Certification Summary

The TCP/IP protocol suite makes the Internet appear to be a big single network to millions of users, even though underneath it is a collection of heterogeneous networks. TCP/IP protocols are organized into five layers that closely correspond to the seven layers of the OSI reference model. Each machine has hardware (MAC) address (defined in the data link layer), which is its identity on a LAN, and an IP address (defined in the network layer) which is its identity on the Internet. Furthermore, a frame (data packet defined in the data link layer) can only be delivered locally, and an IP datagram (a data packet defined in the network layer) can be sent across multiple networks—that is, over the Internet. Each router on the way reframes the datagram as it hops from network to network on its route from source to destination.

You can view the packet traffic on the inbound/outbound connections of your machine by using the netstat command, and if you suspect a problem you can use the ping command to test the reachability of another host. You can also use the snoop command to look into the header of a packet. The packets that you can monitor by using these commands enter or exit through an interface that you can configure by using the ifconfig command.

Once your system is connected to the network through interfaces that you have configured, you need to manage the services running on your system. Standard Internet services are started by inetd at boot time. Solaris 10 offers Services Management Facility (SMF), which augments the traditional UNIX startup scripts and configuration files. The inetadm command is used to manage the inetd controlled services, and svcadm is the SMF utility used to manage the network services.

It's easier to remember a machine on the network by a name rather than by IP address. An entry in the /etc/inet/hosts file on your system contains the following information about a host name associated with your machine: the host name, the corresponding IP address, and an alias for the host name, if any. This file needs entries about other machines on the network only if the network is using the local files for the name service. Usually the network uses the NIS and DNS name services, which maintain host names and addresses on one or more servers. We explore the name services in the next chapter.

Inside the Exam

Comprehend

• The node name of a machine can be found in a file /etc/<nodeName> on the machine, and the host name associated with an interface (specified by <interface>) of the machine can be found in the /etc/hostname.<interface> file.

• Each entry in the /etc/hosts contains the following information about a host: host name, IP address associated with it, and nickname (alias), if any.

• When you enable or disable a network service on your Solaris system by using, say, the svcadm command, the service status change is recorded in the service configuration repository and will persist across reboots.

Look Out

• Because a hardware address is burned into the Ethernet NIC, if you change the Ethernet card, the hardware address of your computer changes.

• Because every IP address has a network component in it, if you move your machine from one network to another, its IP address will change.

• The inetadm command is used to manage inetd-controlled services, whereas svcadm is the SMF command to manage the network services.

Memorize

• The netsat utility is used to view the network packets' activity (statistics) on inbound/outbound connections of your machine.

• The ping command is used to check the reachability of another host on the network (or the Internet).

• The snoop command is used to look into the incoming/outgoing packets on your machine (e.g., the values for the header fields).

• The ifconfig command is used to configure a network interface such as assign an IP address to it, bring it up, or shut it down. You can also use this command to obtain configuration information about an interface.