Contemporary Control Systems Compact Managed Switches Software Manual for Console Access - Manual (Page 13)

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4.3.3 Configure Port Trunking (Copper Ports Only)
Port Trunking allows two or more of ports 1–8 to be grouped with the resulting group
behaving as a single logical link. The 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 7 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 7 — Port Trunking