- Mega System Technologies iCAMView Web Server User Manual For models: iCV-01a , iCV-01b, iCV-02, iCV-03

iCAMView user manual -83-

Appendix C: IP Address, Subnet and Gateway

This section discusses Communities, Gateways, IP Addresses and Subnet masking

Communities

A community is a string of printable ASCII characters that identifies a user group with

the same access privileges. For example, a common community name is “public.”

For security purposes, the SNMP agent validates requests before responding. The

agent can be configured so that only trap managers that are members of a community

can send requests and receive responses from a particular community. This

prevents unauthorized managers from viewing or changing the configuration of a

device.

Gateways

Gateway, also referred to as a router, is any computer with two or more network

adapters connecting to different physical networks. Gateways allow for transmission

of IP packets among networks on an Internet.

IP Addresses

Every device on an Internet must be assigned a unique IP (Internet Protocol) address.

An IP address is a 32-bit value comprised of a network ID and a host ID. The

network ID identifies the logical network to which a particular device belongs. The

host ID identifies the particular device within the logical network. IP addresses

distinguish devices on an Internet from one another so that IP packets are properly

transmitted.

IP addresses appear in dotted decimal (rather than in binary) notation. Dotted

decimal notation divides the 32-bit value into four 8-bit groups, or octets, and

separates each octet with a period. For example, 199.217.132.1 is an IP address in

dotted decimal notation.

To accommodate networks of different sizes, the IP address has three divisions –

Classes A for large, B for medium and C for small. The difference among the

network classes is the number of octets reserved for the network ID and the number

of octets reserved for the host ID.

Class Value of First Octet Network ID Host ID Number of Hosts

A 1-126 First octet Last three octets 16,387,064

B 128-191 First two octets Last two octets 64,516

C 192-223 First tree octets Last octet 254

Any value between 0 and 255 is valid as a host ID octet except for those values the

InterNIC reserves for other purposes

Value Purpose

0, 255 Subnet masking

127 Loopback testing and interprocess communication on local devices

224-254 IGMP multicast and other special protocols.