|LAGG(4)||Device Drivers Manual||LAGG(4)|
lagg — link
aggregation and link failover interface
To compile this driver into the kernel, place the following line in your kernel configuration file:
Alternatively, to load the driver as a module at boot time, place the following line in loader.conf(5):
lagg interface allows aggregation of
multiple network interfaces as one virtual
interface for the purpose of providing fault-tolerance and high-speed
lagg interface can be created using the
create command. It can use different link
aggregation protocols specified using the
proto option. Child interfaces can be added using the
laggport child-iface option
and removed using the
The driver currently supports the aggregation protocols
failover (the default),
none. The protocols determine which ports are used
for outgoing traffic and whether a specific port accepts incoming traffic.
The interface link state is used to validate if the port is active or
- Sends traffic only through the active port. If the master port becomes
unavailable, the next active port is used. The first interface added is
the master port; any interfaces added after that are used as failover
By default, received traffic is only accepted when they are received through the active port. This constraint can be relaxed by setting the net.link.lagg.failover_rx_all sysctl(8) variable to a nonzero value, which is useful for certain bridged network setups.
- Supports the IEEE 802.1AX (formerly 802.3ad) Link Aggregation Control Protocol (LACP) and the Marker Protocol. LACP will negotiate a set of aggregable links with the peer in to one or more Link Aggregated Groups. Each LAG is composed of ports of the same speed, set to full-duplex operation. The traffic will be balanced across the ports in the LAG with the greatest total speed, in most cases there will only be one LAG which contains all ports. In the event of changes in physical connectivity, Link Aggregation will quickly converge to a new configuration.
- Balances outgoing traffic across the active ports based on hashed protocol header information and accepts incoming traffic from any active port. This is a static setup and does not negotiate aggregation with the peer or exchange frames to monitor the link. The hash includes the Ethernet source and destination address, and, if available, the VLAN tag, and the IP source and destination address.
- Distributes outgoing traffic using a round-robin scheduler through all
active ports and accepts incoming traffic from any active port. Using
roundrobinmode can cause unordered packet arrival at the client. Throughput might be limited as the client performs CPU-intensive packet reordering.
- Sends frames to all ports of the LAG and receives frames on any port of the LAG.
- This protocol is intended to do nothing: it disables any traffic without
lagg interface is created at runtime
using interface cloning. This is most easily done with the
create command or
using the cloned_interfaces variable in
The MTU of the first interface to be added is used as the lagg MTU. All additional interfaces are required to have exactly the same value.
lacp modes will use the RSS hash from the network
card if available to avoid computing one, this may give poor traffic
distribution if the hash is invalid or uses less of the protocol header
information. Local hash computation can be forced per interface by setting
use_flowid ifconfig(8) flag.
The default for new interfaces is set via the
Create a link aggregation using LACP with two bge(4) Gigabit Ethernet interfaces:
# ifconfig bge0 up # ifconfig bge1 up # ifconfig lagg0 create # ifconfig lagg0 laggproto lacp laggport bge0 laggport bge1 \ 192.168.1.1 netmask 255.255.255.0
Create a link aggregation using ROUNDROBIN with two bge(4) Gigabit Ethernet interfaces and set the limit of 500 packets per interface:
# ifconfig bge0 up # ifconfig bge1 up # ifconfig lagg0 create # ifconfig lagg0 laggproto roundrobin laggport bge0 laggport bge1 \ 192.168.1.1 netmask 255.255.255.0 # ifconfig lagg0 rr_limit 500
The following example uses an active failover interface to set up roaming between wired and wireless networks using two network devices. Whenever the wired master interface is unplugged, the wireless failover device will be used:
# ifconfig em0 up # ifconfig ath0 ether 00:11:22:33:44:55 # ifconfig create wlan0 wlandev ath0 ssid my_net up # ifconfig lagg0 create # ifconfig lagg0 laggproto failover laggport em0 laggport wlan0 \ 192.168.1.1 netmask 255.255.255.0
(Note the mac address of the wireless device is forced to match the wired device as a workaround.)
lagg device first appeared in
lagg driver was written under the name
trunk by Reyk Floeter
The LACP implementation was written by YAMAMOTO
Takashi for NetBSD.
There is no way to configure LACP administrative variables, including system and port priorities. The current implementation always performs active-mode LACP and uses 0x8000 as system and port priorities.
|January 23, 2016||Debian|