We recently performed an in-place upgrade of a 2008 R2 file server to 2012. For the most part things went well, but we have been unable to replicate with our only 2003 R2 file server with DFSR (other replica partners are 2008, 2008 R2 and 2012). The 2003 server logs successful 5004 events indicating a successful inbound connection from the 2012 server, but the 2012 server logs a 5002 with an error code 5 (access is denied).
I have checked the firewalls on both servers and the firewall in between and confirmed the two servers are communicating successfully. I completely reset the DFSR volume on the 2003 server (the 2012 server is our hub and is successfully replicating with four other servers), but the problem persists. I installed all the DFSR hotfixes for 2003 R2. Both servers are on the same AD domain and connected via a 10Mbps MPLS.
My best guess is that there is a permissions or rights setting causing the connection to be denied, but nothing has changed on the 2003 server recently, so perhaps there is a new security setting on 2012?