command for IP Address to MAC address mapping?
Win/Mac/Linux Command: “arp -a”, Cisco IOS (router or switch): “show arp”
What do computers do before send network communication?
Reference their ARP Cache
If no MAC Address is present then for the destination of the communication on a computer, what happens?
An ARP Request is sent out.
What is Gratuitous ARP?
An ARP announcement to update other hosts ARP tables without the need for an ARP Request
What are the benefits of Gratuitous ARP?
Helps to update the network faster when there was a recent change to a hosts IP Address.
What are the disadvantages of Gratuitous ARP?
Sometimes there are security risks associated.
What is RARP?
Reverse Address Resolution Protocol was used to resolve MAC Addresses into IP Addresses?
What replaces RARP?
BOOTP and then DHCP.
What are the disadvantages of RARP?
Required servers on EVERY network.
What is DHCP used for?
Dynamic Host Configuration Protocol is used to assign IP Addresses to hosts on a network.
Is RARP Valid?
No.
What’s an example of Gratuitous ARP being used?
When a hosts IP Address has been updated, it will send an ARP announcement to update other hosts ARP Tables.
