I frequently see customers asking about how to quickly enable communication between their virtual machine resources within a security group.

For example, how do you allow two web servers to talk to each other freely within a security group?

The answer can be found in Group Access Rules

To enable them, choose the security group that is related to the virtual machines you want to enable group level communication, then on the right-most column, “Enable” the protocol you’d like - TCP, UDP, or ICMP.  All three can be enabled for essentially open communication within a group.