Contemporary Control Systems Compact Managed Switches Software Manual for Web Browser - Manual (Page 19)

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4.4.2 Configure Trunking
Port Trunking allows two or more ports to be grouped with the resulting group behaving
as a single logical link. A managed switch supports multiple trunks — each constructed
of 2 or more fixed physical ports.
To keep frames in order, packets with the same source/destination MAC addressing are
sent over the same trunk path — but the reverse path may follow a different link
because a hash algorithm is used to balance the load between links in a trunk.
Adding more ports (links) to a trunk group will increase the communication bandwidth
between two switches. Either one or two trunk groups can be defined — but always from
among ports 1–8. Even with a 16- or 24-port unit, only ports 1–8 support trunking.
Port Trunking on managed switches from Contemporary Controls also provides redundancy
with a fast recovery time (several milliseconds). If a link in the trunk group is lost, the
remaining links immediately take over and maintain communication between the switches.
Figure 14 illustrates three two-link trunks (A, B and C) connecting two computers
through four switches. This configuration could sustain a link loss in Trunk A, but within
milliseconds a redundant data path would be reconstructed between the two computers.
A similar recovery would manifest for a link lost in Trunk B or C. Indeed, even multiple
link losses — one in each trunk group — would not disrupt communication between the
two end stations except for the brief recovery time.
Figure 14 — Trunking
Figure 15 displays a sample Configure Trunking screen with two trunk groups defined.
The sample shows that only Group 1 is currently active. It would be permissible for
both of these two sample groups to be enabled simultaneously — but only because they
do not have any ports in common (overlapping ports).
Figure 15 — Configure Trunking
(copper ports only)