D-3
Cisco Security Appliance Command Line Configuration Guide
OL-12172-03
Appendix D Addresses, Protocols, and Ports
IPv4 Addresses and Subnet Masks
Determining the Subnet Mask
To determine the subnet mask based on how many hosts you want, see
Table D-1
.
Determining the Address to Use with the Subnet Mask
The following sections describe how to determine the network address to use with a subnet mask for a
Class C-size and a Class B-size network. This section includes the following topics:
•
Class C-Size Network Address, page D-3
•
Class B-Size Network Address, page D-4
Class C-Size Network Address
For a network between 2 and 254 hosts, the fourth octet falls on a multiple of the number of host
addresses, starting with 0. For example, the 8-host subnets (/29) of 192.168.0.x are as follows:
Table D-1
Hosts, Bits, and Dotted-Decimal Masks
Hosts
1
1.
The first and last number of a subnet are reserved, except for /32, which identifies a single host.
/Bits Mask
Dotted-Decimal Mask
16,777,216
/8
255.0.0.0 Class A Network
65,536
/16
255.255.0.0 Class B Network
32,768
/17 255.255.128.0
16,384
/18 255.255.192.0
8192
/19
255.255.224.0
4096
/20 255.255.240.0
2048
/21 255.255.248.0
1024
/22 255.255.252.0
512
/23 255.255.254.0
256
/24
255.255.255.0 Class C Network
128
/25 255.255.255.128
64
/26 255.255.255.192
32
/27 255.255.255.224
16
/28 255.255.255.240
8
/29 255.255.255.248
4
/30 255.255.255.252
Do not use
/31
255.255.255.254
1
/32
255.255.255.255 Single Host Address
Subnet with Mask /29 (255.255.255.248)
Address Range
1
192.168.0.0
192.168.0.0 to 192.168.0.7
192.168.0.8
192.168.0.8 to 192.168.0.15
Содержание 500 Series
Страница 38: ...Contents xxxviii Cisco Security Appliance Command Line Configuration Guide OL 12172 03 ...
Страница 45: ...P A R T 1 Getting Started and General Information ...
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Страница 277: ...P A R T 2 Configuring the Firewall ...
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Страница 354: ...17 38 Cisco Security Appliance Command Line Configuration Guide OL 12172 03 Chapter 17 Configuring NAT NAT Examples ...
Страница 561: ...P A R T 3 Configuring VPN ...
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Страница 891: ...P A R T 4 System Administration ...
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Страница 975: ...P A R T 5 Reference ...
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