View source for Bridges with Linux

=Bridge Utilities in Linux=

==The bridge-utils package==

'''Installation''':

 $ sudo apt-get install bridge-utils

'''Commands''':

 $ dpkg -L bridge-utils | grep bin
 /usr/sbin
 '''/usr/sbin/brctl'''

'''Configuration files''':

 $ dpkg -L bridge-utils | grep etc
 /etc
 /etc/network
 /etc/network/if-pre-up.d
 /etc/network/if-pre-up.d/bridge
 /etc/network/if-post-down.d
 /etc/network/if-post-down.d/bridge

'''Resources''':

*[http://linux.die.net/man/8/brctl brctl]

===The bridge control command 'brctl'===

'''Show the bridges''':

 $ brctl show 
  bridge name     bridge id               STP enabled     interfaces
  br0             8000.001601a1a9b7       no              eth0
                                                          wlan0
  br1             8000.000000000000       no              

'''Create a new bridge''':

 $ brctl addbr br1

'''Add/delete interfaces a un bridge''':

 $ brctl delif

 $ brctl addif

===Creation of a bridge===

We install the package [[Bridges_with_Linux#The_bridge-utils_package | bridge-utils]] and the file '''/etc/network/interfaces'''. 
Then we create an interface as a bridge from eth0:

 $ cat /etc/network/interfaces
 
 auto lo
 iface lo inet loopback
 
 auto br0
 iface br0 inet static
  address 192.168.1.2
  netmask 255.255.255.0
  gateway 192.168.1.1
  '''bridge_ports eth0'''
 
 auto eth0
 '''iface eth0 inet manual'''

We can use DHCP, as well:

 $ cat /etc/network/interfaces
 
 auto lo
 iface lo inet loopback
 
 auto br0
 iface br0 inet dhcp
  '''bridge_ports eth0'''
 
 auto eth0
 '''iface eth0 inet manual'''

 '''NOTE''': Note how the interface eth0 is manually configured and the line '''bridge_ports eth0'''.


We restart to initialize the network:

 $ sudo /etc/init.d/networking restart

From now on the eth0 interface can be observed by executing '''ifconfig''':

 $ ifconfig
 br0       Link encap:Ethernet  HWaddr 00:30:1B:B7:CD:B6  
           inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
           inet6 addr: fe80::230:1bff:feb7:cdb6/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:28932 errors:0 dropped:0 overruns:0 frame:0
           TX packets:28277 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:0 
           RX bytes:24356075 (23.2 MB)  TX bytes:17213164 (16.4 MB)
 
 eth0      Link encap:Ethernet  HWaddr 00:30:1B:B7:CD:B6  
           inet6 addr: fe80::230:1bff:feb7:cdb6/64 Scope:Link
           UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
           RX packets:20788 errors:0 dropped:0 overruns:0 frame:0
           TX packets:14681 errors:0 dropped:0 overruns:0 carrier:0
           collisions:0 txqueuelen:1000 
           RX bytes:23664360 (22.5 MB)  TX bytes:1995733 (1.9 MB)
           Interrupt:20 



It is a non configured interface (Dummy). This is normal, check the network if it still works.

==The package uml-utilities==

Installation of User Mode Linux utilities package (uml-utilities):

 $ sudo apt-get install uml-utilities

The User Mode Linux package contains tools to create [https://en.wikipedia.org/wiki/Network_tap TAP] interfaces.
Add permissions to access the user interface:

 $ sudo gpasswd -a <user> uml-net

For example:

 $ sudo gpasswd -a sergi uml-net

We need to restart to apply the permissions. 

We edit the file '''/etc/network/interfaces''' To add the TAP interface by appending:

 auto tap0
 iface tap0 inet manual
      up ifconfig $IFACE 0.0.0.0 up
      down ifconfig $IFACE down
      tunctl_user <user>

We replace the placeholer ''<user>'' with out username. For example:

 auto tap0
 iface tap0 inet manual
      up ifconfig $IFACE 0.0.0.0 up
      down ifconfig $IFACE down
      tunctl_user sergi
      bridge_ports eth0 tap0

Restart to initialize the network:

 $ sudo /etc/init.d/networking restart

=The command tunctl=

Now we create a bridge:

 $ sudo tunctl -t tap1 -u sergi
 $ sudo chmod 666 /dev/net/tun

And:

 $ sudo brctl addbr br0 

 $ sudo ifconfig eth0 0.0.0.0 promisc 
 $ sudo brctl addif br0 eth0
 $ dhclient br0


 $ sudo brctl addif br0 tap1 

=Resources=

*[https://help.ubuntu.com/community/VirtualBox#head-ac88c03223e773c78dbb46b4b13c109de1143a03 Ubuntu VirtualBox]
*[http://gentoo-wiki.com/HOWTO_setup_a_gentoo_bridge HOWTO_setup_a_gentoo_bridge]

[[ca:Bridges amb Linux]]