KVM-VM-1 had the IP address 192.168.42.10 so lets change it to 192.168.42.42 by editing the /etc/network/interfaces on our Ubuntu-Server VM:Īt this point we only need to reload the network configuration, for example by rebooting the VM, and all the restrictions by the DFW will be gone. However, in the default configuration of NSX-T using the default Switching Profiles, we can easily bypass the DFW restrictions by changing the IP address within the VM. Now, we are not able to ping from KVM-VM-1 to KVM-VM-2 anymore:īypassing the NSX-T Distributed Firewall (DFW) Now lets create a firewall rule which drops all traffic from KVM-VM-1 to KVM-VM-2: We then create two groups with the same names and make all VMs with the respective tag member of the corresponding group as shown below for the KVM-VM-1 group. NSX-T Distributed Firewall (DFW)įor the DFW functionality, we assign the tag KVM-VM-1 to the first VM with the IP address 192.168.42.10 and the tag KVM-VM-2 to the second VM with the IP address 192.168.42.11. In TOFU mode, when an address is discovered and added to the realized bindings list, that binding remains in the realized list forever. NSX-T will use ARP snooping to discover these IP addresses and add them to the Realized Bindings of the corresponding logical switch port as shown below for the first VM:Īs stated in the documentation, this is done based on trust on first use:īy default, the discovery methods ARP snooping and ND snooping operate in a mode called trust on first use (TOFU).

Within the VMs, we manually configure the IP addresses 192.168.42.10 and 192.168.42.11 respectively. So lets assume we have 2 VMs on 2 different KVM hypervisors both connected to the same logical switch. This can be restricted by configuring the DFW based on tags you assign to the virtual machines. Within logical switches and routers, all network traffic is allowed by default. The hypervisors then use an overlay network to forward the VM traffic between them and configure the local virtual switches on the hypervisors to forward the network traffic accordingly.

In NSX-T, you can interconnect different hypervisors (currently: ESXi and KVM) as so-called Transport Nodes and then configure logical switches and routers across the VMs running on different hypervisors. In short, the Distributed Firewall (DFW) of NSX-T can be easily bypassed in the default configuration because it only works effectively if at the same time, the SpoofGuard feature is enabled on all logical switch ports which is not the case by default. Because many of our customers start with transitioning to NSX-T, we want to share this with you. We recently came across an issue when playing around with VMware NSX-T which not anyone might be aware of when getting started with it.

Firewall on mac