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3. VIPER
3.1. SETUPVIPERIN ROUTERMODE(INSTEAD OFBRIDGEMODE)
Info:ViperBridgemodecannotfilterkeepaliveandcannotoperateinTCPproxymode.
IfthesystemhasveryfewunitsandfewmessagesViperBridgemodecouldbeused.ButforlargersystemsandPLCdoing
manykeepalives,oron‐airnetworkbeingcontentious,itmayberequiredtouse
routermode.Routermodeallows
retransmissionofmessageslostduetoon‐aircontention.Bridgemodeonlydoesbroadcastswithoutretries.InBridge
modetheapplicationneedstoretrylostmessages.
3.2. FILTERINGTCPKEEPALIVEWITHVIPERTCP PROXYMODE
WhenusingTCPprotocolandhavingPLCswheretheTCPkeepaliveratecannotbecontrolled,itisimportanttoenable
ViperTCP(OIPproxy)mode.ThisrequiresthatallVipersareconfiguredinroutermode(ViperBridgemodecannotfilter
keepaliveandcannotoperateinTCPproxymode).
Note:ForPLCs
wherethekeepalivecanbecontrolledandarerequired,setkeepaliveto4minutes.
OneoftheViper'sTCPproxymodeusagesallowsfilteringofkeepalivemessagesandpreventsthemtobesentovertheair.
Withoutthisfiltering,severalPLCssendingkeepalivemessagescouldeasilyloadtheon‐air
network.
SeeViperusermanualandWebpagestoenableproxy.BydefaultViperproxymodeisenabled.SeeViperWebpage
Advancedsetup‐>OIPoptimizations.AlsounderNetworkmanagement‐>NeighborTables(neighbormanagement)make
surethatneighborsareconfiguredwiththeproxyattribute.
3.3. REPLACINGORRESETTINGAVIPERUSINGPROXYMODEWITHOUT RESTARTINGPOLLING
Whenreplacingorresetting:aremoteViper,aViperusedasarepeater,orevenamasterViperconnectedthrougha
switch,theViperproxycontextislostandwilloperatewithouttheproxybenefit.
ToreestablishTCPproxycontextfortheTCPconnection,thePLCneedstoclosetheold
TCPconnectionandre‐openanew
TCPconnection.ThereforenormallyafterdoingVipermaintenancethemasterPLCneedstoberestarted.FutureViper
firmwaremayreestablishproxyautomatically.
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