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What are link aggregation and LACP and how can I use them in my network?

2019/09 7
Z-CUG01 Dual-Port PCI-E Gigabit Ethernet Network Card - IEEE 802.3ad (Link Aggregation) Supported

Link aggregation allows you to combine multiple Ethernet links into a single logical link between two networked devices.

• Link aggregation is sometimes called by other names:
• Ethernet bonding
• Ethernet teaming
• Link bonding
• Link bundling
• Link teaming
• Network interface controller (NIC) bonding
• NIC teaming
• Port aggregation
• Port channeling
• Port trunking

The most common device combinations involve connecting a switch to another switch, a server, a network attached storage (NAS) device, or a multi-port access point. Network devices and management functions treat the link aggregation group (LAG) of multiple Ethernet connections as a single link. For example, you can include a LAG in a virtual local area network (VLAN). You can also configure more than one LAG on the same switch, or add more than two Ethernet links to the same LAG (the maximum number of links per LAG depends on your device). Some network devices support Link Aggregation Control Protocol (LACP), which helps to prevent errors in the link aggregation setup process.

Note: Unmanaged switches do not support link aggregation.


■ What are the benefits of link aggregation?

• Increased reliability and availability - If one of the physical links in the LAG goes down, traffic is dynamically and transparently reassigned to one of the other physical links.
• Better use of physical resources - Traffic can be load-balanced across the physical links.
• Increased bandwidth - The aggregated physical links deliver higher bandwidth than each individual link.
• Cost effectiveness - A physical network upgrade can be expensive, especially if it requires new cable runs. Link aggregation increases bandwidth without requiring new equipment.

■ What are the different types of LAGs?
The two primary types of LAGs are static (also known as manual) and dynamic. Dynamic LAGs use Link Aggregation Control Protocol (LACP) to negotiate settings between the two connected devices. Some devices support static LAGs, but do not support dynamic LAGs with LACP. Refer to your product’s user manual to see whether your device supports LACP. Linux-based devices, such as NETGEAR ReadyNAS storage devices, often offer several additional types of link aggregation that provide increased fault tolerance or load balancing instead of increased bandwidth.

■ What is Link Aggregation Control Protocol (LACP)?
Link Aggregation Control Protocol is an IEEE standard defined in IEEE 802.3ad. LACP lets devices send Link Aggregation Control Protocol Data Units (LACPDUs) to each other to establish a link aggregation connection. You still need to configure the LAG on each device, but LACP helps prevent one of the most common problems that can occur during the process of setting up link aggregation: misconfigured LAG settings. If the devices detect that they cannot establish a link aggregation connection, they do not try to establish it, and the link shows as “down” in the admin interface.

Another useful feature of LACP is that when one member link stops sending LACPDUs (if the cable is unplugged, for example), it is removed from the LAG. This helps to minimize packet loss. Both devices must support LACP for you to set up a dynamic LAG between those devices. We recommend using LACP instead of a static LAG whenever both devices support LACP.

■ How do I set up link aggregation in my network?
The following instructions describe in general terms how to set up link aggregation between two devices in your network. For more information about setting up link aggregation on specific NETGEAR devices, see the NETGEAR product support page for your product. To find your product’s support page, visit https://www.netgear.com/support/ and enter your product model number in the search box.

To set up link aggregation between two devices in your network:
1. Make sure that both devices support link aggregation.
2. Configure the LAG on each of the two devices.
3. Make sure that the LAG that you create on each device has the same settings for port speed, duplex mode, flow control, and MTU size (on some devices, this setting might be called jumbo frames).
4. Make sure that all ports that are members of a LAG have the same virtual local area network (VLAN) memberships. If you want to add a LAG to a VLAN, set up the LAG first and then add the LAG to the VLAN; do not add individual ports.

Warning!!!
Do not connect the devices to each other using more than one Ethernet cable until after you set up the LAG on each device. If you form multiple connections between the two devices and neither device has loop prevention, you create a network loop. Network loops can slow or stop normal traffic on your network.

5. Note which ports on each device you add to the LAG, and make sure that you connect the correct ones. The LAG issues an alert and rejects the configuration if port members have different settings for port speed, duplex mode, or MTU size, or if you accidentally connect ports that are not members of the LAG.
6. Use Ethernet or fiber cable to connect the ports that you added to the LAG on each device.
7. Verify that the port LED for each connected port on each NETGEAR switch is blinking green.
8. Verify in the admin interface for each device that the link is UP.

TAG: Z-CUG01 CU201