NFS Mount Fails "[nfs] Rejected request from on unprivileged port 51405 for program mountd procedure 1."

Whenever I try to mount an NFSv3 share on Isilon I get the following error:

[nfs] Rejected request from <ip> on unprivileged port 51405 for program mountd procedure 1.

I have tested two different clients and the same issue persists.

I am using the following command on the client to mount the export. Even when I omit the options it fails. I have tried mounting as root and as a normal user.

mount.nfs -o 'vers=3,tcp' <access zone ip>:<path> /mnt/test

On Isilon I have done the following to try to make it work:

• Added all permissions to the share directory (owner: root, group: wheel)
• Changed root user mapping from nobody to root
• Added export client IP to Always read/write and root clients
• Set export security types to UNIX (system)
• Confirmed that rpcbind, nfs, mountd and nlockmgr are running on all nodes

The version of Isilon I am using is 9.1.0.0.