User Manual

Appendix B IP Addresses and Subnetting
NBG-418N v2 User’s Guide
166
Configuring IP Addre sse s
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 NBG-418N v2.
Once you have decided on the network number, pick an IP address for your NBG-418N v2 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 NBG-418N v2 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 NBG-418N v2 unless you are instructed to do otherwise.
Private IP Addre sse s
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
3 255.255.224.0 (/19) 8 8190
4 255.255.240.0 (/20) 16 4094
5 255.255.248.0 (/21) 32 2046
6 255.255.252.0 (/22) 64 1022
7 255.255.254.0 (/23) 128 510
8 255.255.255.0 (/24) 256 254
9 255.255.255.128 (/25) 512 126
10 255.255.255.192 (/26) 1024 62
11 255.255.255.224 (/27) 2048 30
12 255.255.255.240 (/28) 4096 14
13 255.255.255.248 (/29) 8192 6
14 255.255.255.252 (/30) 16384 2
15 255.255.255.254 (/31) 32768 1
Table 76 16-bit Network Number Subnet Planning (continued)
NO . “BORROWED”
HO ST BITS
SUBNET MASK NO. SUBNETS
NO . HOSTS PER
SUBNET