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TCP/IP and IPv4 in Depth (Reference)
This chapter provides TCP/IP network reference information about network configuration files, including the types, their purpose, and the format of the file entries. The existing network databases are also described in detail. The chapter also shows how the structure of IPv4 addresses are derived, based on defined network classifications and subnet numbers.
This chapter contains the following information:
TCP/IP Configuration Files
Each system on the network obtains its TCP/IP configuration information from the following TCP/IP configuration files and network databases:
/etc/hostname.interface file
/etc/nodename file
/etc/defaultdomain file
/etc/defaultrouter file (optional)
hosts database
netmasks database (optional)
The Solaris installation program creates these files as part of the installation process. You can also edit the files manually, as explained in this section. The hosts and netmasks databases are two of the network databases read by the name services available on Solaris networks. Network Databases and the nsswitch.conf File describes in detail the concept of network databases. .
/etc/hostname.interface File
This file defines the physical network interfaces on the local host. At least one /etc/hostname.interface file should exist on the local system. The Solaris installation program creates an /etc/hostname.interface file for the first interface that is found during the installation process. This interface usually has the lowest device number, for example eri0, and is referred to as the primary network interface. If the installation programs finds additional interfaces, you optionally can configure them, as well, as part of the installation process.
If you add a new network interface to your system after installation, you must create an /etc/hostname.interface file for that interface, as explained in How to Configure a Physical Interface After System Installation. Also, for the Solaris software to recognize and use the new network interface, you need to load the interface's device driver into the appropriate directory. Refer to the documentation that comes with the new network interface for the appropriate interface name and device driver instructions.
The basic /etc/hostname.interface file contains one entry: the host name or IPv4 address that is associated with the network interface. The IPv4 address can be expressed in traditional dotted decimal format or in CIDR notation. If you use a host name as the entry for the /etc/hostname.interface file, that host name must also exist in the /etc/inet/hosts file.
For example, suppose smc0 is the primary network interface for a system that is called tenere. The /etc/hostname.smc0 file could have as its entry an IPv4 address in dotted decimal notation or in CIDR notation, or the host name tenere .
Note - IPv6 uses the /etc/hostname6.interface file for defining network interfaces. For more information, refer to IPv6 Interface Configuration File.
/etc/nodename File
This file should contain one entry: the host name of the local system. For example, on system timbuktu, the file /etc/nodename would contain the entry timbuktu.
/etc/defaultdomain File
This file should contain one entry: the fully qualified domain name of the administrative domain to which the local host's network belongs. You can supply this name to the Solaris installation program or edit the file at a later date. For more information on network domains, refer to System Administration Guide: Naming and Directory Services (DNS, NIS, and LDAP).
/etc/defaultrouter File
This file can contain an entry for each router that is directly connected to the network. The entry should be the name for the network interface that functions as a router between networks. The presence of the /etc/defaultrouter file indicates that the system is configured to support static routing.
hosts Database
The hosts database contains the IPv4 addresses and host names of systems on your network. If you use the NIS or DNS name service, or the LDAP directory service, the hosts database is maintained in a database that is designated for host information. For example, on a network that runs NIS, the hosts database is maintained in the hostsbyname file.
If you use local files for the name service, the hosts database is maintained in the /etc/inet/hosts file. This file contains the host names and IPv4 addresses of the primary network interface, other network interfaces that are attached to the system, and any other network addresses that the system must check for.
Note - For compatibility with BSD-based operating systems, the /etc/hosts file is a symbolic link to /etc/inet/hosts.
/etc/inet/hosts File Format
The /etc/inet/hosts file uses the basic syntax that follows. Refer to the hosts(4) man page for complete syntax information.
IPv4-address hostname [nicknames] [#comment]
IPv4-address | Contains the IPv4 address for each interface that the local host must recognize. |
hostname | Contains the host name that is assigned to the system at setup, plus the host names that are assigned to additional network interfaces that the local host must recognize. |
[nickname] | Is an optional field that contains a nickname for the host. |
[#comment] | Is an optional field for a comment. |
Initial /etc/inet/hosts File
When you run the Solaris installation program on a system, the program configures the initial /etc/inet/hosts file. This file contains the minimum entries that the local host requires. The entries include the loopback address, the host IPv4 address, and the host name.
For example, the Solaris installation program might create the following /etc/inet/hosts file for system tenere shown in Figure 5-1:
Example 10-1 /etc/inet/hosts File for System tenere
127.0.0.1 localhost loghost #loopback address 192.168.200.3 tenere #host name |
Loopback Address
In Example 10-1, the IPv4 address 127.0.0.1 is the loopback address. The loopback address is the reserved network interface that is used by the local system to allow interprocess communication. This address enables the host to send packets to itself. The ifconfig command uses the loopback address for configuration and testing, as explained in Monitoring the Interface Configuration With the ifconfig Command. Every system on a TCP/IP network must use the IP address 127.0.0.1 for IPv4 loopback on the local host.
Host Name
The IPv4 address 192.168.200.1 and the name tenere are the address and host name of the local system. They are assigned to the system's primary network interface.
Multiple Network Interfaces
Some systems have more than one network interface, because they are either routers or multihomed hosts. Each network interface that is attached to the system requires its own IP address and associated name. During installation, you must configure the primary network interface. If a particular system has multiple interfaces at installation time, the Solaris installation program also prompts you about these additional interfaces. You can optionally configure one or more additional interfaces at this time, or manually, at a later date.
After Solaris installation, you can configure additional interfaces for a router or multihomed host by adding interface information to the systems' /etc/inet/hosts file. For more information on configuring routers and multihomed hosts refer to Configuring an IPv4 Router and Configuring Multihomed Hosts.
Example 10-2 shows the /etc/inet/hosts file for system timbuktu that is shown in Figure 5-1.
Example 10-2 /etc/inet/hosts File for System timbuktu
127.0.0.1 localhost loghost 192.168.200.70 timbuktu #This is the local host name 192.168.201.10 timbuktu-201 #Interface to network 192.9.201 |
With these two interfaces, timbuktu connects networks 192.168.200 and 192.168.201 as a router.