As a network or cloud administrator in VMware environment, we would like to have the same capabilities we’ve got in a physical network. One of the most important tasks is network traffic monitoring and inspection control. Let’s say you want to install a network Intrusion Detection System (like SNORT) to monitor the traffic of a specific Virtual Data Center in vCloud environment that is translated to monitoring a specific VLAN or port group in VMware vSphere. Fortunately, VMware 5.x provides these features but apparently implementing these features is beyond VMware vCloud Director operations and it’s part of infrastructure administration tasks introduced in vSphere 5.x.
Since normally there is a port group in Distributed Virtual Switch defined by vCloud Director for each virtual data center, let’s talk about port groups in VDS. You may have noticed that when you want to create a port group in a distributed switch, you can define some security policy and one of the policies is enabling ‘Promiscuous Mode’. This is exactly equivalent to enabling promiscuous mode in a physical switch. So, as shown in the following picture, a port group can be edited to enable this mode (in vSphere Web client).

The only concern is that promiscuous mode should be defined on a port group or the whole distributed switch and not on a particular port. Doing this will cause all the traffic to be forwarded to all of the VM’s in that port group! and apparently it’s a security risk because we would like to forward the traffic to only one specific VM (port) which is our IDS. A work-around here would be to define a new port group with the same VLAN ID of the port group/VLAN we would like to monitor with the exact same configuration, then enable promiscuous mode for this newly defined port group and place the IDS VM in this port group. Because VLAN ID is the same, only IDS VM would see all the traffic. That’s an easy trick! BUT I don’t know how this trick works in some vCloud port groups that use VCDNI-backed port groups instead of VLAN-backed network pools because as I understood, VCDNI is kind of encapsulation introduced by vCloud Director and I’m not sure if a port group that is created inside vCenter can decapsulate packets. I didn’t find enough information, so I will test this out and report it in this blog.

Another approach is to use Port Mirroring feature of a VDS. Using this method it’s possible to specify source ports which need to be monitored and destination port/ports where IDS is located.

This solution is explained in detail in the following link:

vSphere 5.1 – VDS Feature Enhancements – Port Mirroring