HP-UX Reference (11i v2 07/12) - 7 Device (Special) Files, 9 General Information, Index (vol 10)
r
routing(7) routing(7)
Count Destination Type Flags Route Type
Route to a network directly from the local host=0 network
U
Route to a network through a remote host gateway>0 network
UG
Route to a remote host directly from the local host=0 host
UH
Route to a remote host through a remote host gate-
way
>0 host UGH
Wildcard route directly from the local host=0
default U
Wildcard route through a remote host gateway>0
default UG
Subnets
The network facilities support variable-length subnetting. An Internet address is made up of a network
address portion, and a host address portion of an address in the form:
192.34.17.0
Subnet addresses are defined as a portion of the network’s Internet address. This scheme provides for:
• Network addresses that identify physically distinct networks.
• Subnet addresses that identify physically distinct subnetworks of the same network.
A network manager can subdivide the Internet address of the local network into subnets using the host
number space. This facility allows several physical networks to share a single Internet address.
To allow for this, three Internet classes are defined, each accommodating a different amount of network
and host addresses. The address classes are defined by the most significant bit of the binary form of the
address.
The following table lists the number of networks, nodes, and the address ranges for each address class:
Nodes per
Class Networks Network Address Range
A 127 16777215 0.0.0.1 - 127.225.225.254
B 16383 65535 128.0.0.1 - 191.255.255.254
C 2097151 255 192.0.0.1 - 223.244.244.243
Reserved — — 224.0.0.0 - 255.255.255.255
The first 8 bits of a Class A network has network space for only 127, while accommodating the largest
number of nodes possible among the classes defined. A single class B network has the network address lim-
itation of 16 bits, and 16 bits to define the nodes.
For example, a Class C address space is as follows:
______________________________________
Indicates Class C
Class C subnet
networks portion
||
--- ---
10000000.00000110.00000001.11100001
-------------------------- -----
||
Network Address Host
= 192.6.1 Address
=1
______________________________________
A subnet for a given host is specified with the ifconfig command (see ifconfig(1M)), using the netmask
parameter with a 32-bit subnet mask.
The default masks for the three classes of Internet addresses are as follows:
Class A: 255.0.0.0
Class B: 255.255.0.0
Class C: 255.255.255.0
An example Class C network number is 192.34.17.0. The last field specifies the host number. Thus, all
hosts with the prefix 192.34.17 are recognized as being on the same logical and physical network.
140 Hewlett-Packard Company − 3 − HP-UX 11i Version 2: December 2007 Update