Appendix B IP Addresses and Subnetting
Table 24
NO. “BORROWED” | SUBNET MASK | NO. SUBNETS | NO. HOSTS PER | |
HOST BITS | SUBNET | |||
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14 | 255.255.255.252 (/30) | 16384 | 2 | |
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15 | 255.255.255.254 (/31) | 32768 | 1 | |
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Configuring IP Addresses
Where you obtain your network number depends on your particular situation. If the ISP or your network administrator assigns you a block of registered IP addresses, follow their instructions in selecting the IP addresses and the subnet mask.
If the ISP did not explicitly give you an IP network number, then most likely you have a single user account and the ISP will assign you a dynamic IP address when the connection is established. If this is the case, it is recommended that you select a network number from 192.168.0.0 to 192.168.255.0. The Internet Assigned Number Authority (IANA) reserved this block of addresses specifically for private use; please do not use any other number unless you are told otherwise. You must also enable Network Address Translation (NAT) on the STB.
Once you have decided on the network number, pick an IP address for your STB that is easy to remember (for instance, 192.168.1.1) but make sure that no other device on your network is using that IP address.
The subnet mask specifies the network number portion of an IP address. Your STB will compute the subnet mask automatically based on the IP address that you entered. You don't need to change the subnet mask computed by the STB unless you are instructed to do otherwise.
Private IP Addresses
Every machine on the Internet must have a unique address. If your networks are isolated from the Internet (running only between two branch offices, for example) you can assign any IP addresses to the hosts without problems. However, the Internet Assigned Numbers Authority (IANA) has reserved the following three blocks of IP addresses specifically for private networks:
•10.0.0.0 — 10.255.255.255
•172.16.0.0 — 172.31.255.255
•192.168.0.0 — 192.168.255.255
You can obtain your IP address from the IANA, from an ISP, or it can be assigned from a private network. If you belong to a small organization and your Internet access is through an ISP, the ISP can provide you with the Internet addresses for your local networks. On the other hand, if you are part of a much larger organization, you should consult your network administrator for the appropriate IP addresses.
Regardless of your particular situation, do not create an arbitrary IP address; always follow the guidelines above. For more information on address assignment, please refer to RFC 1597, Address Allocation for Private Internets and RFC 1466, Guidelines for Management of IP Address Space.
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