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AGR(4) NetBSD Kernel Interfaces Manual AGR(4)
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agr -- link aggregation pseudo network interface driver
The agr driver provides link aggregation functionality (a.k.a. L2 trunk-
ing or bonding).
It supports the IEEE 802.3ad Link Aggregation Control Protocol (LACP) and
the Marker Protocol.
The agr driver supports the following link specific flags for
link0 Use the round-robin distribution algorithm. Don't use it unless
you're really sure, because it violates the frame ordering rule.
-link0 Use the default distribution algorithm, which is based on the
hash of DA/SA, TCI, and, if available, some upper layer protocol
information like ip(4) DA/SA.
link1 Disable LACP. Prevents any LACP or Marker messaging which leaves
the ports in the default static configuration. Set this prior to
Create an agr interface, agr0, and attach re0 and re1 to it. In other
words, aggregate re0 and re1 so that they can be used as a single inter-
face, agr0. The physical interfaces which are attached to the agr inter-
face must not have any IP addresses, neither IPv4 nor IPv6.
ifconfig re0 inet xxx.xxx.xxx.xxx delete
ifconfig re0 inet6 fe80::xxxx:xxxx:xxxx:xxxx delete
ifconfig re1 inet xxx.xxx.xxx.xxx delete
ifconfig re1 inet6 fe80::xxxx:xxxx:xxxx:xxxx delete
ifconfig agr0 create
ifconfig agr0 agrport re0
ifconfig agr0 agrport re1
Destroy an interface created in the above example.
ifconfig agr0 -agrport re0
ifconfig agr0 -agrport re1
ifconfig agr0 destroy
IEEE 802.3ad Aggregation of Multiple Link Segments
The agr driver first appeared in NetBSD 4.0.
The agr driver was written by YAMAMOTO Takashi.
There is no way to configure LACP administrative variables, including
system and port priorities. The current implementation of the agr driver
always performs active-mode LACP and uses 0x8000 as system and port pri-
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
The current implementation of the agr driver doesn't prevent unsafe oper-
ations like some ioctls against underlying physical interfaces. Such
operations can result in unexpected behaviors, and are strongly discour-
There is no way to configure agr interfaces without attaching physical
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. Note that it includes an automatically assigned IPv6
NetBSD 9.0 February 23, 2010 NetBSD 9.0