NFS Services Administrator's Guide (5900-1632, August 2011)

Sharing directories across a firewall using the NFSv4 protocol
NFSv4 is a single protocol that handles mounting, and locking operations for NFS clients and
servers. The NFSv4 protocol runs on port 2049, by default.
To override the default port number (2049) for the NFSv4 protocol, modify the port number for
the nfsd entry in the/etc/services file.
Configure the firewall based on the port number set.
Sharing directories across a firewall using the WebNFS Feature
The WebNFS service makes files in a directory available to clients using a public file handle. The
ability to use this predefined file handle reduces network traffic, by avoiding the MOUNT protocol.
How WebNFS works
This section compares the process of communication between an NFS client and an NFS server
across LANs and WANs. Table 5 compares the NFS session across a LAN with a WebNFS session
across a WAN.
Table 5 NFS Session Versus WebNFS Session
How WebNFS works across WANsHow NFS works across LANs
NFS servers register on port 2049. WebNFS clients contact
the WebNFS server on port 2049.
NFS servers must register their port assignments with the
portmapper service that is registered on port 111,
although the NFS server uses 2049 as the destination
port.
A WebNFS client can use the PUBLIC file handle as an initial
file handle, rather than using the MOUNT protocol.
The MOUNT service is not registered on a specific port.
The NFS client must use the portmapper service to
locate the MOUNT port. Once the port is located, the
client must issue a request for a file handle corresponding
to the requested path.
Figure 3 shows a sample WebNFS session.
Figure 3 WebNFS Session
Figure 3 depicts the following steps:
1. An NFS client uses a LOOKUP request with a PUBLIC file handle to access the foo/
index.html file. The NFS client bypasses the portmapper service and contacts the server
on port 2049 (the default port).
2. The NFS server responds with the file handle for the foo/index.html file.
3. The NFS client sends a READ request to the server.
4. The NFS server responds with the data.
Removing the additional overhead of the PORTMAP and MOUNT protocols reduces the binding
time between the client and the server. The WebNFS protocol reduces the number of over-the-wire
requests and makes traversing firewalls easier.
WebNFS offers no support for locking files across mounted filesystems. Hence, multiple clients
cannot synchronize their locking calls across WebNFS mounted filesystems.
30 Configuring and Administering NFS Services