Viper SC+™ IP Router for Licensed Spectrum PN 001-5008-000 Rev. C
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PLC LADDER LOGIC ON RESTART OPENS ALL CO NNECTIONS AT ONCE INSTEAD OF SEQUENTIALLY
When the PLC ladder program is set up to have at startup all write message rungs set to true, all TCP connections are
triggered “simultaneously.” This creates an overload of TCP SYNs and somewhat could congest the on-air traffic
depending on the system.
It is recommended to setup the ladder write message rungs not to start up simultaneously. Write messages should be
setup to open the TCP connection sequentially. For more information it may be required to contact your PLC provider.
VIPER GENERAL SETUP WITH PLCS
SET UP VIPER IN ROUT ER MODE INSTEAD OF BRIDGE MODE
Note:
Viper Bridge Mode cannot filter keep-alive and cannot operate in TCP proxy mode.
If the system has very few units and few messages Viper Bridge mode could be used. But for larger systems and PLC
doing many keep-alives, or on-air network being contentious, it may be required to use router mode. Router mode
allows retransmission of messages lost due to on-air contention. Bridge mode only does broadcasts without retries. In
Bridge mode the application needs to retry lost messages.
FILTERING TCP KEEP-ALIVE WITH VIPER TCP PROXY MODE
When using TCP protocol and having PLCs where the TCP keep-alive rate cannot be controlled, it is important to enable
Viper TCP (OIP proxy) mode. This requires that all Vipers are configured in router mode (Viper Bridge mode cannot
filter keepalive and cannot operate in TCP proxy mode).
Note:
For PLCs where the keep-alive can be controlled and are required, set keep-alive to 4 minutes.
One of the Viper's TCP proxy mode usages allows filtering of keep-alive messages and prevents them to be sent over
the air. Without this filtering, several PLCs sending keep-alive messages could easily load the on-air network.
If TCP Proxy mode is not enabled, see documentation earlier in this user manual about using the Viper Web interface to
enable it. By default Viper proxy mode is enabled. See the RF Network Settings » RF Bandwidth Management tab. Also
see RF Network Settings » Neighbor Table (Connectivity Status) to make sure that neighbors are configured with the
proxy attribute.
REPLACING OR RESETTING A VIPER USING PRO XY MODE WITHOUT REST ARTING POLLING
When replacing or resetting: a remote Viper, a Viper used as a repeater, or even a master Viper connected through a
switch, the Viper proxy context is lost. The Viper will reestablish proxy automatically.
ALLEN-BRADLEY PLC FOR VIPER SYSTEM
This guide is intended to assist with Allen-Bradley MicroLogix 1400 and 1100 communication setup between master
PLC and remote PLC using an Allen-Bradley TCP protocol between PLCs. Some information may apply for the Allen-
Bradley SLC 5 PLC.
