INSTALLATION
Private Subnets
There are three IP network addresses reserved for private networks. The addresses are 10.0.0.0,
Subnet Mask 255.0.0.0, 172.16.0.0, Subnet Mask 255.240.0.0, and 192.168.0.0, Subnet Mask
255.255.0.0. These addresses are also notated 10.0.0.0/8, 172.16.0.0/12, and
192.168.0.0/16;. They can be used by anyone setting up internal IP networks, such as a lab or home
LAN behind a NAT or proxy server or a router. It is always safe to use these because routers on the
Internet by default will never forward packets coming from these addresses.
Subnetting an IP Network can be done for a variety of reasons, including organization, use
of different physical media (such as Ethernet, FDDI, WAN, etc.), preservation of address space,
and security. The most common reason is to control network traffic. In an Ethernet network, all
nodes on a segment see all the packets transmitted by all the other nodes on that segment.
Performance can be adversely affected under heavy traffic loads, due to collisions and the
resulting retransmissions. A router is used to connect IP networks to minimize the amount of
traffic each segment must receive.
Subnet Masking
Applying a subnet mask to an IP address allows you to identify the network and node parts of
the address. The network bits are represented by the “1”s in the mask, and the node bits are
represented by the “0”s. Performing a bitwise logical AND operation between the IP address and
the subnet mask results in the Network Address or Number.
For example, using our test IP address and the default Class B subnet mask, we get:
10001100.00011010.11110000.11001000 172.26.240.200
Class B IP Address
11111111.11111111.00000000.00000000 255.255.000.000 Default Class B Subnet Mask
10001100.00011010.00000000.00000000 172.26.000.000 Network Address
Default subnet masks:
•
Class A - 255.0.0.0 -11111111.00000000.00000000.00000000
•
Class B - 255.255.0.0 -11111111.11111111.00000000.00000000
•
Class C - 255.255.255.0 - 11111111.11111111.11111111.00000000
MAC Address
In networking, the Media Access Control (MAC) address is a unique identifier programmed into
each network device. This number acts like a name for a the device, and all SpeedNet Radios
have unique MAC addresses. Some devices have user configurable MAC addresses, but the
SpeedNet Radio MAC address is configured at the factory and cannot be changed. Most protocols
use MAC addresses that are globally unique, but not all protocols use MAC addresses, or require
that they be unique.
Unlike IP
addresses, MAC addresses do not have node and Network sections, and a
receiving node cannot determine any network information from the MAC address. The length of a
MAC address is 6 bytes and an IP address is 4 bytes long, therefore the MAC address cannot be
represented using an IP address. So an IP address must be mapped to its corresponding MAC
address. Address Restoration Protocol (ARP) is used to locate a specific MAC address. ARP
broadcasts an ARP request packet, which contains the source MAC address, the source IP
address, and the destination IP address. Each node in the local network receives this packet. A
node that has the specified destination IP address, returns an ARP reply packet with its IP address
to the originating host. Eventually the path will extend to the destination IP address, and that
device will return the ARP packet that includes its MAC address.
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