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3 configure port trunking (copper ports only), On 4.2.1.3) – Contemporary Control Systems Compact Managed Switches Software Manual for Console Access User Manual

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TD020850-0MG

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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

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