On a fresh install of CentOS 6.9 with all updates, i can mount NFS with UDP protocol and run `rpcinfo -u 10.3.255.234 nfs 3`, the answer is "program 100003 version 3 ready and waiting". I can mount any NFS export over UDP without any problem.
However, when it comes to TCP, any mount attempt hangs 3 min then times out. Same for `rpcinfo -t 10.3.255.234 nfs 3`. I have several other servers with CentOS 6.9 with all udpates, they can mount NFS over TCP without any problem, and run rpcinfo -t and -u, they get positive answers. They are not fresh install.
I can observe the following behaviors on the faulty clients:
1. no layer 4 protocol option: we see that even the UDP attempt times out
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[root@srv-tls-test02 ~]# mount -t nfs 10.3.255.234:/vol/vol_testunix /mnt -o vers=3 -v
mount.nfs: timeout set for Thu Jan 18 10:48:40 2018
mount.nfs: trying text-based options 'vers=3,addr=10.3.255.234'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 10.3.255.234 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 10.3.255.234 prog 100005 vers 3 prot UDP port 4046
(timeout)
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[root@srv-tls-test02 ~]# mount -t nfs 10.3.255.234:/vol/vol_testunix /mnt -o vers=3,tcp -v
mount.nfs: timeout set for Thu Jan 18 10:49:25 2018
mount.nfs: trying text-based options 'vers=3,tcp,addr=10.3.255.234'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 10.3.255.234 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=6
mount.nfs: trying 10.3.255.234 prog 100005 vers 3 prot TCP port 4046
(timeout)
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[root@srv-tls-test02 ~]# mount -t nfs 10.3.255.234:/vol/vol_testunix /mnt -o vers=3,udp -v
mount.nfs: timeout set for Thu Jan 18 10:49:49 2018
mount.nfs: trying text-based options 'vers=3,udp,addr=10.3.255.234'
mount.nfs: prog 100003, trying vers=3, prot=17
mount.nfs: trying 10.3.255.234 prog 100003 vers 3 prot UDP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 10.3.255.234 prog 100005 vers 3 prot UDP port 4046
10.3.255.234:/vol/vol_testunix on /mnt type nfs (rw,vers=3,udp)
I tried fresh install CentOS 6.9 on 2 different servers with different hardware, both time out with NFS over TCP.
This is not a permission problem. If I spoof the faulty IP with a working server, I can mount over TCP without any problem.
The NFS server is a NetApp filer, so I don't have full control on it. If I nmap it from non-working server, i see NFS and rpcbind ports open.
I suspect the default configuration on client side. iptables and ip6tables are flushed and disabled. IPv6 is not used at all. rpcbind, portmapper, mountd, lockd, statd, nfs services are running. rpcinfo on localhost displays "portmapper", "status" and "mountd" for both tcp and udp.
rpcinfo -p localhost:
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[root@srv-tls-test02 ~]# rpcinfo -p localhost
program vers proto port service
100000 4 tcp 111 portmapper
100000 3 tcp 111 portmapper
100000 2 tcp 111 portmapper
100000 4 udp 111 portmapper
100000 3 udp 111 portmapper
100000 2 udp 111 portmapper
100024 1 udp 34749 status
100024 1 tcp 57346 status
100005 1 udp 51983 mountd
100005 1 tcp 34221 mountd
100005 2 udp 51130 mountd
100005 2 tcp 49610 mountd
100005 3 udp 60273 mountd
100005 3 tcp 55271 mountd
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[root@srv-tls-test02 ~]# ps aux | egrep "nfs|rpc|lock"
root 28 0.0 0.0 0 0 ? S 10:04 0:00 [kblockd/0]
root 29 0.0 0.0 0 0 ? S 10:04 0:00 [kblockd/1]
rpcuser 1380 0.0 0.0 23352 1368 ? Ss 10:04 0:00 rpc.statd
root 1468 0.0 0.0 0 0 ? S 10:04 0:00 [rpciod/0]
root 1469 0.0 0.0 0 0 ? S 10:04 0:00 [rpciod/1]
root 1683 0.0 0.0 0 0 ? S 10:07 0:00 [nfsiod]
root 1919 0.0 0.0 21672 992 ? Ss 10:21 0:00 rpc.mountd
root 1925 0.0 0.0 0 0 ? S 10:21 0:00 [lockd]
root 1926 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd4]
root 1927 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd4_callbacks]
root 1928 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1929 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1930 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1931 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1932 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1933 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1934 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1935 0.0 0.0 0 0 ? S 10:21 0:00 [nfsd]
root 1966 0.0 0.0 25172 632 ? Ss 10:21 0:00 rpc.idmapd
rpc 2021 0.0 0.0 18980 932 ? Ss 10:22 0:00 rpcbind
rpcuser 2042 0.0 0.0 23352 1364 ? Ss 10:39 0:00 rpc.statd --no-notify
root 2225 0.0 0.0 21672 996 ? Ss 11:15 0:00 rpc.mountd
root 2239 0.0 0.0 103324 900 pts/1 S+ 11:25 0:00 egrep nfs|rpc|lock
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[root@srv-tls-test02 ~]# uname -a
Linux srv-tls-test02 2.6.32-696.18.7.el6.x86_64 #1 SMP Thu Jan 4 17:31:22 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux
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[root@srv-tls-test02 ~]# cat /etc/redhat-release
CentOS release 6.9 (Final)
EDIT: added information about running services.
EDIT2: added sysinfo