Mounting NFS-server running in VM: Connection timed out

Question

I have stumbled upon this general problem with NFS in virtualized machines it seems. Long story short, I tried to roll up a FOG-server, that uses NFS.

• The NFS-server VM-host is in bridged mode with IP: 10.0.0.136
• can mount the NFS-share from other VMs on the physical host, but not from other LAN-devices.
• The virtual machine is in NAT Bridge-mode no matter what VM-platform I use.
• Firewall disabled - ports.. are.. open..
• The physical machine running the VM-platform is a Windows 10 Home, disabled firewall and Intel-network adapter.

The problem: When I mount from other LAN-devices I get 'Connection timed out', but showmount responds after 2 min and 10 sec. This test is performed from a Synology-NAS on the same LAN-network.

# mount -v -t nfs nfsserver:/images /volume1/test
mount.nfs: timeout set for Tue Jan 30 23:43:55 2018
mount.nfs: trying text-based options 'vers=3,tcp,soft,nolock,addr=10.0.0.136'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 10.0.0.136 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=6
mount.nfs: trying 10.0.0.136 prog 100005 vers 3 prot TCP port 56755
mount.nfs: mount(2): Connection timed out
mount.nfs: trying text-based options 'vers=3,tcp,soft,nolock,addr=10.0.0.136'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 10.0.0.136 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=6
mount.nfs: trying 10.0.0.136 prog 100005 vers 3 prot TCP port 56755
mount.nfs: mount(2): Connection timed out
mount.nfs: trying text-based options 'vers=3,tcp,soft,nolock,addr=10.0.0.136'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 10.0.0.136 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=6
mount.nfs: trying 10.0.0.136 prog 100005 vers 3 prot TCP port 56755

# showmount -e nfsserver
Export list for 10.0.0.136:
/images/dev 10.0.0.0/24
/images     10.0.0.0/24

It works as intended, when I mount from another VM-host on the same VMplatform - in this case Debian 9/VirtualBox: Instant mount and instant 'showmount -e'-response.

# mount -vt nfs nfsserver:/images /mnt/test
mount.nfs: timeout set for Wed Jan 31 01:03:30 2018
mount.nfs: trying text-based options 'vers=4.2,addr=10.0.0.136,clientaddr=10.0.0.108'
mount.nfs: mount(2): No such file or directory
mount.nfs: trying text-based options 'addr=10.0.0.136'
mount.nfs: prog 100003, trying vers=3, prot=6
mount.nfs: trying 10.0.0.136 prog 100003 vers 3 prot TCP port 2049
mount.nfs: prog 100005, trying vers=3, prot=17
mount.nfs: trying 10.0.0.136 prog 100005 vers 3 prot UDP port 33485

This is my /etc/exports on the nfsserver:

# cat /etc/exports
/images 10.0.0.0/24(ro,sync,no_wdelay,no_subtree_check,insecure_locks,no_root_squash,insecure,fsid=0)
/images/dev 10.0.0.0/24(rw,async,no_wdelay,no_subtree_check,no_root_squash,insecure,fsid=1)

This is the firewall (disabled):

# iptables -L
Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

The services are listening:

# rpcinfo -p
   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
    100005    1   udp  48327  mountd
    100005    1   tcp  47113  mountd
    100005    2   udp  50106  mountd
    100005    2   tcp  46029  mountd
    100005    3   udp  38832  mountd
    100005    3   tcp  46131  mountd
    100003    2   tcp   2049  nfs
    100003    3   tcp   2049  nfs
    100003    4   tcp   2049  nfs
    100227    2   tcp   2049
    100227    3   tcp   2049
    100003    2   udp   2049  nfs
    100003    3   udp   2049  nfs
    100003    4   udp   2049  nfs
    100227    2   udp   2049
    100227    3   udp   2049
    100021    1   udp  36259  nlockmgr
    100021    3   udp  36259  nlockmgr
    100021    4   udp  36259  nlockmgr
    100021    1   tcp  45767  nlockmgr
    100021    3   tcp  45767  nlockmgr
    100021    4   tcp  45767  nlockmgr

A portscan from a LAN-device timing out, shows open ports:

# nmap -p 111,2049 -T4 -A nfsserver
Starting Nmap 7.40 ( https://nmap.org ) at 2018-01-31 00:22 CET
Nmap scan report for nfsserver (10.0.0.136)
Host is up (0.00079s latency).
rDNS record for 10.0.0.136: nfsserver
PORT     STATE SERVICE VERSION
111/tcp  open  rpcbind 2-4 (RPC #100000)
| rpcinfo:
|   program version   port/proto  service
|   100000  2,3,4        111/tcp  rpcbind
|   100000  2,3,4        111/udp  rpcbind
|   100003  2,3,4       2049/tcp  nfs
|   100003  2,3,4       2049/udp  nfs
|   100005  1,2,3      38832/udp  mountd
|   100005  1,2,3      46131/tcp  mountd
|   100021  1,3,4      36259/udp  nlockmgr
|   100021  1,3,4      45767/tcp  nlockmgr
|   100227  2,3         2049/tcp  nfs_acl
|_  100227  2,3         2049/udp  nfs_acl
2049/tcp open  nfs_acl 2-3 (RPC #100227)
Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 6.33 seconds

/etc/hosts.allow and /etc/hosts.deny are both empty:

# cat /etc/hosts.allow /etc/hosts.deny
#

So far I've replicated the problem on:

• RHEL 7 / VirtualBox
• Debian 9 / VirtualBox
• Fedora 13 / VirtualBox
• Debian 9 / VMWare Workstation Player 14
• Ubuntu 16 / VMWare Workstation Player 14

It's strange! After trying this for almost a week, I surrender to you, mighty Gods of Serverfault

I'm clueless and humble!

How do I mount to an NFS-server running in a virtual machine without timing out?

Edit: Thanks for the formating. I tried tcpdumping both ends, and it seems some packets never arrive at the NFS-server inside the VM. It looks like a network issue deep inside virtualbox. Still clueless though..

Solution

I have no clue why this problem happens in VMs, but if I mount with version 3 it works.

mount -t nfs -o vers=3,nolock,proto=tcp nfsserver:/images /volume1/test

Solution found, but not really explainable..?