iptables: Samba

Ports that Samba uses Samba uses NetBIOS ports 137,138 udp and 139 tcp. It also uses port 445 for SMB file sharing without NetBIOS. Sample iptables rules for Samba: SAMBA_SERVER=”″ […]

iptables Linux

iptables stop people who make too many connections in a time period

Well it’s a simple deal but iptables can count the number of connections in a time period and block based on it.  For example:


iptables log before you drop with a tag

It’s always a good thing to log anything you drop this allows you to troubleshoot issues later.   In iptables this is very easy.  If you place your drop at the […]

iptables Linux

Block outgoing smtp except to an approved relay in iptables

Just like most sysadmins I have to deal with developers who want to zip off a quick email after their application finishes processing, sounds good right?  Yes it is… but […]

iptables Linux Oracle

Oracle 11gR2 Rac GNS iptables

Well here goes another Oracle 11gR2 note for you all out there.  Let me just say Oracle’s documentation either does not exist or is so buried it’s impossible to find […]

iptables Linux

Test TCP and UDP connections in Linux for firewalls

I am constantly having to check firewall rules for sevices I have not yet setup.  In this post I will reference the client (Source address) and server (Destination address). Checking […]

iptables Linux

iptables Block all outgoing traffic

What is the use of blocking out going traffic?  Imagine if you have a web server and you want to allow customers to access your webserver but you do not […]

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