A: Link Aggregation (some vendors refer to this as connection
bonding) is simple to configure. NetBSD includes the agr driver which
supports the IEEE 802.3ad Link Aggregation Control Protocol.

To start, you will need to compile a kernel with the agr driver. Your
kernel config should include.

  pseudo-device         agr

 
With the driver compiled into the kernel, you setup the interface much like
as you would any other. The following is an example /etc/ifconfig.agr0

  create
  agrport sip0
  agrport sip1
  inet 10.0.0.50 netmask 0xffffff00

 
A few notes taken verbatim from the man page.

  The agr driver uses the MAC address of the first-added physical interface
  as the MAC address of the agr interface itself.  Thus, removing the phys-
  ical interface and using it for another purpose can result in non-unique
  MAC addresses.

  Physical interfaces being added to the agr interface shouldn't have any
  addresses except for link level address.  Otherwise, the attempt will
  fail with EBUSY.