This article explains why VM's on the same subnet cannot communicate with each other
VM1 has assigned IP 10.1.1.4
VM2 has assigned IP 10.1.1.5
VM1 and VM2 cannot ping each other
No FIP is assigned
No Router/L3 is configured
Some of the reasons are:
1. Likely you may have created multiple "shared networks" using the "same subnet range". These shared networks are in separate Projects for example but having the same network configuration say 10.1.1.0/24.
Net1 is configured on First Shared Network on Project1 as 10.1.1.0/24
Net2 is configured on Second Shared Network on Project2 as 10.1.1.0/24
VM1 is configured using Net1
VM2 is configured using Net2
These two VM's are on different namespaces although the IP addressing looks as if they are on the same network but they are not, hence the issue. Please note for this scenario there is no router/L3 configured.