Update Vm Mac Address For Software Licensing

Jan 18, 2013  a) Turn off the virtual machine, allocate a static MAC Address that does not belong to Hyper-V's dynamic MAC address range, then restart the virtual machine. B) Increase the range of MAC addresses by using one of the following methods, by modifying the fifth and/or the sixth octet of the default dynamic MAC address range. May 03, 2014  VMware ESX Server virtual machines do not support arbitrary MAC addresses, hence the above format must be used. As long as you choose a hex value that is unique among your hard-coded addresses, conflicts between the automatically assigned MAC addresses and the manually assigned ones should never occur.

Obvious disclaimer: Using the information below to circumvent the license validation mechanism of a commercially licensed software product is almost certainly illegal in your city, state, nation, tribe, or religiously fundamental militia.

Let’s say you’re a software developer putting the finishing touches on a product that’s due to go to market shortly. The product is licensed on a per-machine basis, and you’re responsible for designing and implementing the license validation mechanism.

You are in an unenviable situation. It is 2015, and the concept of a machine has evolved from a static, hardware-based entity into an ephemeral, virtual one. In all likelihood, your customers will run your product on x86 virtual machines rather than AIX appliances. The VMs may be onsite, they may be hosted by a third-party service provider, or both. One thing is certain: basing your license validation mechanism on the static properties of an inherently ephemeral, virtual machine will introduce you to a world of hurt. When your customers replace an old VM with a new one, the new VM will, in all likelihood, have a different MAC address, and may have a different IP. If you base your license validation mechanism on MAC addresses, you will face a stream, maybe even a flood, of requests by customers to associate a new MAC address with an existing license. Those requests will take time and money to process and validate.

What’s more, MAC addresses can be spoofed at the operating system level. If your license validation routine checks for a static MAC address attached to a license, and I buy a license for MAC address ea:04:89:05:02:58, I would not be able to run your software on my Debian machine possessing the following network interfaces: Change default browser.

This machine has a single Ethernet interface with the usual loopback interface, about as simple as it gets. The eth0 interface has a MAC address of 43:87:35:96:2e:75 burned into it; assuming no bugs in your code, your software will refuse to start when I run it on this machine. But if I modify the eth0 entry in my /etc/network/interfaces file to the following:

and bring the eth0 interface down and back up, ifconfig will show that eth0’s MAC address has been changed accordingly:

Vm software download

Now if I try to run your software, license validation will succeed. But depending on the circumstances, this may cause more problems for me than it solves, notwithstanding questions of legality. If I spin up multiple machines with the MAC address overridden in this fashion, and these machines are on the same network, the entry for ea:04:89:05:02:58 in the router’s MAC table will change continually as each machine sends frames across the network. Thus, only one machine will ever be reachable at a time.

Furthermore, some enterprise environments maintain a whitelist of MAC addresses and associated metadata; although implementations of this whitelist and associated software vary, the point is usually to prevent any unknown NICs, or duplicate (spoofed) NICs, from ever achieving network connectivity.

At this point, I could admit defeat, open a support case with you, and request that the license I bought have the associated MAC address changed. This likely forces me to wait a few hours at best and a day or more at worst. This isn’t a big deal if I’m required to do this on an infrequent basis, but if I have to do this often, it will introduce significant delays to my otherwise instant provisioning and configuration procedures.

Not wanting to deal with the deterimental consequences to my own operations as a result of your inflexible license validation scheme, I go back to the technical drawing board. Rather than override the MAC address on eth0 itself, I create a new MAC VLAN interface on my machine:

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# ip link add link eth0 address ea:04:89:05:02:58 vlan0 type macvlan

I’ve named this new interface vlan0 and given it the MAC address that’s associated with the license I currently have. A MAC VLAN is conceptually layered atop an existing interface, and can have its own MAC address and IP address. Traffic on this particular interface will be sent to eth0. After bringing the new interface up:

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# ip link set up dev vlan0

running ifconfig shows the newly added interface as follows:

This interface is completely invisible to the outside network. The router doesn’t see it, and any enterprise MAC address filtering software will not see it. When frames are emitted on vlan0, they will in turn be emitted by eth0; when they are forwarded across the network, their source MAC address will be that of eth0, not of vlan0.

But how to emit frames on vlan0 in the first place? You will need to modify your IP routing table. Running ip route will show something along the lines of:

These are the standard default gateway, zeroconf, and link-local routing entries. They are all associated with eth0. I can modify these entries to use vlan0 instead (note that order is important here: you must change the link-local entry before you change the default gateway entry, otherwise you will encounter an error):

Software

Update Vm Mac Address For Software Licensing Center

A quick check of tcpdump -i vlan0 shows that traffic is now being routed through the interface successfully. Now, any application that queries for the system’s MAC address will be presented with the value ea:04:89:05:02:58, allowing me to use my current license on the machine without running into the problems caused by overriding the physical interface’s MAC address directly.

I present the narrative above not from the adversial perspective of an illicit consumer, but as a software developer that fails to see the efficacy of a license validation mechanism that uses MAC addresses. It is effectively pointless. The validation code has to be maintained, the licenses have to be generated and recorded, changes to the licenses have to be triaged by support personnel - but where are the benefits?

Support doesn’t benefit, because there’s nothing to be gained from having paying customers submit their licenses with every SR. Customers certainly don’t benefit, as license files are yet another resource for them to monitor and acquire. That leaves the billing department. If the software license agreement stipulates that the company is to be paid by the customer for each per-machine license, I can see how that simplifies billing significantly. Yet the narrative above shows how easily falsifiable MAC addresses are, which means billing is in turn relying on a falsifiable metric for payment purposes.

Most, if not all, customers are going to play by the rules. The risk is that potential new customers with more modern computing environments and better technical discernibility will choose to take their business elsewhere. The days of per-CPU, per-core, and per-machine license agreements are rapidly fading, and for good reason. Usage of a licensed application cannot credibly be measured in CPUs or machines, especially in organizations with multiple replicated environments for development, testing, and production. Add in the historically new ability to dynamically expand and contract environment footprints in terms of machines and data centers, and per-machine licensing becomes uneconomical and impractical.

Per-machine licensing is indicative of short-sighted management, and leads to technical implementations like MAC address validation that completely fail to accomplish the goal of enforcing one license per machine in the first place. If licensing costs are to be tied to a metric, an auditable or puplicly disclosable value should be used, such as employee count, quarterly revenue, quarterly profit, etc. Adopting such a licensing scheme eliminates all of the inconveniences of per-machine licensing for both provider and consumer, along with the temptation to employ technical circumventions such as the one detailed here.

The Cisco CSR 1000v maps the GigabitEthernet network interfaces to the logical virtual network interface card (vNIC) name assigned by the VM. The VM in turn maps the logical vNIC name to a physical MAC address.

Vm Software Download

When the Cisco CSR 1000v is booted for the first time, the router interfaces are mapped to the logical vNIC interfaces that were added when the VM was created. The figure below shows the relationship between the vNICs and the Cisco CSR 1000v router interfaces.

After the Cisco CSR 1000v boots, you need to display the mapping between the logical interface on the router with the vNIC and the vNIC MAC address using the show platform software vnic-if interface-mapping command. The display for this command is different depending on your Cisco IOS XE release version. https://thisgol.netlify.app/impro-visor-music-notation-software-mac.html. (Note: For Cisco IOS XE Release 3.11 or later, the GigabitEthernet0 interface is no longer supported.)

The vNIC name shown in the display is a logical interface that the Cisco CSR 1000v uses to map to the interface on the hypervisor. It does not always map to the corresponding NIC name added during the VM installation. For example, the logical “eth1” vNIC name in the display may not necessarily map to “NIC1” that was added in the VM installation process.


Caution
It is important that you verify the interface mapping before you begin configuring the Gigabit Ethernet network interfaces on the Cisco CSR 1000v. This ensures that the network interface configuration will apply to the correct physical MAC address interface on the VM host.

If you reboot the router and do not add or delete any vNICs, the interface mapping remains the same as before. If you reboot the router and delete vNICs, special care must be taken to ensure that the configuration for the remaining interfaces remains intact. For more information, see Adding and Deleting Network Interfaces on the Cisco CSR 1000v.


Note
In Cisco IOS XE Release 3.10S and earlier, the first vNIC added is automatically mapped to the GigabitEthernet0 management interface. All subsequent vNICs added are mapped to router interfaces. Support for the GigabitEthernet0 interface was removed in Cisco IOS XE Release 3.11S.