I am studying for CCNA certificate and wanted to know the actual difference between Hub-and-spoke and Star topologies. Could somebody explain me this as it looks identical to me.
Hub and spoke vs Star topology
topology
Related Solutions
Switch uses Layer 2 Spanning Tree Protocol to ensures a loop free topology for any bridged Ethernet network. So if yours IOT device will forward bridge protocol data unit (BPDU) accross, switch will maintain loop free topology. BPDU are transsmited accross local network to detect loops in network topologies. If BPDU won't be forwarded you can possibly have a loop. But effect of STP could be something like on this picture.
So two IOT boards would be able only to talk with DHCP server thru another IOT board.
I would have said they weren't so much ambiguous as badly drawn.
As you say, there are very few bus-topology wired ethernet networks these days. The main issue (with both diagrams) is that it looks like two connections go into one socket (eg the bottoms of the router and switches). I'm sure even these days you can get switches with 10base5 or 10base2 or AUI connectors, but I've never seen one. In the 1990s we used to use hubs with 16 port of 10baseT and one 10base2 BNC socket, and occasionally we used the BNC socket, such as during a transition to 10baseT.
On the assumption it's just a drawing issue ...
If you're drawing a diagram which needs to emphasise cabling, such as a patch diagram or physical layout, you might draw it more clearly like this:
More usually we hide the layer 2 detail of switches and draw something like this, where a given broadcast domain is conflated just into a fat line:
Hope that's helpful.
Best Answer
As already said in comments, they are the same.
I always prefer to use "star" to describe the topology to avoid any confusion with ethernet hub. Otherwise you might find yourself writing "The hub is a router and the spokes are hubs."