Appendix B IP Addresses and Subnetting
311
eir F1000 Modem User
’s Guide
The following figure shows the company network after subnetting. There are now two sub-
networks,
A
and
B
.
Figure 207
Subnetting Example: After Subnetting
In a 25-bit subnet the host ID has 7 bits, so each sub-network has a maximum of 2
7
– 2 or 126
possible hosts (a host ID of all zeroes is the subnet’s address itself, all ones is the subnet’s
broadcast address).
192.168.1.0 with mask 255.255.255.128 is subnet
A
itself, and 192.168.1.127 with mask
255.255.255.128 is its broadcast address. Therefore, the lowest IP address that can be assigned to
an actual host for subnet
A
is 192.168.1.1 and the highest is 192.168.1.126.
Similarly, the host ID range for subnet
B
is 192.168.1.129 to 192.168.1.254.
Example: Four Subnets
The previous example illustrated using a 25-bit subnet mask to divide a 24-bit address into two
subnets. Similarly, to divide a 24-bit address into four subnets, you need to “borrow” two host ID
bits to give four possible combinations (00, 01, 10 and 11). The subnet mask is 26 bits
(11111111.11111111.11111111.
11
000000) or 255.255.255.192.
Each subnet contains 6 host ID bits, giving 2
6
- 2 or 62 hosts for each subnet (a host ID of all
zeroes is the subnet itself, all ones is the subnet’s broadcast address).
Table 132
Subnet 1
IP/SUBNET MASK
NETWORK NUMBER
LAST OCTET BIT
VALUE
IP Address (Decimal)
192.168.1.
0
IP Address (Binary)
11000000.10101000.00000001.
00
000000
Subnet Mask (Binary)
11111111.11111111.11111111.
11
000000
Summary of Contents for eir F1000
Page 4: ...4 eir F1000 Modem User s Guide Contents Overview Diagnostic 273 Troubleshooting 279...
Page 14: ...14 eir F1000 Modem User s Guide Table of Contents...
Page 15: ...PART I User s Guide 15...
Page 16: ...16...
Page 27: ...27 eir F1000 Modem User s Guide Chapter 2 The Web Configurator Figure 10 Connection Status...
Page 33: ...PART II Technical Reference 33...
Page 34: ...34...
Page 68: ...68 eir F1000 Modem User s Guide Chapter 4 Broadband...
Page 134: ...134 eir F1000 Modem User s Guide Chapter 7 Routing...
Page 170: ...170 eir F1000 Modem User s Guide Chapter 9 Network Address Translation NAT...
Page 180: ...Chapter 11 Interface Group 180 eir F1000 Modem User s Guide...
Page 186: ...186 eir F1000 Modem User s Guide Chapter 12 USB Service...
Page 200: ...200 eir F1000 Modem User s Guide Chapter 15 Parental Control...
Page 210: ...210 eir F1000 Modem User s Guide Chapter 17 Certificates...
Page 228: ...Chapter 19 Log 228 eir F1000 Modem User s Guide...
Page 248: ...248 eir F1000 Modem User s Guide Chapter 27 User Account...
Page 252: ...Chapter 28 Remote Management 252 eir F1000 Modem User s Guide...
Page 254: ...254 eir F1000 Modem User s Guide Chapter 29 TR 064...
Page 260: ...Chapter 31 Time Settings 260 eir F1000 Modem User s Guide...
Page 266: ...Chapter 33 Log Setting 266 eir F1000 Modem User s Guide...
Page 272: ...Chapter 35 Configuration 272 eir F1000 Modem User s Guide...
Page 278: ...Chapter 36 Diagnostic 278 eir F1000 Modem User s Guide...
Page 324: ...324 eir F1000 Modem User s Guide Appendix C Pop up Windows JavaScripts and Java Permissions...
Page 338: ...338 eir F1000 Modem User s Guide Appendix D Wireless LANs...