Optimum Internet Support for Lyon Rental Properties. (Faculty / Staff) Overview This information applies to Faculty or Staff currently living in Lyon owned rental properties. Tenants must call Optimum directly for internet or Cable TV support. Instructions Optimum has a number tenants to call for support. This type of support is called MDU support. The MDU support number is 1-866-229-8750 If the support agent asks for an account number you must specify you are a rental tenant and you don't need to the account number and only the address of the property should be needed to schedule service or get support. Mention you were given this number as MDU support for tenants.