надеюсь по англ все поймут
для FreeBSD 5.3
Selecting the Right Network Interface Card to Run VLANs Through
By now, the only NICs that have both hardware support and proper driver
hooks for the 802.1Q VLAN technology in FreeBSD are bge(4), em(4), gx(4),
nge(4), re(4), ti(4), and txp(4).
The rest of the ethernet NICs supported by FreeBSD can run VLANs using
software emulation in the vlan driver. However, most of them lack the
capability of transmitting and/or receiving oversized frames. Using such
a NIC as a parent interface implies a reduced MTU on the corresponding
vlan 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 NICs that support oversized frames are as follows:
bfe(4) supports long frames for vlan natively.
dc(4) supports long frames for vlan natively.
de(4) requires defining BIG_PACKET in the
/usr/src/sys/pci/if_de.c source file and rebuilding the
kernel or module. The hack works only for the 21041,
21140, and 21140A chips.
fxp(4) supports long frames for vlan natively.
hme(4) supports long frames for vlan natively.
rl(4) supports long frames for vlan natively.
sis(4) supports long frames for vlan natively.
ste(4) supports long frames for vlan natively.
tl(4) has support for long frames.
tx(4) supports long frames for vlan natively.
xl(4) supports long frames only if the card is built on a newer
chip (Cyclone and above).
The vlan driver automatically recognizes devices that support oversized
frames for vlan use and calculates the appropriate frame MTU based on the
capabilities of the parent interface.