nfsd can't listen on udp

[Ksh J. Fry]

Hi, I'm running nfsd on FreeBSD (7.2 and 8.0) but it seem don't listen
on udp.

$ tail /etc/rc.conf
rpcbind_enable="YES"
rpc_lockd_enable="YES"
rpc_statd_enable="YES"
nfs_server_enable="YES"
nfs_server_flags="-t -u -n 4"
mountd_flags="-p 962 -r"


$ netstat -a -f inet | grep nfsd
tcp4       0      0 *.nfsd                 *.*                    LISTEN
udp4       0      0 *.nfsd                 *.*                   



$ sockstat -4 | grep nfsd
root     nfsd       44932 3  tcp4   *:2049                *:*
(no udp)

When I try to mount with mount_nfs -U and write something the client hang.

Thanks by advance.