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Chapter 6: Port Trunking
84 Section I: Using the Menus Interface
LACP Trunks
An LACP (Link Aggregation Control Protocol) trunk is another type of port
trunk. It performs the same function as a static trunk. It increases the
bandwidth between two network devices by distributing the traffic load
over multiple physical links.
The advantage of an LACP trunk over a static port trunk is its flexibility.
While implementations of static trunking tend to be vendor specific, the
AT-S84 implementation of LACP is compliant with the IEEE 802.3ad
standard. This makes it interoperable with equipment from other vendors
that also comply with the standard. Therefore, you can create a trunk
between an Allied Telesis device and networking devices from other
manufacturers.
Another advantage is that ports in an LACP trunk can function in a
standby mode. This adds redundancy and resiliency to the trunk. If a link
in a static trunk goes down, the overall bandwidth of the trunk is reduced
and restoring it requires reestablishing the link or manually modifying the
trunk by adding another port to it. In contrast, an LACP trunk can activate
ports in a standby mode when an active link fails. The automatic activation
of standby ports allows the switch to maintain the maximum possible
bandwidth of the trunk.
For example, assume you create an LACP trunk of ports 11 to 18 on a
switch and the switch is using ports 11 to 16 as the active ports and ports
17 and 18 as reserve. If an active port loses its link, the switch
automatically activates one of the two reserve ports to maintain maximum
bandwidth of the trunk. Figure 20 illustrates this example.
Figure 20. LACP Trunk Example
LACP Trunk
Status
The AT-9000/24 Gigabit Ethernet switch can have up to four trunks. A
maximum of eight ports of each trunk can be assigned by the switch
administrator. You can configure each trunk’s status as Active, Passive,
Manual, or Disabled.
793
AT-9000/24
24 Port Gigabit Ethernet Switch
1
3
57
9111315
17 1921R
23R
2 4 6 8 1012 14 1618 2022R24R
POWER
21 22
23 24
SFP
LINK ACT
1000
10/100
PORT ACTIVITY
793
AT-9000/24
24 Port Gigabit Ethernet Switch
1
3
57
9111315
17 1921R
23R
2 4 6 8 1012 14 1618 2022R24R
POWER
21 22
23 24
SFP
LINK ACT
1000
10/100
PORT ACTIVITY
Active Ports 11-16
Reserve Ports 17, 18