Linux Iptables Allow NFS Clients to Access the NFS Server

The portmapper assigns each NFS service to a port dynamically at service startup time. How do I allow legitimate NFS clients to access the NFS server using RHEL / Fedora / CentOS Linux 5.x iptables firewall?

You need to open the following ports:
a] TCP/UDP 111 – RPC 4.0 portmapper

b] TCP/UDP 2049 – NFSD (nfs server)

c] Portmap static ports – Various TCP/UDP ports defined in /etc/sysconfig/nfs file.

Configure NFS Services to Use Fixed Ports

However, NFS and portmap are pretty complex protocols. Firewalling should be done at each host and at the border firewalls to protect the NFS daemons from remote
access, since NFS servers should never be accessible from outside the organization. However, by default, the portmapper assigns each NFS service to a port dynamically at service startup time.

Dynamic ports cannot be protected by port filtering firewalls such as iptables. First, you need to configure NFS services to use fixed ports. Open /etc/sysconfig/nfs, enter:
# vi /etc/sysconfig/nfs
Modify config directive as follows to set TCP/UDP unused ports:

# TCP port rpc.lockd should listen on.
LOCKD_TCPPORT=lockd-port-number
# UDP port rpc.lockd should listen on.
LOCKD_UDPPORT=lockd-port-number 
# Port rpc.mountd should listen on.
MOUNTD_PORT=mountd-port-number
# Port rquotad should listen on.
RQUOTAD_PORT=rquotad-port-number
# Port rpc.statd should listen on.
STATD_PORT=statd-port-number
# Outgoing port statd should used. The default is port is random
STATD_OUTGOING_PORT=statd-outgoing-port-number

# TCP port rpc.lockd should listen on.
LOCKD_TCPPORT=lockd-port-number
# UDP port rpc.lockd should listen on.
LOCKD_UDPPORT=lockd-port-number
# Port rpc.mountd should listen on.
MOUNTD_PORT=mountd-port-number
# Port rquotad should listen on.
RQUOTAD_PORT=rquotad-port-number
# Port rpc.statd should listen on.
STATD_PORT=statd-port-number
# Outgoing port statd should used. The default is port is random
STATD_OUTGOING_PORT=statd-outgoing-port-number

Here is sample listing from one of my production NFS server:

LOCKD_TCPPORT=32803
LOCKD_UDPPORT=32769
MOUNTD_PORT=892
RQUOTAD_PORT=875
STATD_PORT=662
STATD_OUTGOING_PORT=2020

LOCKD_TCPPORT=32803
LOCKD_UDPPORT=32769
MOUNTD_PORT=892
RQUOTAD_PORT=875
STATD_PORT=662
STATD_OUTGOING_PORT=2020

Save and close the files. Restart NFS and portmap services:
# service portmap restart
# service nfs restart
# service rpcsvcgssd restart

Update /etc/sysconfig/iptables files

Open /etc/sysconfig/iptables, enter:
# vi /etc/sysconfig/iptables
Add the following lines, ensuring that they appear before the final LOG and DROP lines for the RH-Firewall-1-INPUT chain:

-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p udp --dport 111 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 111 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p tcp --dport 2049 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24  -m state --state NEW -p tcp --dport 32803 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24  -m state --state NEW -p udp --dport 32769 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24  -m state --state NEW -p tcp --dport 892 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24  -m state --state NEW -p udp --dport 892 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24  -m state --state NEW -p tcp --dport 875 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24  -m state --state NEW -p udp --dport 875 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24  -m state --state NEW -p tcp --dport 662 -j ACCEPT
-A RH-Firewall-1-INPUT -s 192.168.1.0/24 -m state --state NEW -p udp --dport 662 -j ACCEP

Save and close the file. Replace 192.168.1.0/24 with your actual LAN subnet /mask combo. You need to use static port values defined by /etc/sysconfig/nfs config file. Restart iptables service:
# service iptables restart

This entry is 6 of 15 in the Linux / UNIX NFS File Server Tutorial series. Keep reading the rest of the series:

  1. CentOS / Redhat: Setup NFS v4.0 File Server
  2. Debian / Ubuntu Linux: Setup NFSv4 File Server
  3. Mac Os X: Mount NFS Share / Set an NFS Client
  4. RHEL: How Do I Start and Stop NFS Service?
  5. How To Restart Linux NFS Server Properly When Network Become Unavailable
  6. Linux Iptables Allow NFS Clients to Access the NFS Server
  7. Debian / Ubuntu Linux Disable / Remove All NFS Services
  8. Linux: Tune NFS Performance
  9. Mount NFS file system over a slow and busy network
  10. Linux Track NFS Directory / Disk I/O Stats
  11. Linux Disable / Remove All NFS Services
  12. Linux: NFS4 mount Error reason given by server: No such file or directory
  13. Linux NFS Mount: wrong fs type, bad option, bad superblock on fs2:/data3 Error And Solution
  14. CentOS / RHEL CacheFS: Speed Up Network File System (NFS) File Access
  15. Increase NFS Client Mount Point Security

Posted by: SXI ADMIN

The author is the creator of SXI LLC and a seasoned sysadmin, DevOps engineer, and a trainer for the Linux operating system/Unix shell scripting. Get the latest tutorials on SysAdmin, Linux/Unix and open source topics via RSS/XML feed or weekly email newsletter.