Determining Host Configuration Modes

As a network administrator, you configure TCP/IP to run on hosts and routers (if applicable). You can configure these machines to obtain configuration information from files on the local machine or from files that are located on other machines on the network. You need the following configuration information:

• Host name of a machine

• IP address of the machine

• Domain name to which the machine belongs

• Default router

• Netmask in use on the machine's network (if applicable)

A machine that obtains TCP/IP configuration information from local files operates in local files mode. A machine that obtains TCP/IP configuration information from a remote machine operates in network client mode.

Machines That Should Run in Local Files Mode

To run in local files mode, a machine must have local copies of the TCP/IP configuration files. TCP/IP Configuration Files describes the files. The machine should have its own disk, though this recommendation is not strictly necessary.

Most servers should run in local file mode. This requirement includes the following servers:

• Network configuration servers

• NFS servers

• Name servers that supply NIS, NIS+, or DNS services

• Mail servers

Additionally, routers should run in local files mode.

Machines that exclusively function as print servers do not need to run in local files mode. Whether individual hosts should run in local files mode depends on the size of your network.

If you are running a very small network, the amount of work that is involved in maintaining these files on individual hosts is manageable. If your network serves hundreds of hosts, the task becomes difficult, even with the network divided into a number of administrative subdomains. Thus, for large networks, using local files mode is usually less efficient. However, because routers and servers must be self-sufficient, they should be configured in local files mode.

Network Configuration Servers

Network configuration servers are the machines that supply the TCP/IP configuration information to hosts that are configured in network client mode. These servers support three booting protocols:

• RARP – Reverse Address Resolution Protocol (RARP) maps Ethernet addresses (48 bits) to IPv4 addresses (32 bits), the reverse of ARP. When you run RARP on a network configuration server, hosts that are running in network client mode obtain their IP addresses and TCP/IP configuration files from the server. The in.rarpd daemon enables RARP services. Refer to the in.rarpd(1M) man page for details.

• TFTP – Trivial File Transfer Protocol (TFTP) is an application that transfers files between remote machines. The in.tftpd daemon executes TFTP services, enabling file transfer between network configuration servers and their network clients. Refer to the in.tftpd(1M) man page for details.

• bootparams – The bootparams protocol supplies parameters for booting that are required by clients that boot off the network. The rpc.bootparamd daemon executes these services. Refer to the bootparamd(1M) man page for details.

Network configuration servers can also function as NFS file servers.

If you are configuring any hosts as network clients, then you must also configure at least one machine on your network as a network configuration server. If your network is subnetted, then you must have at least one network configuration server for each subnet with network clients.

Machines That Are Network Clients

Any host that obtains its configuration information from a network configuration server operates in network client mode. Machines that are configured as network clients do not require local copies of the TCP/IP configuration files.

Network client mode simplifies administration of large networks. Network client mode minimizes the number of configuration tasks that you perform on individual hosts. Network client mode assures that all machines on the network adhere to the same configuration standards.

You can configure network client mode on all types of computers. For example, you can configure network client mode on fully standalone systems or dataless machines.

Mixed Configurations

Configurations are not limited to either an all-local-hosts mode or an all-network-client mode. Routers and servers should always be configured in local mode. For hosts, you can use any combination of local and network client mode.

Sample Network

The following figure shows the hosts of a fictitious network with the network number 192.9.200. The network has one network configuration server, the machine sahara. Machines tenere and nubian have their own disks and run in local files mode. Machine faiyum also has a disk, but this machine operates in network client mode.

Finally, the machine timbuktu is configured as a router. The machine includes two network interfaces. The first interface is named timbuktu. This interface belongs to network 192.9.200. The second interface is named timbuktu-201. This interface belongs to network 192.9.201. Both networks are in the organizational domain deserts.worldwide.com. The domain uses local files as its name service.

Most examples in this chapter use the network that is shown in the following figure.

Figure 4–1 Hosts in a Sample Network