The MOUNT protocol is used in NFS version 2 and 3 to find the initial filehandle for the mountpoint.
The protocol is no longer used in NFS version 4 since this functionality has been incorporated into the NFS protocol itself.
Since MOUNT is not using a fixed standard port it is difficult to use MOUNT and thus NFS through a firewall. Some vendors such as SUN do however implement extra features to the NFS protocol to allow to eliminate the need of the MOUNT protocol (mount option public). This allows a client to mount an NFS share through a firewall but does not address the issues with the NLM lock management protocol nor the NSM status monitoring protocols making this workaround only useable for read-only filesystems.
The MOUNT protocol is a support protocol for versions 2 and 3 of NFS. (It is also used for version 1 of NFS but no one I know of have ever seen such captures).
Until today there has been 3 different versions of the MOUNT protocol, version 1, 2 and 3. These versions are virtually identical as far as normal unix NFS servers and clients are concerned and only differ by version 2 and version 3 removing some of the procedures that are never used anyway.
The MOUNT dissector is fully functional. The Service Response Time statistics feature in both Wireshark and TShark can calculate response time statistics for this protocol.
There are no preference settings for the MOUNT protocol.
Example capture file
A complete list of MOUNT display filter fields can be found in the display filter reference
Show only the MOUNT protocol:
You cannot directly filter on the MOUNT protocol while capturing. Since MOUNT does not use a standard port you can not capture on a specific port either.
RFC 1813 NFS Version 3 Protocol Specification - contains an appendix for the MOUNT v3 protocol
On Un*xes that include RPC support, the following tools are usually part of the OS:
- rpcinfo can be used to "ping" the MOUNT service on a server.
- showmount can be used to interrogate a server, using the MOUNT protocol, to find out which shares are exported and which shares are mounted by which clients.