Moxa CN2650-16-2AC-T Terminal Server Specification Guide

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Terminal Servers

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CN2600 Series

Redundancy is an important issue for industry, and several different 
solutions have been developed to prevent damage caused by 
equipment or software failures. “Watchdog” hardware is required to 
utilize redundant hardware, and a “Token” switching mechanism is 
required for software. The CN2600 terminal server uses its built-in 
Dual-LAN ports to implement a “Redundant COM” mode that keeps 
your applications running smoothly.

The CN2600 has two separate LAN ports that can be connected to 
separate LAN networks. Dual-LAN redundancy involves setting up two 
separate physical networks to connect the PC host with the CN2600. 
In this case, the PC host must also be installed with two LAN cards. If 
one of the networks fails, the PC host will still be able to communicate 
with your serial devices over the redundant LAN.

Moxa provides an easy-to-use function, called “Redundant COM,” for 
duplicating the CN2600’s data transmissions. In this case, when the 
CN2600 receives a data packet from a connected device, the CN2600 
will automatically duplicate the packet and send both packets over 
separate LANs. If either of the two LANs fails, the other LAN will 
continue transmitting packets between the serial devices and the host 
to prevent lost packets. The Moxa driver is programmed to compare 
packets received from the two LANs, and then discard duplicate 
packets to prevent the host AP from receiving the same packet twice. 
The Redundant COM function not only prevents data loss when one of 
the LANs fails, but also prevents the host AP from receiving garbage 
data.

The CN2600’s dual LAN cards can also be used to set up “dual-host” 
redundancy. In this case, both networks (LAN A and LAN B in the 
figure) are connected to two different hosts. If either of the two hosts 
shuts down unexpectedly, the other host will continue transmitting 
packets to (and receiving packets from) the serial devices connected 
to the CN2600.

Host

Data A

LAN A
LAN B

Data A

Data A

Serial

Data A

Data A

Host

LAN A
LAN B

Data A

Data A

Serial

Data A

Host 1

Data A

LAN A
LAN B

Data A

Host 2

Data A

Data A

Data A

Serial

Data A