Port 111 rpcbind / portmapper · TCP and UDP

What runs on port 111

rpcbind (portmapper): the directory service for ONC RPC programs, chiefly NFS. A client asks rpcbind on 111 which port mountd, nlockmgr and the rest are using. NFSv4 does not need it (everything is on 2049), but NFSv3 setups do. Exposed to the internet it is both an information leak and an amplification vector.

Software that uses it: rpcbind · NFS servers (nfs-utils) · NIS

Should port 111 be open?

Private network or VPN only. Nothing good comes from this port being reachable from the internet. Keep it on an internal network, reach it over a VPN or an SSH tunnel, and firewall it from everything that does not need it.

• rpcinfo -p host lists everything registered; if that works from the internet, fix the firewall.
• Pin mountd and statd to fixed ports so you can firewall NFSv3 properly.

Check port 111

# on the host: is anything listening, and which process?
ss -ltnp 'sport = :111'
ss -lunp 'sport = :111'
sudo lsof -i :111

# from another machine: is it reachable?
nc -zv host 111
nmap -p 111 host
nc -zuv host 111
sudo nmap -sU -p 111 host
curl -v telnet://host:111      # raw TCP connect test, Ctrl-C to leave

A port that answers from the internet when it should not is the finding; nmap from a machine outside your network (or a VPS) is the honest test, because scans from inside the LAN pass the firewall you are trying to verify.

Allow or block port 111

# ufw (Ubuntu/Debian)
sudo ufw allow from 10.0.0.0/8 to any port 111 proto tcp
sudo ufw allow from 10.0.0.0/8 to any port 111 proto udp
sudo ufw deny 111/tcp
sudo ufw deny 111/udp

# nftables
nft add rule inet filter input ip saddr 10.0.0.0/8 meta l4proto { tcp, udp } th dport 111 accept
nft add rule inet filter input meta l4proto { tcp, udp } th dport 111 drop

# iptables (legacy)
iptables -A INPUT -p tcp --dport 111 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p tcp --dport 111 -j DROP
iptables -A INPUT -p udp --dport 111 -s 10.0.0.0/8 -j ACCEPT
iptables -A INPUT -p udp --dport 111 -j DROP

# firewalld
sudo firewall-cmd --permanent --add-rich-rule='rule family=ipv4 source address=10.0.0.0/8 port port=111 protocol=tcp accept'

Replace 10.0.0.0/8 with the networks that need access. Allowing by source address is the rule that matters; "allow 111" with no source is just "open".

Related ports

• 2049 NFS — Network file system
• 445 SMB — Windows file sharing, Samba

Part of the port number reference. Ports are 16-bit numbers; see also the subnet calculator and the packet decoder, which shows ports inside TCP and UDP headers.

Questions