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ISC requests IT service providers share their self-assigned non-routable IPv4 address space

As ISC moves forward on a major upgrade of the Network Names & Numbers service (“DDI replacement”), we believe there is a need and opportunity to manage IP address space more comprehensively across the University.

IT staff at Penn understand well that PennNet routable IPv4 address space is a valuable and increasingly scarce shared resource. ISC tracks its use centrally to avoid conflicts, reduce waste, and to promote the orderly operation of PennNet. What may be less well understood is that there is a real and growing need to manage non-routable IPv4 address space in the same manner.  

Non-routable IPv4 address space is defined in RFC 1918. It is also known as “private” because network operators may deploy it internally, independent of public address registries and Internet Service Providers. It is comprised of the following blocks:

     10.0.0.0/8
     172.16.0.0/12
     192.168.0.0/16

Although ISC has centrally allocated some parts of this address space, there has been relatively little effort to coordinate its use overall. However, as the demand for address space continues to rise, so has the need to be able to route between previously isolated networks across PennNet and between Penn and its cloud providers. Consequently, IT service providers across campus are faced with the risks and disadvantages of inconsistently managed IP address space. When there is a conflict between two or more address blocks, IT staff must undertake a disruptive and labor-intensive renumbering effort, or implement workarounds that tend to be costly, fragile, and restrictive.  

To avoid this, we strongly encourage all IT service providers on campus to provide ISC a list of all non-routable address blocks that are being used in campus or cloud via Support Center using the "General Client Care Request" tile, or mail help@isc.upenn.edu This will help us to identify any current conflicts or reserve this address space for an IT provider to avoid future conflicts. Once we have completed this effort, it is important for IT providers to coordinate future IP address space management with ISC to ensure that these blocks continue to be well-managed.

In providing these address blocks, please include the following subject: “DDI – self-assigned IPv4 address space” to allow us to better coordinate this work.