
D-1
Cisco PIX Firewall and VPN Configuration Guide
78-15033-01
APPENDIX
D
TCP/IP Reference Information
This appendix includes the following sections:
• IP Addresses, page D-1
• Ports, page D-2
• Protocols and Applications, page D-5
• Using Subnet Masks, page D-7
IP Addresses
• IP address classes are defined as follows:
–
Class A—If the first octet is between 1 and 127 (inclusive), the address is a Class A address. In
a Class A address, the first octet is the one-byte net address and the last three octets are the host
address. The network mask for Class A addresses is 255.0.0.0.
–
Class B—If the first octet is between 128 and 191 (inclusive), the address is a
Class B address. In a Class B address, the first two octets are the net address and the last two
octets are the host address. The network mask for Class B addresses is 255.255.0.0.
–
Class C—If the first octet is 192 or higher, the address is a Class C address. In a
Class C address, the first three octets are the net address and the last octet is the host address.
The network mask for Class C addresses is 255.255.255.0.
–
Class D—These addresses are used for multicast transmissions and within the range from
224.0.0.0 to 239.255.255.255. Some of these addresses are assigned to multicasts used by
specific TCP/IP protocols. Other Class D addresses are assigned to applications, such as
streaming video, that send data to many recipients simultaneously. For information about
enabling the PIX
Firewall to transmit multicast traffic, refer to “Enabling Stub Multicast
Routing” in Chapter 2, “Establishing Connectivity.”
• We recommend that you use RFC 1918 IP addresses for inside and perimeter addresses. These
addresses follow:
–
Class A: 10.0.0.0 to 10.255.255.255
–
Class B: 172.16.0.0 to 172.31.255.255
–
Class C: 192.168.0.0 to 192.168.255.255
–
Class D: 224.0.0.0 to 239.255.255.255
• PIX Firewall requires that IP addresses in the ip address, static, global, failover, and virtual
commands be unique. These IP addresses cannot be the same as your router IP addresses.
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