CCNA Cisco Certified Network Associate Study Guide - FTP Server

TCP/IP and the DoD Model 123
If you remember reading about the Data Link layer and the different
frame types in Chapter 1, you should be able to look at the above trace and
tell me what type of Ethernet frame this is. The only fields are destination
hardware address, source hardware address, and Ether-type field. The only
frame that uses an Ether-type field is an Ethernet_II frame. (SNAP uses an
Ether-type field also, but only within an 802.2 LLC field, which is not
present in the frame.)
Address Resolution Protocol (ARP)
The Address Resolution Protocol (ARP) finds the hardware address of a host
from a known IP address. Here’s how it works: When IP has a datagram to
send, it must inform a Network Access protocol, such as Ethernet or Token
Ring, of the destination’s hardware address on the local network. (It has
already been informed by upper-layer protocols of the destination’s IP
address.) If IP doesn’t find the destination host’s hardware address in the
ARP cache, it uses ARP to find this information.
As IP’s detective, ARP interrogates the local network by sending out a
broadcast asking the machine with the specified IP address to reply with its
hardware address. In other words, ARP translates the software (IP) address
into a hardware address—for example, the destination machine’s Ethernet
board address—and from it, deduces its whereabouts. This hardware address
is technically referred to as the media access control (MAC) address or physical
address. Figure 3.8 shows how an ARP might look to a local network.
FIGURE 3.8 Local ARP broadcast
I need the Ethernet
address of 10.1.1.2
10.1.1.1 10.1.1.2
IP: 10.1.1.2 = ???
IP: 10.1.1.2
Ethernet: 4523.7985.7734
I heard that broadcast.
The message is for me.
Here is my Ethernet address.