East-West service insertion refers to the ability to insert security services, such as firewall and intrusion detection and prevention, between virtual machines (VMs) that are communicating within the same logical network.
One of the insertion points for East-West service insertion is the virtual network interface card (vNIC) of the guest VM. The vNIC is the virtual representation of a physical NIC on a VM, and it connects the VM to the virtual network. By inserting security services at the vNIC level, traffic between VMs can be inspected and secured before it reaches the virtual switch.
VMware NSX-T Data Center documentation https://docs.vmware.com/en/VMware-NSX-T-Data-Center/index.html VMware NSX-T Data Center Security documentation https://docs.vmware.com/en/VMware-NSX-T-Data-Center/3.1/com.vmware.nsxt.security.doc/GUID-8F7C8B70-F1A6-4F31-8D6C-A0A9B9C9A9D3.html