5355 LLMNRLink-Local Multicast Name Resolution.
Windows fallback name resolution. Disable it — LLMNR poisoning is a common credential-theft attack.
| Transport | Status | Meaning |
|---|---|---|
| TCP | Yes | Assigned by IANA and standardized, specified, or widely used on this port. |
| UDP | Yes | Assigned by IANA and standardized, specified, or widely used on this port. |
| SCTP | — | Not applicable for this transport. |
| DCCP | — | Not applicable for this transport. |
Registered (1024–49151). Assigned by IANA on request; usable without elevated privileges on most systems.
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Copy-ready inbound rules for the active transports. Replace every <source> placeholder with the specific host, subnet, or CIDR that should reach this port.
sudo ufw allow proto tcp from <source> to any port 5355Allow TCP 5355 (LLMNR). Replace <source> with the network/host that should reach it.
sudo ufw allow proto udp from <source> to any port 5355Allow UDP 5355 (LLMNR). Replace <source> with the network/host that should reach it.
sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="5355" protocol="tcp" accept'Allow TCP 5355 (LLMNR) from <source>. Run 'firewall-cmd --reload' afterwards.
sudo firewall-cmd --permanent --add-rich-rule='rule family="ipv4" source address="<source>" port port="5355" protocol="udp" accept'Allow UDP 5355 (LLMNR) from <source>. Run 'firewall-cmd --reload' afterwards.
nft add rule inet filter input ip saddr <source> tcp dport 5355 acceptAllow TCP 5355 (LLMNR). Assumes table 'inet filter' with an 'input' chain.
nft add rule inet filter input ip saddr <source> udp dport 5355 acceptAllow UDP 5355 (LLMNR). Assumes table 'inet filter' with an 'input' chain.
sudo iptables -A INPUT -p tcp -s <source> --dport 5355 -j ACCEPTAllow TCP 5355 (LLMNR). Persist with iptables-save/netfilter-persistent.
sudo iptables -A INPUT -p udp -s <source> --dport 5355 -j ACCEPTAllow UDP 5355 (LLMNR). Persist with iptables-save/netfilter-persistent.
az network nsg rule create -g <resource-group> --nsg-name <nsg> -n Allow-llmnr-5355 --priority 1000 --access Allow --direction Inbound --protocol "*" --source-address-prefixes <source> --destination-port-ranges 5355Inbound rule for 5355 (LLMNR). Set <source> to a CIDR; lower priority number = higher precedence.
aws ec2 authorize-security-group-ingress --group-id <sg-id> --ip-permissions IpProtocol=tcp,FromPort=5355,ToPort=5355,IpRanges="[{CidrIp=<source-cidr>}]"Inbound TCP 5355 (LLMNR). Replace <source-cidr> (e.g. 10.0.0.0/16).
aws ec2 authorize-security-group-ingress --group-id <sg-id> --ip-permissions IpProtocol=udp,FromPort=5355,ToPort=5355,IpRanges="[{CidrIp=<source-cidr>}]"Inbound UDP 5355 (LLMNR). Replace <source-cidr> (e.g. 10.0.0.0/16).
gcloud compute firewall-rules create allow-llmnr-5355 --direction=INGRESS --action=ALLOW --rules=tcp:5355,udp:5355 --source-ranges=<source-cidr> --network=<network>Ingress rule for 5355 (LLMNR). Scope with --source-ranges and optionally --target-tags.
netsh advfirewall firewall add rule name="Allow LLMNR 5355/TCP" dir=in action=allow protocol=TCP localport=5355 remoteip=<source>Inbound TCP 5355 (LLMNR). Set remoteip to a host/subnet; 'any' is discouraged.
netsh advfirewall firewall add rule name="Allow LLMNR 5355/UDP" dir=in action=allow protocol=UDP localport=5355 remoteip=<source>Inbound UDP 5355 (LLMNR). Set remoteip to a host/subnet; 'any' is discouraged.
New-NetFirewallRule -DisplayName "Allow LLMNR 5355/TCP" -Direction Inbound -Action Allow -Protocol TCP -LocalPort 5355 -RemoteAddress <source>Inbound TCP 5355 (LLMNR). Replace <source> with a host or subnet.
New-NetFirewallRule -DisplayName "Allow LLMNR 5355/UDP" -Direction Inbound -Action Allow -Protocol UDP -LocalPort 5355 -RemoteAddress <source>Inbound UDP 5355 (LLMNR). Replace <source> with a host or subnet.
Rules are generated only for transports marked active for this port. They default to an inbound allow with an explicit source placeholder — never any. Review direction, scope, and rule precedence before applying in production.