D-Link xStack DES-3800 Series User Manual page 95

The Switch treats all ports in a trunk group as a single port. Data transmitted to a specific host
(destination address) will always be transmitted over the same port in a trunk group. This allows
packets in a data stream to arrive in the same order they were sent.
NOTE: If any ports within the trunk group become disconnected, packets
intended for the disconnected port will be load shared among the other
unlinked ports of the link aggregation group.
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 32 link aggregation groups, each group consisting of 2 to 8
links (ports). The aggregated links must be contiguous (they must have sequential port numbers)
except the four (optional) Gigabit ports, which can only belong to a single link aggregation group. All
of the ports in the group must be members of the same VLAN, and their STP status, static multicast,
traffic control; traffic segmentation and 802.1p default priority configurations must be identical. Port
locking, port mirroring and 802.1X must not be enabled on the trunk group. Further, the aggregated
links must all be of the same speed and should be configured as full duplex.
The Master Port of the group is to be configured by the user, 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
xStack DES-3800 Series Layer 3 Stackable Fast Ethernet Managed Switch
Figure 7- 9. Example of Port Trunk Group
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