It also requires an active and valid at system date IT0000 and IT0001 as well as the travel infotype (IT0017 as mentioned) whilst cost center can be defined in either IT0001/IT017/IT0027 and Travel also checks payroll integration during settlement process and posting to FI (a dummy payroll record will suffice if no payroll integration is required)
I moved this to the Travel Management forum also but please do check out the external wiki and SAP help as this is explained in more detail