Bridging Gigabit and Fast Ethernet Interfaces

Carl Chave carl at
Mon Nov 29 04:52:08 UTC 2010

if_bridge(4) says:

The if_bridge driver currently supports only Ethernet and Ethernet-like
(e.g., 802.11) network devices, with exactly the same interface MTU size
as the bridge device.

Am I correct to assume then that I can bridge a gigabit interface and
a fast ethernet interface and that one of the "negatives" of doing
this is that Jumbo frames couldn't be used on the gigabit side?  I've
got an Atom based server with an onboard gigabit nic and only one PCI
slot.  The server sits physically close to my 10/100 switch that hangs
off my firewall.  I was thinking of putting a 10/100 nic into the
single PCI slot and running that to the 10/100 switch for internet
access and then running cable across the room from the gigabit
interface to a gigabit switch on my workbench.  Wired gigabit clients
on the bench would then have the benefit of gigabit access to the
server for doing backups but also still have internet access via the
server's bridge interface right?

Is there a reason I wouldn't want to do it this way?



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