Determining The Subnet Mask; Determining The Address To Use With The Subnet Mask - Cisco 7604 Configuration Manual

Appendix E Addresses, Protocols, and Ports
You can also supernet multiple Class C networks into a larger network by using part of the third octet
for the extended network prefix. For example, 192.168.0.0/20.
This section includes the following topics:
•
•

Determining the Subnet Mask

To determine the subnet mask based on how many hosts you want, see
Table E-1
Hosts
16,777,216
65,536
32,768
16,384
8192
4096
2048
1024
512
256
128
64
32
16
8
4
Do not use
1
1. The first and last number of a subnet are reserved, except for /32, which identifies a single host.

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:
•
•
Catalyst 6500 Series Switch and Cisco 7600 Series Router Firewall Services Module Configuration Guide using ASDM
OL-20748-01
Determining the Subnet Mask, page E-3
Determining the Address to Use with the Subnet Mask, page E-3
Hosts, Bits, and Dotted-Decimal Masks
1
/Bits Mask
/8
/16
/17
/18
/19
/20
/21
/22
/23
/24
/25
/26
/27
/28
/29
/30
/31
/32
Class C-Size Network Address, page E-4
Class B-Size Network Address, page E-4
Dotted-Decimal Mask
255.0.0.0 Class A Network
255.255.0.0 Class B Network
255.255.128.0
255.255.192.0
255.255.224.0
255.255.240.0
255.255.248.0
255.255.252.0
255.255.254.0
255.255.255.0 Class C Network
255.255.255.128
255.255.255.192
255.255.255.224
255.255.255.240
255.255.255.248
255.255.255.252
255.255.255.254
255.255.255.255 Single Host Address
IPv4 Addresses and Subnet Masks
Table E-1.
E-3