FreeBSD Filtering Bridge to block NETBIOS over TCP Traffic

Posted on 2005-04-26
Last Modified: 2013-11-22
I already have a functional FreeBSD 5.3 Bridge with an open firewall (ipfw) enabled.

What rules need to go in the /etc/rc.firewall.local file to allow everything through (both ways) except for NETBIOS traffic.

Do I put in "add all from any to any" at the bottom and work my way up from thier?
Question by:tuaris
    LVL 1

    Author Comment

    Also, how do I make "tcpdump" startup automaticly on boot and display on screen without logging in as anyone?
    LVL 3

    Accepted Solution

    ipfw add 1000 deny tcp from any to any 135-139
    ipfw add 2000 deny udp from any to any 135-139
    ipfw add 60000 allow ip from any to any

    >>>Also, how do I make "tcpdump" startup automaticly on boot and display on screen without logging in as anyone?

    It is NOT recommended! If you need to view trafic you can use trafshow, most lukely.
    Although you can try the following:
    put the line
    /usr/sbin/tcpdump -i rl0 > /dev/console
    in /etc/rc.local, if it not exist create it. After reboot it will do this. rl0 - is the interface which you need.

    LVL 1

    Author Comment

    How come it's not recomended to have tcpdumd start automaticly?
    LVL 3

    Expert Comment

    Depending on your version of Unix and it's configuration tcpdump put the interface in promiscuous mode and runned under super-user mode which is unsecured. In most versions of Unix, like IRIX, HP-UX, Solaris it must be installed and runed by root :(. For BSD you must have super-user read permisions on  /dev/bpf* (avialable for Mac-OS too).
    LVL 61

    Assisted Solution


    > Also, how do I make "tcpdump" startup automaticly on boot and display on screen without logging in as anyone?
    add it to /etc/ttys ( not good )
    LVL 1

    Author Comment

    Works great thank you both.

    Write Comment

    Please enter a first name

    Please enter a last name

    We will never share this with anyone.

    Featured Post

    How to run any project with ease

    Manage projects of all sizes how you want. Great for personal to-do lists, project milestones, team priorities and launch plans.
    - Combine task lists, docs, spreadsheets, and chat in one
    - View and edit from mobile/offline
    - Cut down on emails

    My previous tech tip, Installing the Solaris OS From the Flash Archive On a Tape (, discussed installing the Solaris Operating S…
    About FreeBSD Jails In FreeBSD, jails are a way of doing operating system level virtualization.  The basis of FreeBSD jails is chroot (, which changes the root directory of processes.  As a…
    Learn how to navigate the file tree with the shell. Use pwd to print the current working directory: Use ls to list a directory's contents: Use cd to change to a new directory: Use wildcards instead of typing out long directory names: Use ../ to move…
    This video shows how to set up a shell script to accept a positional parameter when called, pass that to a SQL script, accept the output from the statement back and then manipulate it in the Shell.

    779 members asked questions and received personalized solutions in the past 7 days.

    Join the community of 500,000 technology professionals and ask your questions.

    Join & Ask a Question

    Need Help in Real-Time?

    Connect with top rated Experts

    13 Experts available now in Live!

    Get 1:1 Help Now