vlan - IEEE 802.1Q VLAN network interface
device miibus device vlan
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf5:
Each interface is created at runtime using interface cloning. This is most easily done with the ifconfig(8) create command or using the cloned_interfaces variable in rc.conf5.
To function, a interface must be assigned a parent interface and numeric VLAN tag using ifconfig(8). A single parent can be assigned to multiple interfaces provided they have different tags. The parent interface is likely to be an Ethernet card connected to a properly configured switch port. The VLAN tag should match one of those set up in the switched network.
Initially assumes the same minimum length for tagged and untagged frames. This mode is selected by the sysctl(8) variable net.link.vlan.soft_pad set to 0 (default). However, there are network devices that fail to adjust frame length, should it fall below the allowed minimum due to untagging. Such devices should be able to interoperate with after changing the value of net.link.vlan.soft_pad to 1. In the latter mode, will pad short frames before tagging them so that their length stays not less than the minimum value after untagging by the non-compliant devices.
By now, the list of physical interfaces able of full VLAN processing in the hardware is limited to the following devices: ae(4), age(4), ale(4), bce(4), bge(4), cxgb(4), em(4), ixgb(4), jme(4), msk(4), nge(4), re(4), stge(4), ti(4), txp(4), and vge(4).
The rest of the Ethernet interfaces can run VLANs using software emulation in the driver. However, some of them lack the capability of transmitting and receiving long frames. Assigning such an interface as the parent to will result in a reduced MTU on the corresponding interfaces. In the modern Internet, this is likely to cause tcp(4) connectivity problems due to massive, inadequate icmp(4) filtering that breaks the Path MTU Discovery mechanism.
The following interfaces support long frames for natively: bfe(4), dc(4), fwe(4), fxp(4), gem(4), hme(4), le(4), nfe(4), nve(4), rl(4), sf(4), sis(4), sk(4), ste(4), tl(4), tx(4), vr(4), and xl(4).
The driver automatically recognizes devices that natively support long frames for use and calculates the appropriate frame MTU based on the capabilities of the parent interface. Some other interfaces not listed above may handle long frames, but they do not advertise this ability of theirs. The MTU setting on can be corrected manually if used in conjunction with such a parent interface.
EVFILT_NETDEV events on a interface will be sent through kqueue(2) only if the parent interface uses miibus(4) for link state notification.
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Created 1996-2023 by Maxim Chirkov
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