Re: [NFS] nfs-over-tcp still needs udp ports? (SLES 11)

[Tom Talpey <tmtalpey@gmail.com>]

At 11:26 AM 5/7/2009, Frank Steiner wrote:
>Leonardo Chiquitto wrote
>
>>> Is there a way to prevent those UDP connects?
>> 
>> Yes, add "mountproto=tcp" to your mount options.
>
>I was only aware of "proto=tcp" and indeed missed the mountproto option.
>
>Thanks both Leonardo and Trond for your answers!
>

There is one small caveat to using mountproto=tcp through firewalls:
while the mount will succeed, there are some side protocol exchanges
which may not.

In particular, if you do NLM file locking, there is a server callback (NLM
"granted") which the server may choose to issue via UDP. If this callback
is not seen by the client due to firewall blocking, there may be a 30-second
pause before a client retry unblocks the caller.

Also, the NSM (status monitor) exchanges are often performed via UDP.
Again, if you are using NLM and the server reboots, the client may not
become aware of this promptly, and lock reclaim will be affected.

OTOH, if your applications don't use locking on the NFS mounts, you'll
probably be fine.

Tom.


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