SY0-301 · Question #351
Which of the following ports should be opened on a firewall to allow for NetBIOS communication? (Select TWO).
The correct answer is B. 137 C. 139. NetBIOS relies on specific UDP and TCP ports for name resolution and session services. Ports 137 and 139 must be opened to allow NetBIOS traffic through a firewall.
Question
Which of the following ports should be opened on a firewall to allow for NetBIOS communication? (Select TWO).
Options
- A110
- B137
- C139
- D143
- E161
- F443
How the community answered
(45 responses)- A2% (1)
- B91% (41)
- D2% (1)
- E4% (2)
Why each option
NetBIOS relies on specific UDP and TCP ports for name resolution and session services. Ports 137 and 139 must be opened to allow NetBIOS traffic through a firewall.
Port 110 is assigned to POP3 (Post Office Protocol v3) for email retrieval, not NetBIOS.
Port 137 is used by the NetBIOS Name Service (NBNS), which handles name registration and resolution - the equivalent of DNS for NetBIOS networks. Without this port, NetBIOS devices cannot resolve hostnames to IP addresses.
Port 139 is used by the NetBIOS Session Service, which establishes and manages connections between NetBIOS-enabled hosts for file and printer sharing over TCP.
Port 143 is assigned to IMAP (Internet Message Access Protocol) for email access, not NetBIOS.
Port 161 is assigned to SNMP (Simple Network Management Protocol) for device monitoring, not NetBIOS.
Port 443 is assigned to HTTPS for encrypted web traffic, not NetBIOS.
Concept tested: NetBIOS firewall port requirements
Source: https://learn.microsoft.com/en-us/troubleshoot/windows-server/networking/service-overview-and-network-port-requirements
Topics
Community Discussion
No community discussion yet for this question.