May I ask, since the PLCs are connected to the host computer via Ethernet ports, what is the role of the router?
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I know that if an Ethernet connection is used to link the PLC and the host computer, a router is needed in between. A colleague asked me how this router works, and why it’s possible to connect two devices using this router, but it’s not possible to establish a connection by simply plugging in an Ethernet cable. If there are two laptops, with their IPs set within the same range, can they be connected directly via an Ethernet cable without needing a router? I’m a bit stuck and would like to ask everyone about this principle in order to get some clarification. Also, can a hub be used instead of a router?
This post was last edited by queny on 2016-3-22 at 11:48. Your PLC and host computer must be quite old; many Ethernet devices from back in the day required crossover cables in order to connect directly to a PC, as straight-through cables didn’t work； Modern network cards and Ethernet devices all have self-identification, so there are basically no situations where a direct connection cannot be established. My understanding is that the role of the router you mentioned is to convert between cross-linked cables and directly connected cables; this router can be replaced with a switch, but not with a hub.
The host computer is quite old. Devices cannot be recognized when connected directly via an Ethernet cable without a router; using a router works.
A straight cable won’t work; try a crossover cable