The Internet Systems Consortium or commonly know as ISC has got its new look! ISC is very well-known from its very reliable free Open Source products like the DNS Server BIND and the ISC DHCP Server.
Its new website is super cool now and very well-organized than before thus making it easy for you to navigate and download the latest versions of their products. You can choose from their Current Release versions, Beta Release or Development Release versions and Maintenance Releases.
Saturday, November 15, 2008
FreeBSD 101: Creating a Bridge using FreeBSD
The reason why I came across with this application is that I want to sniff and examine packets lurking around the network. I could not use my switch since I only have an unmanageable switch so I cannot configure it to do port mirroring. I tried to look for hubs but could not find either. But I do have a machine that has multiple Network Interface Cards in it so I look for ways to configure these ports to broadcast frames/packets that it received from one port to all of the other ports so I can sniff any of the packets that enter in any of the ports.
I have done this before with the help of a friend but I cannot remember the exact details on how to do it. I'm not that type of guy who takes down notes for every new procedures/configurations I have done. So I spent some time googling around and finally found this link. I am going to summarize the procedures by posting a simple shell script that will create a bridge interface in FreeBSD.
Save this script at /usr/local/etc/rc.d so that it will get executed during boot-up process. Then make the script executable and execute it:
Just as there are many ways to kill a cat, there are also other ways to create a bridge interface in FreeBSD. One of which is to do it using rc.conf. But I think you still need to add "device if_bridge" into your kernel configuration /usr/src/sys/{arch}/conf/GENERIC so that it will be dynamically loaded by the kernel everytime you create a bridge interface.
I have done this before with the help of a friend but I cannot remember the exact details on how to do it. I'm not that type of guy who takes down notes for every new procedures/configurations I have done. So I spent some time googling around and finally found this link. I am going to summarize the procedures by posting a simple shell script that will create a bridge interface in FreeBSD.
#!/bin/sh
# Filename: createbridge.sh
# load the kernel loadable module
/sbin/kldload /boot/kernel/if_bridge.ko
# create a bridge interface
/sbin/ifconfig bridge0 create
# add the network interfaces you want as member of the bridge
/sbin/ifconfig bridge0 addm em0 addm em1 addm em2
# bring these interfaces up
/sbin/ifconfig em0 up
/sbin/ifconfig em1 up
/sbin/ifconfig em2 up
# then you can assign an ip address to your bridge interface if you want
/sbin/ifconfig bridge0 inet 192.168.1.1/24
Save this script at /usr/local/etc/rc.d so that it will get executed during boot-up process. Then make the script executable and execute it:
# chmod 755 /usr/local/etc/rc.d/createbridge.sh
# /usr/local/etc/rc.d/createbridge.sh
Just as there are many ways to kill a cat, there are also other ways to create a bridge interface in FreeBSD. One of which is to do it using rc.conf. But I think you still need to add "device if_bridge" into your kernel configuration /usr/src/sys/{arch}/conf/GENERIC so that it will be dynamically loaded by the kernel everytime you create a bridge interface.
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