The deal also comes with a three-year extension option. Under the terms of the contract, CSC will provide midrange services and Oracle ERP support.
The midrange work includes server maintenance and management, datacentre hosting, security, disaster recovery planning and storage area network management.
Around 70 members of Network Rail's current IT support team will transfer to CSC, including employees from previous contract incumbents.
Catherine Doran, director of information management at Network Rail, said, "We have always been clear that our preferred supplier in this area must engage in our development and change programme, as well as keep the critical systems running.