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D-Link DGS-3212SR Layer 2 Gigabit Ethernet Switch
Section 7
Link Aggregation Configuration
Link aggregation allows several ports to be grouped together and to act as a single link. This gives a bandwidth
that is a multiple of a single link’s bandwidth.
Link aggregation is most commonly used to link a bandwidth intensive network device or devices, such as a
server, to the backbone of a network.
The switch allows the creation of up to 6 link aggregation groups, each group consisting of up of up to 8 links
(ports). The aggregated links must be contiguous (they must have sequential port numbers) except the two
(optional) Gigabit ports, which can only belong to a single link aggregation group. A link aggregation group may
not cross an 8-port boundary, starting with port 1 (a group may not contain ports 8 and 9, for example) and all of
the ports in the group must be members of the same VLAN. Further, the aggregated links must all be of the
same speed and should be configured as full-duplex.
The configuration of the lowest numbered port in the group becomes the configuration for all of the ports in the
aggregation group. This port is called the Master Port of the group, and all configuration options, including the
VLAN configuration, that can be applied to the Master Port are applied to the entire link aggregation group.
Load balancing is automatically applied to the ports in the aggregated group, and a link failure within the group
causes the network traffic to be directed to the remaining links in the group.
The Spanning Tree Protocol will treat a link aggregation group as a single link, on the switch level. On the port
level, the STP will use the port parameters of the Master Port in the calculation of port cost and in determining
the state of the link aggregation group. If two redundant link aggregation groups are configured on the switch,
STP will block one entire group, in the same way STP will block a single port that has a redundant link.
To configure port trunking, click on the Link Aggregation hyperlink in the Configuration folder to bring up the
Port Trunk Group Entries table:
Figure 7-1. Port Trunking Group Entry Table
To configure port trunk groups, click the Add button to add a new trunk group and use the menu Port Trunking
Group menu (see example below) to set up trunk groups. To change or delete a port trunk group, click the
Modify or Delete option in the Port Trunk Group Entries table.
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