Cannot run a job to update table on a linked server

I am running SQL Server 2012 on a server (server 1) and have set up a job to run a stored procedure which will summarize data from a series of tables and update a table on a linked server (server 2) which is also SQL Server 2012. I can successfully run the stored procedure on it's own, but when the scheduled job runs, I get the following error: >Executed as user: NT AUTHORITY\NETWORK SERVICE. The OLE DB provider "SQLNCLI11" for linked server "222.222.222.222" reported an error. Authentication failed. [SQLSTATE 42000] (Error 7399) Cannot initialize the data source object of OLE DB provider "SQLNCLI11" for linked server "222.222.222.222". [SQLSTATE 42000] (Error 7303) OLE DB provider "SQLNCLI11" for linked server "222.222.222.222" returned message "Invalid authorization specification". [SQLSTATE 01000] (Error 7412). The step failed.,00:00:00,16,7412,,,,0 I suspect this is a security issue, but cannot find the settings that will let me run this.