[CentOS] Can I force yum to only use http.

Our outsourced IT department has decided to use white listing on the firewalls for outbound ftp.  I was given a list of sites our lab had accessed via ftp and eventually tracked them down to Linux machines running yum.  They are all CentOS 5 or 6 with a smattering of 7.  It is impractical to list all the possibilities since they change on a regular basis.  Also any 3rd party repos we need are another ball of wax.



Various Google searches and the manual page have not shown me how to avoid using ftp mirrors.  I have considered taking out the ftp-proxy information so that the ftp cannot get out, but I suspect it will just hang waiting for a response.



Does anyone have any suggestions on ways to tell yum not to use ftp as the download mechanism?



Thank you in advance.



Bob