Appendix J: Server-To-Switch Distributed Trunking - HP ProCurve 3500-24 Reference Manual

Appendix J: Server-to-Switch Distributed Trunking

Distributed Trunking is a link aggregation technique where two or more links across two switches are
aggregated together to form a trunk . This feature overcomes the limitation in IEEE 802 .3ad that specifies all
links of a trunk have to be from a single switch . Distributed Trunking improves resiliency and load balancing in
a Layer 2 network .
Distributed Trunking (DT) is included in switch software starting with version K . 1 4 . In this initial release, only
Server-to-Switch Distributed Trunking is supported . For each downstream server, it sees the aggregated links as
coming from a single switch, which makes any servers that support standard IEEE 802 .3ad interoperate with
Distributed Trunking .
Distributed trunks can be grouped together by configuring two individual DT-LACP trunks with the common
trunk group name . DT ports will be aggregated dynamically after the configuration . The server/switch should
support standard IEEE 802 .3ad Link Aggregation Control Protocol (LACP) on the links connecting DT switches . It
is assumed LACP on the servers are configured manually on the server with a list of links to be part of the LACP
trunk .
DT offers load balancing of traffic over multiple physical links . From the server to the switch, the traffic is
balanced according to the load-balancing scheme configured on the server NIC . From the switch to the server,
traffic is balanced according to the MAC destination address (DA) and source address (SA) pair .
Two DT switches can be connected via only one Inter-Switch Connection (ISC), and DT ports can be connected
only to servers . Following is the topology supported .
Figure A10.
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