IP Address Frequently Asked Questions
What is an IP address?
All devices connected to the Internet are identified by a unique IP number. The IP stands for Internet Protocol, which is the name for a standardized identification scheme. It is via IP numbers that different computers on the internet know how to identify each other.
You may know a computer by its name (more correctly its domain name), but names aren't the real way different computers are identified. When you use a browser to surf to a name, somewhere along the communication path, the name is translated into the IP number for that machine. This is done by a Domain Name Server (DNS), which is a computer that has lookup tables for domain names and their relevant IP numbers. When organizations apply for a domain name (such as bcr.org) they are usually assigned a range of IP numbers that they, in turn, assign to the computers within their domain.
What does an IP address look like?
IP numbers take the form of four groups of a maximum of three digits each (called octets) separated by periods (full stops). The periods are usually verbalized as "dot."
Example: 199.045.145.123
This is equivalent to: 199.45.145.123
What is a range of IP addresses?
Any three-digit group (formally referred to as an "octet" because the maximum possible value is 256 unique numbers which is 2 to the eighth power) may have a value ranging from 0 through 255. If your organization "owns" the last three-digit group, a Class C license, then you "own" 256 (0-255) unique IP numbers. A Class B license owns all the numbers in the next to last and last groups. This means that a Class B license has 256 X 256 = 65,536 numbers.
All of these format examples of a Class C license mean the same thing:
199.45.145.0 - 199.45.145.255
199.45.145.0-255
199.45.145.*
What is the difference between static and dynamic IP addressing?
There are actually two ways of assigning IP numbers, static and dynamic. A static IP number is permanently assigned to a computer. Dynamic IP numbers are only assigned to a computer at the time it connects with the Internet. Dynamic IP numbers can change every time the computer reconnects to the Internet. Dynamic IP numbers are used to maximize the use of the numbers available to an organization or an Internet Provider.
What is a proxy server?
A proxy server is a computer that is set up to be the interface between an organization's computers and the Internet. The proxy server's single IP number is the only public access point to the organization from computers outside the organization. The proxy server manages the organization's IP numbers and dynamically assigns them to machines as they are (re)booted. The proxy server also manages the LAN/WAN connectivity for the organization. When communications pass through the proxy server to the Internet, the receiving machine outside the proxy server sees the communication as originating from the proxy server's IP number and uses that IP number to respond. The proxy server keeps track of the dynamically assigned IP numbers "behind" it, and routes communications from the outside to the appropriate computer within the organization.
What is a firewall?
A firewall is a software package that may be part of a proxy server, part of a router or installed on a machine dedicated to the firewall function. It is a method of enhancing an organization's protection from hackers and abusers outside the organization. A firewall can be configured to allow or disallow specific external IP numbers access to the organization's resources. It can also be configured to allow or disallow external users from specific functionalities, such as access to FTP servers, telnet servers, or an organization's intranet.
What is IP filtering?
Many Web-based services can regulate customer access by identifying their customers via the IP number the customer's computer attaches to every message. These services can avoid the inconvenience of requiring the customer to enter a user name and password to gain access. This is extremely useful for services such as online encyclopedias that are purchased for an entire building or campus. Only static IP numbers can be used in this way, although an organization's proxy server IP number can be used to allow access to the entire group of computers served by the proxy server. Of course, if an organization subscribing to a commercial Web service shares a proxy server with nonsubscribers, IP recognition as an access control technology can't be applied. Some proxy servers have the capability of defining subsets of users and assigning a single IP number to a specific subset. When this is possible, IP number filtering is also possible.
What is the effect of a firewall or proxy server?
Some organizations install special security systems on their Internet access called "firewalls" or use "proxy servers." One effect of doing this is that the IP number that is used on individual computers may not be projected onto the Web. Instead the firewall or proxy server acts as a forwarding service and attaches a single IP number to the message that is used on all messages from all of the computers behind the firewall or proxy server. For this reason, it is important to know the IP number of the firewall or proxy server if IP recognition is needed.
The only way a vendor can provide IPnumber recognition/filtering to users behind a proxy server is to turn on the proxy server's number and consequently all computers behind the proxy server. A vendor that you obtain IP filtered access from needs the IP number of the proxy server and an assurance from you that the proxy server only supports computers that are in buildings that are part of the subscription.
There are special reserved IP numbers that are specifically dedicated to LANs behind a proxy server or that are not connected to the Internet at all. These are reserved numbers that are NEVER used as publically accessible addresses on the Internet. The IP number sequences are:
10.0.0.0 (netmask 255.0.0.0)
Any IP# starting with 10. is a fake.
172.16.0.0 - 172.31.0.0 (netmask 255.255.0.0)
Any IP# starting with 172 for the first octet and a value between 16 and 31 (inclusive) for the second octet is a fake.
192.168.0.0 - 192.168.255.0 (netmask 255.255.255.0)
Any IP# with a first octet of 192 and a second octet of 168 is a fake.
If your tech person provides any of the above addresses as your IP number, be advised that these numbers cannot be used for IP number recognition/filtering on the Internet.
How to notify a BCR service provider of IP number changes.
Use the BCR online form.
What is my IP address?
Here is an online service that reports your IP address.
Use this link several times over several days and compare the results. If your IP number changes from connection to connection, you are using dynamic IP numbers and are behind a proxy server.
Use this link from more than one computer while both are booted. If the IP number is the same, you are behind a proxy server.
