VI. Feature Setup

Link Aggregation between VigorSwitch switches (Trunking)

Products:
VigorSwitch G1080
VigorSwitch G1085
VigorSwitch G1280
VigorSwitch G2100
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Keywords:
Bonding
LACP
LAG
Link Aggregation
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Load Balancing, Redundancy and increased bandwidth with Link Aggregation

DrayTek VigorSwitches support Link Aggregation Control Protocol (LACP), the IEEE 802.3ad standard, which is a method to recognise that two or more links connect to another network switch or server, without causing a network loop to occur and instead using the multiple links constructively.

This is also called Trunking.

LACP makes it possible to connect two or more network links between switches and servers, allowing for higher combined throughput, load balancing and redundancy.

Link Aggregation combines several physical ports into one logical port with a greater total bandwidth (an aggregate of each port's bandwidth in the Link Aggregation Group (LAG)), with two 1Gbps links giving an aggregated total bandwidth of 2Gbps, improving transfer speeds for multiple users across the network and avoiding switch-to-switch connections becoming a bottleneck.

Link Aggregation load balances traffic between multiple ports, but is not bonding those links, so the total bandwidth for a single session is still limited by the data rate of a single port i.e. 1Gbps, but multiple sessions can make full use of the additional bandwidth. This load balancing also provides redundant connectivity - should one of the cables become disconnected, the link between the two switches remains active on the remaining port(s).

Setup Example

Link Aggregation between VigorSwitch P1280 and VigorSwitch P2280

This guide will demonstrate how to connect a VigorSwitch P1280 and VigorSwitch P2280 together using LACP to load balance two to four 1Gbps network links. The following setup can be used to potentially connect up to eight links between the two switches.

Each of the VigorSwitches is linked to the Vigor 2862 for configuration and IP addressing via DHCP. In its initial state, the two switches are connected directly to the router, with no link between the two VigorSwitches. This is to avoid network loops and broadcast storms, which can break network connectivity when they occur.

The multiple network cables that will be utilised by the Link Aggregation Group will not be connected until after both switches have been configured correctly.

With the two switches connected to the router, connect your computer to a LAN port on the DrayTek router. Access the Web Interface of each switch, configuring each switch with these settings.

Important Note - Link Aggregation Group Port Cables
Do not connect the cables between the two switches until instructed. As you can see in the image above, the two switches are not linked - yet !

Locating the VigorSwitch web configuration IP address

To find out the IP addresses of each switch, either use the DrayTek Device Finder utility, or locate the switches with the router.

To locate the switches from the router, access the router's web interface and check the router's Switch Management status accessing:
[Central Management] > [Switch] > [Status]
The VigorSwitch IP addresses will be listed in the Switch Status tab.

On older DrayTek routers that do not support Switch Management, check the [External Devices] menu.

Load Balance Mode - LAG Setting

In the web interface of the VigorSwitch, go to [Switch LAN] > [Link Aggregation] > [LAG Setting] and select the Load Balance Algorithm, which affects how traffic is balanced by the link aggregation system.

This can operate in one of two modes:

  • "MAC Address" (OSI layer 2) which balances traffic for different MAC addresses
  • "IP & MAC Address" (OSI layers 3 & 2), which balances traffic both for different IP addresses (or by MAC address for non TCP/IP packets).

We recommend to use "IP & MAC Address" as the load balancing method, because this allows Router, Internet & VPN traffic to be considered when assigning a link to a new session.

Click Apply to save and apply that change.

Link Aggregation Control Protocol - LACP Settings

In the web interface of the VigorSwitch, go to [Switch LAN] > [Link Aggregation] > [LACP Setting].

Ensure that the LACP setting is enabled. The System Priority can be left with its default value, but if one of the switches is intended to operate as a 'main' switch, reduce the value from its default 32768 to a smaller number, such as 32767, which increases its priority for LACP control. The switch with the highest priority will actively control the ports in the link.

Click Apply to save and apply any changes.

Link Aggregation Group - LAG Management

In the web interface of the VigorSwitch, go to [Switch LAN] > [Link Aggregation] > [LAG Management]. This lists the available Link Aggregation profiles on the VigorSwitch - when configured, this will show the active status of the Link Aggregation Group.

The LAG numbers (LAG1, LAG2 etc) shown indicate which profile to configure on each VigorSwitch, the LAG group numbers do not need to match between switches for Link Aggregation to work.

Configure LAG1 by clicking Modify, which will pop-up a configuration window for the LAG:

In the pop-up window, configure these settings:

Name Give the group an indicative Name / Description.
Type Select LACP. "LACP" mode is aware of which links are operating correctly and intelligently negotiates which links can be used for the Link Aggregation Group. Wherever possible, link aggregation should use "LACP", with "Static" mode only used for legacy equipment.
Ports Click on the drop-down arrow and select which ports will be assigned to the Link Aggregation Group. This example uses ports 25, 26, 27 and 28

Click OK to save and apply that LAG profile.

VLAN Configuration for Link Aggregation

If your VigorSwitch has VLANs configured, ensure that the Link Aggregation group's VLAN configuration is correct before it is used.

This is configured in the VigorSwitch from the [Switch LAN] > [VLAN Management] > [Interface Settings]. To configure the VLAN settings for the Link Aggregation Group, select the LAG port from the list and configure the required VLAN settings for your network.

Click Apply to save and apply any changes.

The DrayTek VigorSwitch Px280 & Gx280 switches save configuration changes to the switch's start configuration when saving settings.

On older VigorSwitch models such as the VigorSwitch P2261, make sure to save these changes to the VigorSwitch's "start config" once you're sure the settings are correct and working. On the VigorSwitch P2261, this is located in [Maintenance] > [Save/Restore] > [Save Start].

Connecting up the Link Aggregation Group's Network Cables

Once both switches are configured with matching Link Aggregation Groups, LAG1 in this example, the network cables can be connected up.

To do this, first remove the network cable that connects the VigorSwitch P2280 from the DrayTek Vigor 2862 router; this avoids a network loop occurring.

In your setup, ensure that there are no additional links between the VigorSwitches and the router - the Link Aggregation Group will link one VigorSwitch to the other, but connecting a cable from each VigorSwitch to the router, with the LAG in place will result in a loop.

Connect up each of the network cables to the ports in the Link Aggregation Group, in this setup example the ports used are 25, 26, 27 and 28:

Important Note - Check Port Activity Lights
When 2 or more cables are connected, look at the Activity LEDs on the LAN ports of the VigorSwitches and the router - if these all start blinking rapidly and in unison, the Link Aggregation Group is mis-configured and a broadcast storm is occurring.

If the above happens, then immediately disconnect the network cables to the LAG ports and check your switch configuration.
Ensure that the additional links between the VigorSwitches and router do not cause a loop with the LAG port cables connected.

Link Aggregation Status - LAG Management

Once the LAG is set up and the LAG port's cables are connected, the status can be viewed from [Switch LAN] > [Link Aggregation] > [LAG Management].

This will show the active state of the LAG ports, with connected ports displayed in the Active Member column. Ports that are disconnected are listed in the Standby Member column.

If this displays the LAG's Link Status as Up, the Link Aggregation between the two switches is active and traffic between them is load balanced between the ports connecting the two of them.


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