Port 20048 MOUNTD
Port 20048 is the IANA-assigned mountd port for NFS mount protocol (TCP / UDP).
What is port 20048 used for?
Port 20048 is assigned to mountd and uses TCP / UDP. The IANA registry describes the service as “NFS mount protocol”. It sits above the registered range, where most numbers are transient client ports. A fixed high port is worth documenting precisely because tooling often assumes the default.
Ports are the transport-layer address a service listens on. A client that wants to reach mountd connects to port 20048. A TCP connection is refused when nothing is listening, while a UDP request simply goes unanswered. That is why a port conflict appears whenever two processes try to bind the same number.
Use the commands below to confirm whether port 20048 is actually in use before you change firewall rules. Blocking the port stops new inbound traffic at the firewall, but it does not stop a local process from listening, and it does not remove the service from the machine.
Browse all File transfer and sharing ports
Source: IANA Service Name and Transport Protocol Port Number Registry. Registered assignee: [Nicolas_Williams].
Check and block port 20048
Copy-ready commands for the protocols assigned to this port. Run the check first, then block only what should not be reachable.
Check on Linux
sudo ss -tlpn 'sport = :20048'
sudo ss -ulpn 'sport = :20048'Check on Windows
Get-NetTCPConnection -LocalPort 20048 -State Listen -ErrorAction SilentlyContinue
Get-NetUDPEndpoint -LocalPort 20048 -ErrorAction SilentlyContinueBlock with UFW
sudo ufw deny 20048/tcp
sudo ufw deny 20048/udpBlock with iptables
sudo iptables -A INPUT -p tcp --dport 20048 -j DROP
sudo iptables -A INPUT -p udp --dport 20048 -j DROPThese commands are examples for a typical host. Check the listener before you change firewall rules, and persist iptables rules with iptables-save or netfilter-persistent. On Windows, use Windows Defender Firewall or New-NetFirewallRule for persistent blocks. The iptables rules here cover IPv4; mirror them with ip6tables if IPv6 is enabled.
Is port 20048 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Where port 20048 is usually used
Most traffic on port 20048 falls into these scenarios. The demo below is a safe way to confirm the listener before you change anything.
- Transferring build artifacts, backups or exports between trusted hosts.
- Mounting or browsing shared directories inside a private network.
- Scheduled sync jobs that connect on a fixed port.
Check the service
Probe the port before debugging credentials or share permissions.
nc -vz 127.0.0.1 20048Common problems with port 20048
Connection refused or timed out
Refused usually means the host is reachable but nothing is listening on port 20048. A timeout more often means a firewall drop, a wrong host or a service bound to a different interface.
Port already in use
Find the process holding the port with sudo ss -tlpn 'sport = :20048' or sudo lsof -i :20048. Stop that process or configure it to bind another port; killing it without identifying it can take down a production service.
Firewall rule did not survive a reboot
UFW and Windows Firewall keep rules across restarts. Raw iptables rules do not: save them with iptables-save or the netfilter-persistent package, and re-apply after upgrades that reset the ruleset.
The port is blocked but still reachable
A firewall rule filters inbound traffic; it does not close the listener. Confirm with the check command above and bind the service to 127.0.0.1 when only local clients need it.
Port 20048 at a glance
| Port number | 20048 |
|---|---|
| Service name | mountd |
| Transport protocol | TCP / UDP |
| Category | File transfer and sharing |
| Range | High port (10001–65535) |
| Risk level | Standard/Low |
| Registered assignee | [Nicolas_Williams] |
| Registry description | NFS mount protocol |
| Source | IANA Service Name and Transport Protocol Port Number Registry |
Frequently asked questions
What is port 20048 used for?
Port 20048 (MOUNTD) uses TCP / UDP. NFS mount protocol.
How do I check if port 20048 is open?
On Linux run `sudo ss -tlpn 'sport = :20048'` and `sudo ss -ulpn 'sport = :20048'`. On Windows run `Get-NetTCPConnection -LocalPort 20048 -State Listen -ErrorAction SilentlyContinue` and `Get-NetUDPEndpoint -LocalPort 20048 -ErrorAction SilentlyContinue` in PowerShell. If the port is open, the output shows a process listening on port 20048; empty output usually means nothing is bound to it.
How do I block port 20048?
With UFW run `sudo ufw deny 20048/tcp` and `sudo ufw deny 20048/udp`. With iptables run `sudo iptables -A INPUT -p tcp --dport 20048 -j DROP` and `sudo iptables -A INPUT -p udp --dport 20048 -j DROP`. Persist the iptables rules with your distribution's netfilter-persistent or iptables-save tooling so they survive a reboot.
Is port 20048 safe to expose?
This port is not on our curated list of services with a widely exploited profile. Exposure is only safe when the listening service is intended, patched and protected by a firewall. Nevertheless, keep the listening service patched and remove it if unused. A default-deny firewall policy with explicit allow rules is still the safest baseline.
Related ports
- Port 20046 · tmophl7mtsTMOP HL7 Message Transfer Service
- Port 20049 · nfsrdmaNetwork File System (NFS) over RDMA
- Port 7117 · rothagaEncrypted chat and file transfer service
- Port 5233 · enfsEtinnae Network File Service
- Port 22537 · caldsoft-backupCaldSoft Backup server file transfer
- Port 2257 · simple-tx-rxsimple text/file transfer
Primary data: IANA Service Name and Transport Protocol Port Number Registry.
Last reviewed 2026-10-30 · Methodology · About · Privacy