Thank you for all your advices, I am sorry for that I may not have
time and chance to try bridge mode on NetBSD-current.

The bridge mode package is at pkgsrc/net/bridged.
It might be current choice for me under -stable :)

Emre Yildirim wrote:

> Gavan Fantom wrote:
>
>> On Wed, 14 Nov 2001, Chun-Ying Huang wrote:
>>
>>> Does NetBSD (1.5.2) support in-kernel bridge mode?
>>
>> No, although I believe -current does.
>
> I think Jason Thorpe was working on it the last time I checked. From
> netbsd.org's news section:
> Bridge support added to NetBSD-current (17 Aug) (top)
> Jason Thorpe has committed support for building Ethernet bridges to
> NetBSD-current. Bridges are configured with a combination of
> ifconfig(8) and the new brconfig(8) utility. brconfig(8) can also be
> used to show a bridge's status, like so:
> swinger:thorpej 1$ brconfig -a
> bridge0: flags=41<UP,RUNNING>
> Configuration:
> priority 32768 hellotime 2 fwddelay 15 maxage 20
> Interfaces:
> fxp2 flags=3<LEARNING,DISCOVER>
> port 4 priority 128
> tlp0 flags=3<LEARNING,DISCOVER>
> port 5 priority 128
> Address cache (max cache: 100, timeout: 1200):
> 00:20:6f:04:13:1d tlp0 1169 flags=0<>
> 08:00:2b:2b:a9:0e tlp0 914 flags=0<>
> 00:03:47:20:1b:7d fxp2 191 flags=0<>
> 00:00:f8:23:43:9d tlp0 148 flags=0<>
> swinger:thorpej 2$
> If you use the bridge code, please send Jason a mail and report on how
> well it works for you. If you have problems with it, please file a bug
> report with send-pr(1).
> This support is based off Jason Wright's bridge driver for OpenBSD,
> with changes by Jason Thorpe.

-- 
Regards,
huangant <Chun-Ying Huang>