| 10.0.x.x | 16,777,216 | One Class A network of 16,777,216 addresses |
| 172.16.x.x172.31.x.x | 1,048,576 | 16 class B networks of 65,536 addresses each |
| 192.168.x.x | 65,536 | 256 class C networks of 256 addresses each |
The Linux kernel keeps track of network devices in the form of interfaces . Each interface is assigned a unique name, such as eth0 , etH1 , eth2 , tr0 , tr1 , tr2 , and so forth. The interface name is initially assigned by the device driver and kernel but may be overridden using ifrename . Each interface has a number of flags, statistics, and configuration settings; these values are exposed through /proc/net and /sys/class/net , and are displayed and manipulated by ifconfig . Interface aliases such as eth0:1 and eth0:2 permit multiple interfaces to be assigned to one physical network device.
Packet routing is also performed by the kernel; the kernel routing table is exposed through /proc/net/route and /proc/net/ipv6_route , and is displayed and manipulated by the route command ( netstat -r displays the same information).
The DNS information stored in /etc/ resolv.conf is used by the resolver libraries loaded by applications. Since most resolvers load the contents of /etc/resolv.conf only when an application is started, it is usually necessary to restart your applications after changing the resolver configuration.
As an exception to the rule, Firefox does not need to be restarted after /etc/resolv.conf is changed.
The system-config-network tool is a Python script that manipulates the file /etc/sysconfig/network and the contents of the directory /etc/sysconfig/network-scripts (in addition to the /etc/hosts and /etc/resolv.conf files). These files are then read by the system init script to configure the boot-time network environment, and they are also used by other utilities such as ifup , ifdown , and system-control-network .
The NetworkManager service consists of a single binary, /usr/sbin/NetworkManager, which attempts to keep a network running at all times. The NetworkManagerDispatcher service can be used to launch scripts in /etc/NetworkManager/dispatcher.d as interfaces are brought up and down, but this capability is not used by Fedora Core, so you can leave this service disabled. The GUI component of NetworkManager is provided by nm-applet ( /usr/bin/nm- applet ); the two components communicate through the desktop bus (dbus) mechanism.
Wireless interface drivers provide an extended set of control and monitoring functions called the wireless extensions . There are many versions of the wireless extensions in use, and not all of the extensions are supported by each driver. The current version of the wireless extensions is version 20, and it is expected that this version will remain stable for some time. When a wireless card can be configured by the GUI or command line but not by NetworkManger, it's usually due to incomplete or out-of-date wireless extension support in the interface device.
3.2.3.1. ...using a Fedora system as a router?
A router passes packets from one interface to another, and Fedora is capable of doing this. /proc/sys/net/ipv4/ip_forward controls packet forwarding; writing a 1 to this path enables forwarding:
# echo 1 >/proc/sys/net/ipv4/ip_forward
Likewise, writing a 0 disables forwarding:
# echo 0 >/proc/sys/net/ipv4/ip_forward
3.2.3.2. ...renaming a network interface, or configuring a 'wlan' interface using the GUI configuration tool?
The ifrename utility can be used to rename a network interface. The -i option specifies the old interface name, and -n sets the new name. To rename wlan0 to eth1 , for example:
# ifrename -i wlan0 -n eth1
eth1
# ifconfig wlan0
wlan0: error fetching interface information: Device not found
# ifconfig eth1
eth1 Link encap:Ethernet HWaddr 00:0C:2D:00:2B:DB
BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:0 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:0 (0.0 b) TX bytes:0 (0.0 b)
The GUI network configuration program ( system-config-network ) will
