1IFTAB(5) Linux Programmer's Manual IFTAB(5)
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6 iftab - static information about the network interfaces
7
9 The file /etc/iftab contains descriptive information about the various
10 network interfaces. iftab is only used by the program ifrename(8) to
11 assign a consistent network interface name to each network interface.
12 /etc/iftab defines a set of mappings. Each mapping contains an inter‐
14 face name and a set of selectors. The selectors allow ifrename to iden‐
15 tify each network interface on the system. If a network interface
16 matches all descriptors of a mapping, ifrename attempt to change the
17 name of the interface to the interface name given by the mapping.
18
20 Each mapping is described on a separate line, it starts with an inter‐
21 face name, and contains a set of descriptors, separated by space or
22 tabs.
23 The relationship between descriptors of a mapping is a logical and. A
25 mapping matches a network interface only is all the descriptors match.
26 If a network interface doesn't support a specific descriptor, it won't
27 match any mappings using this descriptor.
28 If you want to use alternate descriptors for an interface name (logical
30 or), specify two different mappings with the same interface name (one
31 on each line). Ifrename always use the first matching mapping starting
32 from the end of iftab, therefore more restrictive mapping should be
33 specified last.
34
36 The first part of each mapping is an interface name. If a network
37 interface matches all descriptors of a mapping, ifrename attempt to
38 change the name of the interface to the interface name given by the
39 mapping.
40 The interface name of a mapping is either a plain interface name (such
42 as eth2 or wlan1) or a interface name pattern containing a single wild‐
43 card (such as eth* or wlan*). In case of wildcard, the kernel replace
44 the '*' with the lowest available integer making this interface name
45 unique. Note that wildcard is only supported for kernel 2.6.1 and
46 2.4.30 and later.
47 It is discouraged to try to map interfaces to default interfaces names
49 such as eth0, wlan0 or ppp0. The kernel use those as the default name
50 for any new interface, therefore most likely an interface will already
51 use this name and prevent ifrename to use it. Even if you use takeover,
52 the interface may already be up in some cases. Not using those name
53 will allow you to immediately spot unconfigured or new interfaces.
54 Good names are either totally unique and meaningfull, such as mydsl or
55 privatehub, or use larger integer, such as eth5 or wlan5. The second
56 type is usually easier to integrate in various network utilities.
57
59 Each descriptor is composed of a descriptor name and descriptor value.
60 Descriptors specify a static attribute of a network interface, the goal
61 is to uniquely identify each piece of hardware.
62 Most users will only use the mac selector despite its potential prob‐
64 lems, other selectors are for more specialised setup. Most selectors
65 accept a '*' in the selector value for wilcard matching, and most
66 selectors are case insensitive.
67 mac mac address
69 Matches the MAC Address of the interface with the specified MAC
70 address. The MAC address of the interface can be shown using
71 ifconfig(8) or ip(8).
72 This is the most common selector, as most interfaces have a
73 unique MAC address allowing to identify network interfaces with‐
74 out ambiguity. However, some interfaces don't have a valid MAC
75 address until they are brought up, in such case using this
76 selector is tricky or impossible.
77 arp arp type
79 Matches the ARP Type (also called Link Type) of the interface
80 with the specified ARP type as a number. The ARP Type of the
81 interface can be shown using ifconfig(8) or ip(8), the
82 link/ether type correspond to 1 and the link/ieee802.11 type
83 correspond to 801.
84 This selector is useful when a driver create multiple network
85 interfaces for a single network card.
86 driver driver name
88 Matches the Driver Name of the interface with the specified
89 driver name. The Driver Name of the interface can be shown using
90 ethtool -i(8).
91 businfo bus information
93 Matches the Bus Information of the interface with the specified
94 bus information. The Bus Information of the interface can be
95 shown using ethtool -i(8).
96 firmware firmware revision
98 Matches the Firmware Revision of the interface with the firmware
99 revision information. The Firmware Revision of the interface can
100 be shown using ethtool -i(8).
101 baseaddress base address
103 Matches the Base Address of the interface with the specified
104 base address. The Base Address of the interface can be shown
105 using ifconfig(8).
106 Because most cards use dynamic allocation of the Base Address,
107 this selector is only useful for ISA and EISA cards.
108 irq irq line
110 Matches the IRQ Line (interrupt) of the interface with the spec‐
111 ified IRQ line. The IRQ Line of the interface can be shown using
112 ifconfig(8).
113 Because there are IRQ Lines may be shared, this selector is usu‐
114 ally not sufficient to uniquely identify an interface.
115 iwproto wireless protocol
117 Matches the Wireless Protocol of the interface with the speci‐
118 fied wireless protocol. The Wireless Protocol of the interface
119 can be shown using iwconfig(8) or iwgetid(8).
120 This selector is only supported on wireless interfaces and is
121 not sufficient to uniquely identify an interface.
122 pcmciaslot pcmcia slot
124 Matches the Pcmcia Socket number of the interface with the spec‐
125 ified slot number. Pcmcia Socket number of the interface can be
126 shown using cardctl ident(8).
127 This selector is usually only supported on 16 bits cards, for 32
128 bits cards it is advised to use the selector businfo.
129 prevname previous interface name
131 Matches the name of the interface prior to renaming with the
132 specified oldname.
133 This selector should be avoided as the previous interface name
134 may vary depending on various condition. A system/kernel/driver
135 update may change the original name. Then, ifrename or another
136 tool may rename it prior to the execution of this selector.
137 SYSFS{filename} value
139 Matches the content the sysfs attribute given by filename to the
140 specified value. For symlinks and parents directories, match the
141 actual directory name of the sysfs attribute given by filename
142 to the specified value.
143 A list of the most useful sysfs attributes is given in the next
144 section.
145
147 Sysfs attributes for a specific interface are located on most systems
148 in the directory named after that interface at /sys/class/net/. Most
149 sysfs attribute are files, and their values can be read using cat(1) or
150 more(1). It is also possible to match attributes in subdirectories.
151 Some sysfs attributes are symlinks, pointing to another directory in
153 sysfs. If the attribute filename is a symlink the sysfs attribute
154 resolves to the name of the directory pointed by the symlink using
155 readlink(1). The location is a directory in the sysfs tree is also
156 important. If the attribute filename ends with /.., the sysfs attribute
157 resolves to the real name of the parent directory using pwd(1).
158 The sysfs filesystem is only supported with 2.6.X kernel and need to be
160 mounted (usually in /sys). sysfs selectors are not as efficient as
161 other selectors, therefore they should be avoided for maximum perfor‐
162 mance.
163 These are common sysfs attributes and their corresponding ifrename
165 descriptors.
166 SYSFS{address} value
168 Same as the mac descriptor.
169 SYSFS{type} value
171 Same as the arp descriptor.
172 SYSFS{device} value
174 Valid only up to kernel 2.6.20. Same as the businfo descriptor.
175 SYSFS{..} value
177 Valid only from kernel 2.6.21. Same as the businfo descriptor.
178 SYSFS{device/driver} value
180 Valid only up to kernel 2.6.20. Same as the driver descriptor.
181 SYSFS{../driver} value
183 Valid only from kernel 2.6.21. Same as the driver descriptor.
184 SYSFS{device/irq} value
186 Valid only up to kernel 2.6.20. Same as the irq descriptor.
187 SYSFS{../irq} value
189 Valid only from kernel 2.6.21. Same as the irq descriptor.
190
192 # This is a comment
193 eth2 mac 08:00:09:DE:82:0E
194 eth3 driver wavelan interrupt 15 baseaddress 0x390
195 eth4 driver pcnet32 businfo 0000:02:05.0
196 air* mac 00:07:0E:* arp 1
197 myvpn SYSFS{address} 00:10:83:* SYSFS{type} 1
198 bcm* SYSFS{device} 0000:03:00.0 SYSFS{device/driver} bcm43xx
199 bcm* SYSFS{..} 0000:03:00.0 SYSFS{../driver} bcm43xx
200
202 Jean Tourrilhes - jt@hpl.hp.com
203
205 /etc/iftab
206
208 ifrename(8), ifconfig(8), ip(8), ethtool(8), iwconfig(8).
209wireless-tools 26 February 2007 IFTAB(5)