User guide

20 User Guide
Back-to-Back Application
A typical application of the “redundant twister” is to use them in pairs to extend a
network’s reach between two remote devices. In the back-to-back setup, both
primary ports are linked to each other and both secondary ports are linked as shown
in the figure below.
Primary Links
Secondary Links
Main Links
Server Cluster A Server Cluster B
“redundant twister”
“redundant twister”
In a back-to-back application, make sure that the following switches are enabled on
both “redundant twister” units:
1. RED MODE switch. Sets the “redundant twister” to operate in Dynamic
Recovery Mode. In this mode, the secondary port automatically becomes the
active port if the primary link is lost and the secondary link is present.
2. TX BOTH switch. Allows the “redundant twister” to transmit data on both the
primary and secondary ports simultaneously. The units must have this switch
enabled because they cannot determine which port is active on the other
“redundant twister”.
3. LINK BOTH switch. This allows link pulses to be sent out both the primary
and secondary ports. If neither secondary port is transmitting link pulses and
one of the primary ports loses link, a switchover will NOT occur. A
switchover will occur only if the secondary port has link.