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33 .Nd "IEEE 802.1Q VLAN network interface"
35 To compile this driver into the kernel,
36 place the following lines in your
37 kernel configuration file:
38 .Bd -ragged -offset indent
43 Alternatively, to load the driver as a
44 module at boot time, place the following line in
46 .Bd -literal -offset indent
52 driver demultiplexes frames tagged according to
53 the IEEE 802.1Q standard into logical
55 network interfaces, which allows routing/bridging between
56 multiple VLANs through a single switch trunk port.
60 interface is created at runtime using interface cloning.
62 most easily done with the
72 interface must be assigned a parent interface and
73 numeric VLAN tag using
75 A single parent can be assigned to multiple
77 interfaces provided they have different tags.
78 The parent interface is likely to be an Ethernet card connected
79 to a properly configured switch port.
80 The VLAN tag should match one of those set up in the switched
85 driver supports efficient operation over parent interfaces that can provide
86 help in processing VLANs.
87 Such interfaces are automatically recognized by their capabilities.
88 Depending on the level of sophistication found in a physical
89 interface, it may do full VLAN processing or just be able to
90 receive and transmit frames exceeding the maximum Ethernet frame size
91 by the length of a 802.1Q header.
92 The capabilities may be user-controlled by the respective parameters to
97 However, a physical interface is not obliged to react to them:
98 It may have either capability enabled permanently without
100 The whole issue is very specific to a particular device and its driver.
102 By now, the list of physical interfaces able of full VLAN processing
103 in the hardware is limited to the following devices:
114 The rest of the Ethernet interfaces can run
115 VLANs using software emulation in the
118 However, most of them lack the capability
119 of transmitting and receiving oversized frames.
120 Assigning such an interface as the parent to
122 will result in a reduced MTU on the corresponding
125 In the modern Internet, this is likely to cause
127 connectivity problems due to massive, inadequate
129 filtering that breaks the Path MTU Discovery mechanism.
131 The interfaces that support oversized frames are as follows:
132 .Bl -tag -width ".Xr fxp 4 " -offset indent
134 supports long frames for
138 supports long frames for
145 .Pa /usr/src/sys/pci/if_de.c
146 source file and rebuilding the kernel
148 The hack works only for the 21041, 21140, and 21140A chips.
150 supports long frames for
154 supports long frames for
158 supports long frames for
162 supports long frames for
166 supports long frames for
170 supports long frames for
174 supports long frames for
178 has support for long frames.
180 supports long frames for
184 supports long frames only if the card is built on a newer chip
190 driver automatically recognizes devices that natively support oversized frames
193 use and calculates the appropriate frame MTU based on the
194 capabilities of the parent interface.
195 The other interfaces listed above can handle oversized frames,
196 but they do not advertise this ability of theirs.
199 can be corrected manually if used in conjunction with such parent interface.
205 No 802.1Q features except VLAN tagging are implemented.
210 interface will be sent through
212 only if the parent interface uses
214 for link state notification.