A - Overview Of Network Addressing And Communication; Layer 2 Versus Layer 3; Address - Unicast Versus Broadcast Versus Multicast; Example Scenarios Of Network Addressing And Communication - HP Rx2620-2 - Integrity - 0 MB RAM Manual

A – Overview of Network Addressing and Communication
Understanding the concepts of network addressing is the key to understanding how HP's Network
Adapter Teaming works. This section provides a brief overview of network addressing as a
baseline for explaining how HP's Network Adapter Teaming can create one logical network port
from a team of two or more ports.

Layer 2 Versus Layer 3

Devices on a computer network use unique addresses, much like telephone numbers, to
communicate with each other. Each device, depending on its function, will use one or more of
these unique addresses. The addresses correspond to one or more layers of the OSI model. Most
often, network devices use an address at Layer 2 (Data Link Layer) called a MAC address, and
an address at Layer 3 (Network Layer) called a protocol address (for example, IP, IPX, AppleTalk).
One could say that a MAC address is one that is assigned to the hardware, whereas a protocol
address is one that is assigned to the software.
MAC addresses are in the format of 00-00-00-00-00-00 (hexadecimal), IP addresses are in the
format of 0.0.0.0 (dotted decimal), and IPX addresses are in the format of 000000.000000000000
(hexadecimal). Because multiple protocols can reside on the same network device, it is not
uncommon for a single network device to use one MAC address and one or more protocol
addresses.
Ethernet devices communicate directly using the MAC address, not the protocol address. For
instance, when a ping is initiated for the address 1.1.1.1, the network device must find a
corresponding MAC address for the IP address of 1.1.1.1. A frame is then built using the MAC
address that corresponds to 1.1.1.1 and sent to the destination computer. The frame carries the
sender's protocol address in its payload, which is how the destination network device knows to
which device to respond. This means that protocol addresses must be resolved to MAC addresses.
For IP, this is done using ARP (refer to
Communication"
mechanism is needed.
Address – Unicast Versus Broadcast Versus Multicast
There are three types of Layer 2 and Layer 3 addresses: unicast, broadcast, and multicast. A
unicast address is one that corresponds to a single network device, either a single MAC address,
or a single IP address. A broadcast address is one that corresponds to all network devices. A
multicast address is one that corresponds to multiple network devices, but not necessarily all
network devices. When a station transmits a frame to a unicast address, the transmitting device
intends for only a single network device to receive the frame. When a station transmits a frame
to a broadcast MAC address or IP address, the station intends for all devices on a particular
network to receive the frame. When a station transmits a frame to a multicast MAC or IP address,
the station intends for a predefined group of network devices to receive the frame. A group, as
used here, can be defined as more than one network device, but less than all the network devices
on a particular network.
A multicast MAC address is used in HP Integrity Network Adapter Teaming for the purpose of
transmitting and receiving heartbeat frames. Because the heartbeat frames are Layer 2 only frames
(only use MAC addresses), HP Integrity Network adapter teams do not need a protocol address
assigned to them (for example, IP address) for heartbeat frames to function.

Example Scenarios of Network Addressing and Communication

As discussed earlier, protocol addresses (for example, IP, IPX) must be resolved to hardware
addresses (MAC) for network devices to communicate. What follows are two simple scenarios
with one network device (named Red) pinging another network device (named Blue). The first
scenario cites one device pinging another on the same Layer 2 network. The second scenario
cites one device pinging another on a different Layer 2 network, which requires the use of a
router to effect communication.
"Example Scenarios of Network Addressing and
below). For IPX, the MAC address is part of the IPX address, so no special
Layer 2 Versus Layer 3 91