Why Can't These Two Computers Talk to Each Other

The task of this one day lab was to see why 2 computers, directly connected to eachother through ethernet, were unable to ping each other.
Focusing mainly on the bottom 3 OSI layers: Physical, Datalink, and Network, each of these could of caused the computers to be unable to ping:
Physical:
The wires bad, the NIC isn't working, or another hardware issue
Datalink:
IP is unable to be resolved into a MAC address.
Network:
device is not getting an IP, or the IP's of the two devices are in different ranges even though they are on the same network.

The failure points expected were mostly related to layers 2 and 3, being:
Datalink not being able to resolve the mac address from an IP, or similar issues with IP resolution. This is kind of similar to how DNS servers sometimes don't work where IPs do
Network is probably the most likely of all, if the IP it assigns is self assigned then the other computer will not be able to resolve it, and therefore fail.

Checking my own IP, I got 10.12.26.30. the ethernet was also confirmed as working as it shows state UP, and I have a mac address of 46:d0:1e:a2:d4:12

When attempting to ping my partner, it failed. It failed with the error "Destination Host Unreachable", which indicates that it was unable to find the host name (mac address) of the IP. This indicates that the issue in connection is with layer 2, as the ARP (Address Resolution Protocol) is not functioning. 

The two IPs got earlier were 10.12.26.30 for myself, and 10.12.25.170 for my partner. While these IPs are not identical, they do share the same range, which should be a positive sign that should mean that they are able to connect to each other. Additionally, the ping failure above also suggests that it is not an issue with the network layer, but rather the datalink, as Destination Host Unreachable is representative of finding a mac address failure. Another issue that could be IP related is a common issue, being deciding on Shared vs Bridged mode. for this, bridged mode was used to be a more similar network, and using it gave us similar IP ranges, but also it is notoriously slow and spotty even in the best cases, which could of lead to the bridged failure.

Seen from the ping above, it failed 12 times, all due to "Destination Host Unreachable." This suggests that it is an issue in finding the destination host's mac address, lending to the theory that it is an issue in layer 2. 

The outcome of this lab was a success at failure. The issues were not with physical, as IP a shows (state UP), highly likely that the Datalink layer was the issue, with it being unable to resolve to a MAC address, and the Network layer could also be causing issues as the VM is a virtual network running connected to a real network. In the reflection section, the fixes are described.