Sorry I misspoke, it's in DefaultTransport:Outgoing:send

From...

if (targetNetworkNumber != Address.LOCAL_NETWORK && targetNetworkNumber != Address.ALL_NETWORKS && targetNetworkNumber != network.getLocalNetworkNumber()) { // Going to a specific remote network. Check if we know the router for it. linkService = networkRouters.get(targetNetworkNumber); if (linkService == null) handleException(new BACnetException( "Unable to find router to network " + address.getNetworkNumber().intValue())); }

to...

if (targetNetworkNumber != Address.LOCAL_NETWORK && targetNetworkNumber != Address.ALL_NETWORKS && targetNetworkNumber != network.getLocalNetworkNumber()) { // Going to a specific remote network. Check if we know the router for it. linkService = networkRouters.get(targetNetworkNumber); if (linkService == null) { handleException(new BACnetException( "Unable to find router to network " + address.getNetworkNumber().intValue())); return; } }