There are different perspectives into this question:

1) HostA and HostB are on the same VLAN

2) HostA and HostB are on different VLANs



Let's consider router on a stick for inter-vlan routing.

In the first case, since the devices are on the same subnet, the traffic will not pass through a L3 device, only through the switch itself, so the source and destination MAC Addresses and IP will look like this:

Source MAC: HostA MAC

Source IP: HostA IP

Destination MAC: HostB MAC

Destination IP: HostB IP



If the hosts are on different VLANs/subnets, then the traffic will go through the L3 device (router in this case).



Inbound traffic:

Source MAC: HostA MAC

Source IP: HostA IP

Destination MAC: Router's MAC (specifically for the subinterface that is used to route the packets off this subnet)

Destination IP: HostB IP



Outbound traffic:

Source MAC: Router's MAC

Source IP: HostA IP

Destination MAC: HostB MAC

Destination IP: HostB IP



HTH

Good luck!