Mount Mac OSX server NFS from Linux <krb5> LDAP?

I'm trying to mount an NFS share from Fedora 16. The server is Mac OS X Server, set up by my coworker. I believe it requires Kerberos/LDAP authentication, so I would start the (probably arduous) process of getting that figured out, but there's some things I don't understand.

showmount -e SERVER gives the expected share and IP permissions, and has <krb5>.

# sudo mount -v SERVER:SHARE MNT 
mount: no type was given - I'll assume nfs because of the colon mount.nfs: timeout set for Wed Nov 28 15:10:32 2012 
mount.nfs: trying text-based options 'vers=4,addr=XXX.XXX.XXX.XXX,clientaddr=XXX.XXX.XXX.XXX' mount.nfs:
mount(2): Protocol not supported 
mount.nfs: trying text-based options 'addr=XXX.XXX.XXX.XXX' mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying XXX.XXX.XXX.XXX prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17 
mount.nfs: trying XXX.XXX.XXX.XXX prog 100005 vers 3 prot UDP port 676 
mount.nfs: mount(2): Permission denied mount.nfs: access denied by server while mounting SERVER:SHARE

This confuses me a little because if I was getting rejected because of Kerberos I would have expected it to be vers=4?

I've also seen posts that say that I need to have the same uid but that doesn't make too much sense.

Should I just go ahead and try to get some credentials into LDAP? If so is there a pointer for how to do this in the context of Mac/Linux? Or is there some other debugging I should do first?

First, check klist for a TGT, if not kinit;klist.

Try adding -o sec=krb5 to the mount command i.e

sudo mount -o sec=krb5 -v SERVER:SHARE MNT

Check your /etc/krb5.conf to ensure everything is set up right for your environment