Every computer on the Internet has a unique 32-bit address. These 32 bits (or 4 bytes) are normally written as illustrated in the second row in Example 30.1, “Writing IP Addresses”.

IP Address (binary):  11000000 10101000 00000000 00010100
IP Address (decimal):      192.     168.       0.      20

In decimal form, the four bytes are written in the decimal number system, separated by periods. The IP address is assigned to a host or a network interface. It cannot be used anywhere else in the world. There are exceptions to this rule, but these are not relevant in the following passages.

The points in IP addresses indicate the hierarchical system. Until the 1990s, IP addresses were strictly categorized in classes. However, this system has proven too inflexible and was discontinued. Now, classless routing (CIDR, classless interdomain routing) is used.

Netmasks are used to define the address range of a subnetwork. If two hosts are in the same subnetwork, they can reach each other directly, if they are not in the same subnetwork, they need the address of a gateway that handles all the traffic between the subnetwork and the rest of the world. To check if two IP addresses are in the same subnet, simply “AND” both addresses with the netmask. If the result is identical, both IP addresses are in the same local network. If there are differences, the remote IP address, and thus the remote interface, can only be reached over a gateway.

To understand how the netmask works, look at Example 30.2, “Linking IP Addresses to the Netmask”. The netmask consists of 32 bits that identify how much of an IP address belongs to the network. All those bits that are 1 mark the corresponding bit in the IP address as belonging to the network. All bits that are 0 mark bits inside the subnetwork. This means that the more bits are 1, the smaller the subnetwork is. Because the netmask always consists of several successive 1 bits, it is also possible to just count the number of bits in the netmask. In Example 30.2, “Linking IP Addresses to the Netmask” the first net with 24 bits could also be written as 192.168.0.0/24.

IP address (192.168.0.20):  11000000 10101000 00000000 00010100
Netmask   (255.255.255.0):  11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link:         11000000 10101000 00000000 00000000
In the decimal system:           192.     168.       0.       0

IP address (213.95.15.200): 11010101 10111111 00001111 11001000
Netmask    (255.255.255.0): 11111111 11111111 11111111 00000000
---------------------------------------------------------------
Result of the link:         11010101 10111111 00001111 00000000
In the decimal system:           213.      95.      15.       0

To give another example: all machines connected with the same ethernet cable are usually located in the same subnetwork and are directly accessible. Even when the subnet is physically divided by switches or bridges, these hosts can still be reached directly.

IP addresses outside the local subnet can only be reached if a gateway is configured for the target network. In the most common case, there is only one gateway that handles all traffic that is external. However, it is also possible to configure several gateways for different subnets.

If a gateway has been configured, all external IP packets are sent to the appropriate gateway. This gateway then attempts to forward the packets in the same manner—from host to host—until it reaches the destination host or the packet's TTL (time to live) expires.

Because IP addresses must be unique all over the world, you cannot just select random addresses. There are three address domains to use if you want to set up a private IP-based network. These cannot get any connection from the rest of the Internet, because they cannot be transmitted over the Internet. These address domains are specified in RFC 1597 and listed in Table 30.3, “Private IP Address Domains”.

The most important and most visible improvement brought by the new protocol is the enormous expansion of the available address space. An IPv6 address is made up of 128 bit values instead of the traditional 32 bits. This provides for as many as several quadrillion IP addresses.

However, IPv6 addresses are not only different from their predecessors with regard to their length. They also have a different internal structure that may contain more specific information about the systems and the networks to which they belong. More details about this are found in Section 30.2.2, “Address Types and Structure”.

The following is a list of some other advantages of the new protocol:

As mentioned, the current IP protocol is lacking in two important aspects: there is an increasing shortage of IP addresses and configuring the network and maintaining the routing tables is becoming a more complex and burdensome task. IPv6 solves the first problem by expanding the address space to 128 bits. The second one is countered by introducing a hierarchical address structure, combined with sophisticated techniques to allocate network addresses, as well as multihoming (the ability to assign several addresses to one device, giving access to several networks).

When dealing with IPv6, it is useful to know about three different types of addresses:

An IPv6 address is made up of eight four-digit fields, each representing 16 bits, written in hexadecimal notation. They are also separated by colons (:). Any leading zero bytes within a given field may be dropped, but zeros within the field or at its end may not. Another convention is that more than four consecutive zero bytes may be collapsed into a double colon. However, only one such :: is allowed per address. This kind of shorthand notation is shown in Example 30.3, “Sample IPv6 Address”, where all three lines represent the same address.

fe80 : 0000 : 0000 : 0000 : 0000 : 10 : 1000 : 1a4
fe80 :    0 :    0 :    0 :    0 : 10 : 1000 : 1a4
fe80 :                           : 10 : 1000 : 1a4

Each part of an IPv6 address has a defined function. The first bytes form the prefix and specify the type of address. The center part is the network portion of the address, but it may be unused. The end of the address forms the host part. With IPv6, the netmask is defined by indicating the length of the prefix after a slash at the end of the address. An address, as shown in Example 30.4, “IPv6 Address Specifying the Prefix Length”, contains the information that the first 64 bits form the network part of the address and the last 64 form its host part. In other words, the 64 means that the netmask is filled with 64 1-bit values from the left. Just like with IPv4, the IP address is combined with AND with the values from the netmask to determine whether the host is located in the same subnetwork or in another one.

fe80::10:1000:1a4/64

IPv6 knows about several predefined types of prefixes. Some of these are shown in Table 30.4, “Various IPv6 Prefixes”.

A unicast address consists of three basic components:

On top of this basic structure, IPv6 distinguishes between five different types of unicast addresses:

As a completely new feature introduced with IPv6, each network interface normally gets several IP addresses, with the advantage that several networks can be accessed through the same interface. One of these networks can be configured completely automatically using the MAC and a known prefix with the result that all hosts on the local network can be reached as soon as IPv6 is enabled (using the link-local address). With the MAC forming part of it, any IP address used in the world is unique. The only variable parts of the address are those specifying the site topology and the public topology, depending on the actual network in which the host is currently operating.

For a host to go back and forth between different networks, it needs at least two addresses. One of them, the home address, not only contains the interface ID but also an identifier of the home network to which it normally belongs (and the corresponding prefix). The home address is a static address and, as such, it does not normally change. Still, all packets destined to the mobile host can be delivered to it, regardless of whether it operates in the home network or somewhere outside. This is made possible by the completely new features introduced with IPv6, such as stateless autoconfiguration and neighbor discovery. In addition to its home address, a mobile host gets one or more additional addresses that belong to the foreign networks where it is roaming. These are called care-of addresses. The home network has a facility that forwards any packets destined to the host when it is roaming outside. In an IPv6 environment, this task is performed by the home agent, which takes all packets destined to the home address and relays them through a tunnel. On the other hand, those packets destined to the care-of address are directly transferred to the mobile host without any special detours.

The migration of all hosts connected to the Internet from IPv4 to IPv6 is a gradual process. Both protocols will coexist for some time to come. The coexistence on one system is guaranteed where there is a dual stack implementation of both protocols. That still leaves the question of how an IPv6 enabled host should communicate with an IPv4 host and how IPv6 packets should be transported by the current networks, which are predominantly IPv4 based. The best solutions offer tunneling and compatibility addresses (see Section 30.2.2, “Address Types and Structure”).

IPv6 hosts that are more or less isolated in the (worldwide) IPv4 network can communicate through tunnels: IPv6 packets are encapsulated as IPv4 packets to move them across an IPv4 network. Such a connection between two IPv4 hosts is called a tunnel. To achieve this, packets must include the IPv6 destination address (or the corresponding prefix) as well as the IPv4 address of the remote host at the receiving end of the tunnel. A basic tunnel can be configured manually according to an agreement between the hosts' administrators. This is also called static tunneling.

However, the configuration and maintenance of static tunnels is often too labor-intensive to use them for daily communication needs. Therefore, IPv6 provides for three different methods of dynamic tunneling:

To configure IPv6, you do not normally need to make any changes on the individual workstations. IPv6 is enabled by default. You can disable it during installation in the network configuration step described in Section 3.14.3, “Network Configuration”. To disable or enable IPv6 on an installed system, use YaST Network Card. Do not change the method and click Next. Then select a card and click Advanced+IPv6 in the Address tab. To enable IPv6 manually, enter modprobe ipv6 as root.

Because of the autoconfiguration concept of IPv6, the network card is assigned an address in the link-local network. Normally, no routing table management takes place on a workstation. The network routers can be queried by the workstation, using the router advertisement protocol, for what prefix and gateways should be implemented. The radvd program can be used to set up an IPv6 router. This program informs the workstations which prefix to use for the IPv6 addresses and which routers. Alternatively, use zebra for automatic configuration of both addresses and routing.

Consult the ifup(8) man page to get information about how to set up various types of tunnels using the /etc/sysconfig/network files.

The above overview does not cover the topic of IPv6 comprehensively. For a more in-depth look at the new protocol, refer to the following online documentation and books:

To configure your network wired or wireless card in YaST, select Network Devices+Network Card. After starting the module, YaST displays a general network configuration dialog. Choose whether to use YaST or NetworkManager to manage all your network devices. If you want to configure your network in the traditional way with the YaST, check Traditional Method with ifup and click Next. To use NetworkManager, check User Controlled with NetworkManager and click Next. Find detailed information about NetworkManager in Section 30.6, “Managing Network Connections with NetworkManager”.

	Network Method and Xen
NetworkManager does not work with Xen. Only Traditional Method with ifup is available in Xen.

The upper part of the next dialog shows a list with all the network cards available for configuration. Any card properly detected is listed with its name. To change the configuration of the selected device, click Edit. Devices that could not be detected can be configured using Add as described in Section 30.4.1.2, “Configuring an Undetected Network Card”.

Figure 30.3. Configuring a Network Card¶

30.4.1.1. Changing the Configuration of a Network Card¶

To change the configuration of a network card, select a card from the list of the detected cards in the YaST network card configuration module and click Edit. The Network Address Setup dialog appears in which to adjust the card configuration using the Address and General tabs. For information about wireless card configuration, see Section 29.1.3, “Configuration with YaST”.

30.4.1.1.1. Configuring IP Addresses¶

When possible, wired network cards available during installation are automatically configured to use automatic address setup, DHCP.

	IBM System z and DHCP
On IBM System z platforms, DHCP-based address configuration is only supported with network cards that have a MAC address. This is only the case with OSA and OSA Express cards.

DHCP should also be used for a DSL line with no static IP assigned by the ISP. If you decide to use DHCP, configure the details in DHCP Client Options. Find this dialog from the Address tab by selecting Advanced+DHCP Options. Specify whether the DHCP server should always honor broadcast requests and any identifier to use. If you have a virtual host setup where different hosts communicate through the same interface, an identifier is necessary to distinguish them.

DHCP is a good choice for client configuration but it is not ideal for server configuration. To set a static IP address, proceed as follows:

1. Select a card from the list of detected cards in the YaST network card configuration module and click Edit.

2. In the Address tab, choose Static Address Setup.

3. Enter IP Address and Subnet Mask.

4. Click Next.

5. To activate the configuration, click Finish.

If you use the static address, name servers and a default gateway are not configured automatically. To configure a gateway, click Routing and add the default gateway. To configure name servers, click Hostname and Name Server and add addresses of name servers and domains.

30.4.1.1.2. Configuring Aliases¶

One network device can have multiple IP addresses, called aliases. To set an alias for your network card, proceed as follows:

1. Select a card from the list of detected cards in the YaST network card configuration module and click Edit.

2. In the Address tab, choose Advanced+Additional Addresses.

3. Click Add.

4. Enter Alias Name, IP Address, and Netmask.

5. Click OK.

6. Click OK again.

7. Click Next.

8. To activate the configuration, click Finish.

30.4.1.1.3. Configuring Hostname and DNS¶

If you did not change the network configuration during installation and the wired card was available, a hostname was automatically generated for your computer and DHCP was activated. The same applies to the name service information your host needs to integrate into a network environment. If DHCP is used for network address setup, the list of domain name servers is automatically filled with the appropriate data. If a static setup is preferred, set these values manually.

To change the name of your computer and adjust the name server search list, proceed as follows:

1. Select a card from the list of detected cards in the YaST network card configuration module and click Edit.

2. In the Address tab, click Hostname and Name Server.

3. To disable DHCP-driven host name configuration, deselect Change Hostname via DHCP.

4. Enter Hostname and, if it is needed, Domain Name.

5. To disable DHCP driven updates of the name server list, deselect Update Name Servers and Search List via DHCP.

6. Enter the name servers and domain search list.

7. Click OK.

8. Click Next.

9. To activate the configuration, click Finish.

30.4.1.1.4. Configuring Routing¶

To make your machine communicate with other machines and other networks, routing information must be given to make network traffic take the correct path. If DHCP is used, this information is automatically provided. If a static setup is used, this data must be added manually.

1. Select a card from the list of detected cards in the YaST network card configuration module and click Edit.

2. In the Address tab, click Routing.

3. Enter the IP of the Default Gateway.

4. Click OK.

5. Click Next.

6. To activate the configuration, click Finish.

30.4.1.1.5. Adding Special Hardware Options¶

Sometimes a module of a network card needs special parameters to work correctly. To set them with YaST, proceed as follows:

1. Select a card from the list of detected cards in the YaST network card configuration module and click Edit.

2. In the Address tab, click Advanced+Hardware Details.

3. In Options, enter the parameters for your network card. If two cards are configured that use the same module, these parameters are used for both.

4. Click OK.

5. Click Next.

6. To activate configuration, click Finish.

30.4.1.1.6. Starting the Device¶

If you use the traditional method with ifup, you can configure your device to start during boot, on cable connection, on card detection, manually, or never. To change device start-up, proceed as follows:

1. Select a card from the list of detected cards in the YaST network card configuration module and click Edit.

2. In the General tab, select the desired entry from Device Activation.

3. Click Next.

4. To activate the configuration, click Finish.

30.4.1.1.7. Configuring the Firewall¶

Without having to enter the detailed firewall setup as described in Section 43.4.1, “Configuring the Firewall with YaST”, you can determine the basic firewall setup for your device as part of the device setup. Proceed as follows:

1. Select a card from the list of detected cards in the YaST network card configuration module and click Edit.

2. Enter the General tab of the network configuration dialog.

3. Determine the firewall zone to which your interface should be assigned. The following options are available:

   No Zone, All Traffic Blocked

   All traffic will be blocked for this interface.

   Internal Zone (Unprotected)

   The firewall is run, but does not enforce any rules to protect this interface. Only use this option, if your machine is part of a greater network that is protected by an outer firewall.

   Demilitarized Zone

   A demilitarized zone is an additional line of defense in front of an internal network and the (hostile) Internet. Hosts assigned to this zone can be reached from the internal network and from the Internet, but cannot access the internal network.

   External Zone

   The firewall is run on this interface and fully protects it against other (presumably hostile) network traffic. This is the default option.

4. Click Next.

5. Activate the configuration by clicking Finish.

	IBM System z: Modem
The configuration of this type of hardware is not supported on IBM System z platforms.

In the YaST Control Center, access the modem configuration with Network Devices+Modem. If your modem was not automatically detected, open the dialog for manual configuration by clicking Add. In the dialog that opens, enter the interface to which the modem is connected for Modem Device.

	CDMA and GPRS Modems
Configure supported CDMA and GPRS modems with the YaST modem module just as you would configure regular modems.

Figure 30.4. Modem Configuration¶

If behind a private branch exchange (PBX), you may need to enter a dial prefix. This is often a zero. Consult the instructions that came with the PBX to find out. Also select whether to use tone or pulse dialing, whether the speaker should be on, and whether the modem should wait until it detects a dial tone. The last option should not be enabled if the modem is connected to an exchange.

Under Details, set the baud rate and the modem initialization strings. Only change these settings if your modem was not detected automatically or if it requires special settings for data transmission to work. This is mainly the case with ISDN terminal adapters. Leave this dialog by clicking OK. To delegate control over the modem to the normal user without root permissions, activate User Controlled. In this way, a user without administrator permissions can activate or deactivate an interface. Under Dial Prefix Regular Expression, specify a regular expression. The Dial Prefix in KInternet, which can be modified by the normal user, must match this regular expression. If this field is left empty, the user cannot set a different Dial Prefix without administrator permissions.

In the next dialog, select the ISP (Internet service provider). To choose from a predefined list of ISPs operating in your country, select Country. Alternatively, click New to open a dialog in which to provide the data for your ISP. This includes a name for the dial-up connection and ISP as well as the login and password provided by your ISP. Enable Always Ask for Password to be prompted for the password each time you connect.

In the last dialog, specify additional connection options:

Selecting Next returns to the original dialog, which displays a summary of the modem configuration. Close this dialog with Finish.

	IBM System z: ISDN
The configuration of this type of hardware is not supported on IBM System z platforms.

Use this module to configure one or several ISDN cards for your system. If YaST did not detect your ISDN card, click Add and manually select it. Multiple interfaces are possible, but several ISPs can be configured for one interface. In the subsequent dialogs, set the ISDN options necessary for the proper functioning of the card.

Figure 30.5. ISDN Configuration¶

In the next dialog, shown in Figure 30.5, “ISDN Configuration”, select the protocol to use. The default is Euro-ISDN (EDSS1), but for older or larger exchanges, select 1TR6. If you are in the US, select NI1. Select your country in the relevant field. The corresponding country code then appears in the field next to it. Finally, provide your Area Code and the Dial Prefix if necessary.

Device Activation defines how the ISDN interface should be started: At Boot Time causes the ISDN driver to be initialized each time the system boots. Manually requires you to load the ISDN driver as root with the command rcisdn start. On Hotplug, used for PCMCIA or USB devices, loads the driver after the device is plugged in. When finished with these settings, select OK.

In the next dialog, specify the interface type for your ISDN card and add ISPs to an existing interface. Interfaces may be either the SyncPPP or the RawIP type, but most ISPs operate in the SyncPPP mode, which is described below.

Figure 30.6. ISDN Interface Configuration¶

The number to enter for My Phone Number depends on your particular setup:

For the connection to be terminated just before the next charge unit is due, enable ChargeHUP. However, remember that may not work with every ISP. You can also enable channel bundling (multilink PPP) by selecting the corresponding option. Finally, you can enable SuSEfirewall2 for your link by selecting External Firewall Interface and Restart Firewall. To enable the normal user without administrator permissions to activate or deactivate the interface, select the User Controlled.

Details opens a dialog in which to configure callback mode, remote connections to this interface and additional ippd options. Leave the Details dialog by selecting OK.

In the next dialog, make IP address settings. If you have not been given a static IP by your provider, select Dynamic IP Address. Otherwise, use the fields provided to enter your host's local IP address and the remote IP address according to the specifications of your ISP. If the interface should be the default route to the Internet, select Default Route. Each host can only have one interface configured as the default route. Leave this dialog by selecting Next.

The following dialog allows you to set your country and select an ISP. The ISPs included in the list are call-by-call providers only. If your ISP is not in the list, select New. This opens the Provider Parameters dialog in which to enter all the details for your ISP. When entering the phone number, do not include any blanks or commas among the digits. Finally, enter your login and the password as provided by the ISP. When finished, select Next.

To use Dial on Demand on a stand-alone workstation, also specify the name server (DNS server). Most ISPs support dynamic DNS, which means the IP address of a name server is sent by the ISP each time you connect. For a single workstation, however, you still need to provide a placeholder address like 192.168.22.99. If your ISP does not support dynamic DNS, specify the name server IP addresses of the ISP. If desired, specify a time-out for the connection—the period of network inactivity (in seconds) after which the connection should be automatically terminated. Confirm your settings with Next. YaST displays a summary of the configured interfaces. To make all these settings active, select Finish.

	IBM System z: Cable Modem
The configuration of this type of hardware is not supported on IBM System z platforms.

In some countries, such as Austria and the US, it is quite common to access the Internet through the TV cable network. The TV cable subscriber usually gets a modem that is connected to the TV cable outlet on one side and to a computer network card on the other (using a 10Base-TG twisted pair cable). The cable modem then provides a dedicated Internet connection with a fixed IP address.

Depending on the instructions provided by your ISP, when configuring the network card either select Automatic Address Setup (via DHCP) or Static Address Setup. Most providers today use DHCP. A static IP address often comes as part of a special business account.

For further information about the configuration of cable modems, read the Support Database article on the topic, which is available online at http://old-en.opensuse.org/SDB:Setting_Up_an_Internet_Connection_via_Cable_Modem_with_SuSE_Linux_8.0_or_Higher.

	IBM System z: DSL
The configuration of this type of hardware is not supported on IBM System z platforms.

To configure your DSL device, select the DSL module from the YaST Network Devices section. This YaST module consists of several dialogs in which to set the parameters of DSL links based on one of the following protocols:

The configuration of a DSL connection based on PPPoE or PPTP requires that the corresponding network card has already been set up in the correct way. If you have not done so yet, first configure the card by selecting Configure Network Cards (see Section 30.4.1, “Configuring the Network Card with YaST”). In the case of a DSL link, addresses may be assigned automatically but not via DHCP, which is why you should not enable the option Automatic address setup (via DHCP). Instead, enter a static dummy address for the interface, such as 192.168.22.1. In Subnet Mask, enter 255.255.255.0. If you are configuring a stand-alone workstation, leave Default Gateway empty.

Values in IP Address and Subnet Mask are only placeholders. They are only needed to initialize the network card and do not represent the DSL link as such.

Figure 30.7. DSL Configuration¶

To begin the DSL configuration (see Figure 30.7, “DSL Configuration”), first select the PPP mode and the ethernet card to which the DSL modem is connected (in most cases, this is eth0). Then use Device Activation to specify whether the DSL link should be established during the boot process. Click User Controlled to authorize the normal user without root permissions to activate or deactivate the interface with KInternet. The dialog also lets you select your country and choose from a number of ISPs operating in it. The details of any subsequent dialogs of the DSL configuration depend on the options set so far, which is why they are only briefly mentioned in the following paragraphs. For details on the available options, read the detailed help available from the dialogs.

To use Dial on Demand on a stand-alone workstation, also specify the name server (DNS server). Most ISPs support dynamic DNS—the IP address of a name server is sent by the ISP each time you connect. For a single workstation, however, provide a placeholder address like 192.168.22.99. If your ISP does not support dynamic DNS, enter the name server IP address provided by your ISP.

Idle Time-Out (seconds) defines a period of network inactivity after which to terminate the connection automatically. A reasonable time-out value is between 60 and 300 seconds. If Dial on Demand is disabled, it may be useful to set the time-out to zero to prevent automatic hang-up.

The configuration of T-DSL is very similar to the DSL setup. Just select T-Online as your provider and YaST opens the T-DSL configuration dialog. In this dialog, provide some additional information required for T-DSL—the line ID, the T-Online number, the user code, and your password. All of these should be included in the information you received after subscribing to T-DSL.

SUSE Linux Enterprise for IBM System z supports several different types of network interfaces. YaST can be used to configure all of them.

30.4.6.3. The ctc Device¶

To add a ctc (IBM parallel CTC Adapter) interface to the installed system, start the YaST network card module (Network Devices+Network Card). Select one of the devices marked IBM parallel CTC Adapter to use as your read channel and click Configure. Choose the Device Settings that fit your devices (usually this would be Compatibility mode). Specify both your IP address and the IP address of the remote partner. If needed, adjust the MTU size with Advanced+Detailed Settings. Leave the network configuration with Next and Finish.

The use of this interface is deprecated. This interface will not be supported in future versions of SUSE Linux Enterprise.

30.4.6.5. The IUCV Device¶

To add an iucv (IUCV) interface to the installed system, start the YaST network card module (Network Devices+Network Card). Select a device marked IUCV and click Configure. YaST prompts you for the name of your IUCV partner. Enter the name (this entry is case-sensitive) and select Next. Specify both your IP address and the IP address of your partner. If needed, adjust the MTU size with Advanced+Detailed Settings. Leave the network configuration with Next and Finish.

The use of this interface is deprecated. This interface will not be supported in future versions of SUSE Linux Enterprise.

If you use NetworkManager for network setup, you can easily switch, stop, or start your network connection at any time from within your desktop environment using an applet. NetworkManager also makes it possible to change and configure wireless card connections without requiring root privileges. For this reason, NetworkManager is the ideal solution for a mobile workstation.

Traditional configuration with ifup also provides some ways to switch, stop, or start the connection with or without user intervention, like user-managed devices, but it always requires root privileges to change or configure a network device. This is often a problem for mobile computing, where is not possible to preconfigure all connection possibilities.

Both traditional configuration and NetworkManager can handle network connections with a wireless network (with WEP, WPA-PSK, and WPA-Enterprise access), dial-up, and wired networks both using DHCP and static configuration. They also support connection through VPN.

NetworkManager tries to keep your computer connected at all times using the best connection available. If available, it uses the fastest wired connection. If the network cable is accidentally disconnected, it tries to reconnect. It can find a network with the best signal strength from the list of your wireless connections and automatically use it to connect. To get the same functionality with ifup, a great deal of configuration effort is required.

Find more information about NetworkManager on the following Web sites and directories:

This section provides an overview of the network configuration files and explains their purpose and the format used.

# Destination     Dummy/Gateway     Netmask            Device
#
127.0.0.0         0.0.0.0           255.255.255.0      lo
204.127.235.0     0.0.0.0           255.255.255.0      eth0
default           204.127.235.41    0.0.0.0            eth0
207.68.156.51     207.68.145.45     255.255.255.255    eth1
192.168.0.0       207.68.156.51     255.255.0.0        eth1

# Our domain
search example.com
#
# We use sun (192.168.0.20) as nameserver
nameserver 192.168.0.20

127.0.0.1 localhost
192.168.0.20 sun.example.com sun
192.168.0.1 earth.example.com earth

loopback     127.0.0.0
localnet     192.168.0.0

# We have named running
order hosts bind
# Allow multiple addrs
multi on

passwd:     compat
group:      compat

hosts:      files dns
networks:   files dns

services:   db files
protocols:  db files

netgroup:   files
automount:  files nis

Before you write your configuration to the configuration files, you can test it. To set up a test configuration, use the ip command. To test the connection, use the ping command. Older configuration tools, ifconfig and route, are also available.

The commands ip, ifconfig, and route change the network configuration directly without saving it in the configuration file. Unless you enter your configuration in the correct configuration files, the changed network configuration is lost on reboot.

ping -c 3 example.com
PING example.com (130.57.5.75) 56(84) bytes of data.
64 bytes from example.com (130.57.5.75): icmp_seq=1 ttl=49 time=188 ms
64 bytes from example.com (130.57.5.75): icmp_seq=2 ttl=49 time=184 ms
64 bytes from example.com (130.57.5.75): icmp_seq=3 ttl=49 time=183 ms
--- example.com ping statistics ---
3 packets transmitted, 3 received, 0% packet loss, time 2007ms
rtt min/avg/max/mdev = 183.417/185.447/188.259/2.052 ms

30.7.2.3. Configuring the Network with ifconfig¶

ifconfig is a traditional network configuration tool. In contrast to ip, you can use it only for interface configuration. If you want to configure routing, use route.

	ifconfig and ip
The program ifconfig is obsolete. Use ip instead.

Without arguments, ifconfig displays the status of the currently active interfaces. As you can see in Example 30.11, “Output of the ifconfig Command”, ifconfig has very well-arranged and detailed output. The output also contains information about the MAC address of your device, the value of HWaddr, in the first line.

Example 30.11. Output of the ifconfig Command¶

eth0      Link encap:Ethernet  HWaddr 00:08:74:98:ED:51
          inet6 addr: fe80::208:74ff:fe98:ed51/64 Scope:Link
          UP BROADCAST MULTICAST  MTU:1500  Metric:1
          RX packets:634735 errors:0 dropped:0 overruns:4 frame:0
          TX packets:154779 errors:0 dropped:0 overruns:0 carrier:1
          collisions:0 txqueuelen:1000
          RX bytes:162531992 (155.0 Mb)  TX bytes:49575995 (47.2 Mb)
          Interrupt:11 Base address:0xec80
      
lo        Link encap:Local Loopback
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:16436  Metric:1
          RX packets:8559 errors:0 dropped:0 overruns:0 frame:0
          TX packets:8559 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:0
          RX bytes:533234 (520.7 Kb)  TX bytes:533234 (520.7 Kb)    
      
wlan1     Link encap:Ethernet  HWaddr 00:0E:2E:52:3B:1D
          inet addr:192.168.2.4  Bcast:192.168.2.255  Mask:255.255.255.0
          inet6 addr: fe80::20e:2eff:fe52:3b1d/64 Scope:Link
          UP BROADCAST NOTRAILERS RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:50828 errors:0 dropped:0 overruns:0 frame:0
          TX packets:43770 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000
          RX bytes:45978185 (43.8 Mb)  TX bytes:7526693 (7.1 Mb)

For more options and information about using ifconfig, enter ifconfig -h or see the ifconfig (8) man page.

30.7.2.4. Configuring Routing with route¶

route is a program for manipulating the IP routing table. You can use it to view your routing configuration and add or remove of routes.

	route and ip
The program route is obsolete. Use ip instead.

route is especially useful if you need quick and comprehensible information about your routing configuration to determine problems with routing. To view your current routing configuration, enter route -n as root.

Example 30.12. Output of the route -n Command¶

route -n
Kernel IP routing table
Destination     Gateway         Genmask         Flags   MSS Window  irtt Iface
10.20.0.0       *               255.255.248.0   U         0 0          0 eth0
link-local      *               255.255.0.0     U         0 0          0 eth0
loopback        *               255.0.0.0       U         0 0          0 lo
default         styx.exam.com   0.0.0.0         UG        0 0          0 eth0

For more options and information about using route, enter route -h or see the route (8) man page.

Apart from the configuration files described above, there are also various scripts that load the network programs while the machine is booting. These are started as soon as the system is switched to one of the multiuser runlevels. Some of these scripts are described in Table 30.9, “Some Start-Up Scripts for Network Programs”.

The connections provided by smpppd are automatically configured by YaST. The actual dial-up programs KInternet and cinternet are also preconfigured. Manual settings are only required to configure additional features of smpppd, such as remote control.

The configuration file of smpppd is /etc/smpppd.conf. By default, it does not enable remote control. The most important options of this configuration file are:

More information about smpppd is available in the smpppd(8) and smpppd.conf(5) man pages.

KInternet, cinternet, and qinternet can be used to control a local or remote smpppd. cinternet is the command-line counterpart of the graphical KInternet. qinternet is basically the same as KInternet, but does not use the KDE libraries, so it can be used without KDE and must be installed separately. To prepare these utilities for use with a remote smpppd, edit the configuration file /etc/smpppd-c.conf manually or using KInternet. This file only uses three options:

If smpppd is active, you can now try to access it, for example, with cinternet --verbose --interface-list. If you experience difficulties at this point, refer to the smpppd-c.conf(5) and cinternet(8) man pages.