Samba Domain Member Port Usage

Introduction

If you require to secure your Samba installation with a firewall, you would need information, what ports and protocols are used. This page will give you an overview.

Identify on which ports and interfaces Samba is listening

You can use "netstat" to identify which ports Samba and related daemons are listening on and on which IPs:

# netstat -tulpn | egrep "smbd|nmbd|winbind"

The following is a snippet of an example output:

tcp        0      0 127.0.0.1:139               0.0.0.0:*                   LISTEN      43270/smbd          
tcp        0      0 10.0.0.1:139                0.0.0.0:*                   LISTEN      43270/smbd          
tcp        0      0 127.0.0.1:445               0.0.0.0:*                   LISTEN      43270/smbd          
tcp        0      0 10.0.0.1:445                0.0.0.0:*                   LISTEN      43270/smbd          
.....

The above example shows, that the services are listening on localhost (127.0.0.1) and the interface with IP 10.0.0.1 - each on the listed ports (139, 445,...).

Port usage when Samba runs as a Member Server

Service	Port	protocol
End Point Mapper (DCE/RPC Locator Service)	135	tcp
NetBIOS Name Service	137	udp
NetBIOS Datagram	138	udp
NetBIOS Session	139	tcp
SMB over TCP	445	tcp

Prevent Samba from listening on all interfaces

Sometimes you don't want Samba to listen on all interfaces of your host. For example, when the host is directly connected to the internet, you surely don't want to provide your shares to the rest of the world. If you limit Samba to listen only on the internal NIC(s), you don't need a firewall to prevent access from the outside.

Add the following to the "[global]" section of your smb.conf to bind Samba to eth0 and loopback:

bind interfaces only = yes
interfaces = lo eth0

The "interfaces" parameter allows various ways to restrict. See the manpage for more details.

After the changes, restart Samba.