some of the ports of slm224g2 switch are connected to the ethernet ports of STM equipment to connect to remote PCs. we have connected to 9 such remote PCs. we could communicate with 8. 9th one we are unable to connect. all combinations tried. we r not successful. always the same set of 8 are working. if we use d link un managed switch the 9th one is working. where could be the problem? please suggest.