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Port 2042 (isis)

IANA assigns port 2042 to isis.

Registered (user) port, 1024-49151 TCPUDP

IANA assignment

Service nameProtoDescriptionAssigneeReference
isis TCP isis - -
isis UDP isis - -

Check what is listening on port 2042

Linux: is anything listening on TCP 2042?
sudo ss -tlnp 'sport = :2042'
Linux: UDP 2042
sudo ss -ulnp 'sport = :2042'
Linux / macOS: which process owns the port
sudo lsof -nP -i :2042
Older Linux / BSD (net-tools)
sudo netstat -tlnp | grep ':2042 '
Windows (Command Prompt)
netstat -ano | findstr :2042
Windows (PowerShell)
Get-NetTCPConnection -LocalPort 2042 -State Listen | Select LocalAddress,OwningProcess

Test it from outside

From another machine
nc -vz -w 5 HOST 2042
From Windows
Test-NetConnection HOST -Port 2042
UDP probe (no reply does not prove it is closed)
nc -vzu -w 5 HOST 2042

Block port 2042 in the firewall

ufw
sudo ufw deny 2042/tcp
iptables
sudo iptables -A INPUT -p tcp --dport 2042 -j DROP
nftables
sudo nft add rule inet filter input tcp dport 2042 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block TCP 2042' -Direction Inbound -Protocol TCP -LocalPort 2042 -Action Block
ufw
sudo ufw deny 2042/udp
iptables
sudo iptables -A INPUT -p udp --dport 2042 -j DROP
nftables
sudo nft add rule inet filter input udp dport 2042 drop
Windows Firewall
New-NetFirewallRule -DisplayName 'Block UDP 2042' -Direction Inbound -Protocol UDP -LocalPort 2042 -Action Block

Related ports

2037applus2039prizma2043isis-bcast2049NFS

All port numbers · Open port checker
Assignment data: IANA port number registry (public domain), retrieved 2026-11-10.