cole@coledd.com
ftp://shadow.cabi.net/pub/Linux/BRCFG.tgz
/etc/lilo.conf
,
and re-run lilo
:
append = "ether=0,0,eth1"
If you have three interfaces on your bridge, use this line instead:
append = "ether=0,0,eth1 ether=0,0,eth2"
More interfaces can be found by adding more ether statements.
By default a stock Linux kernel probes for a single ethercard,
and once one is found the probe ceases.
The above append statement tells the kernel to keep probing
for more ethernet devices after the first one is found.
Alternatively, the boot parameter can be used instead:
linux ether=0,0,eth1
Or, with 3 interfaces, use:
linux ether=0,0,eth1 ether=0,0,eth2
BRIDGING
enabled.
/etc/sysconfig/network-scripts/
(for a RedHat system)
and copy ifcfg-lo0
to ifcfg-eth0
&
ifcfg-eth1
.
In these 2 eth files, change the line containing
``DEVICE=lo
'' to ``DEVICE=eth0
''
and ``DEVICE=eth1
''.
Other distributions may deviate from this, do what you need to do!
If there are more than 2 interfaces to this bridge,
be sure to make the corresponding configurations to those, as well.
ifconfig eth0 promisc ; ifconfig eth1 promisc
All interfaces which are connected to network segments to be bridged
are to be put into promiscuous mode.
brcfg
program:
brcfg -ena
tcpdump -i eth0 (in one window)
tcpdump -i eth1 (in another window)
tcpdump
on another machine
to verify the bridge is separating the segment correctly.
I get the message
ioctl(SIOCGIFBR) failed: Package not installed
What does this mean?
You don't have bridging capability in your kernel.
Get a 2.0 or greater kernel,
and recompile with the BRIDGING
option enabled.
Machines on one side cannot ping the other side!
brcfg -ena
''?
(brcfg
should say ``bridging is ENABLED
'')ifconfig
'' command.
The ``PROMISC
'' flag should be on for
both interfaces.)I cannot telnet
/ftp
from the bridge! Why?
This is because there is no IP address bound to any of bridge interfaces. A bridge is to be a transparent part of a network.
What do I need to set up in the way of routing?
Nothing!
All routing intelligence is handled by
the bridging code in the kernel.
To see the ethernet addresses as they are learned by the bridge,
use the brcfg
program in debug mode:
brcfg -deb
The bridge appears to work, but why doesn't ``traceroute'' show the bridge as a part of the path?
Due to the nature of a bridge, a ``traceroute'' should NOT show the bridge as a part of the path. A bridge is to be a transparent component of the network.
Is it necessary to compile IP_FORWARD
into the kernel?
No. The bridging code in the kernel takes care of the packet
transport.
IP_FORWARD
is for a gateway which has IP addresses
bound to its interfaces.
Why are the physical ethernet addresses for port 1 and port 2 the
same according to the ``brcfg
'' program?
Shouldn't they be different?
No. Every port on a bridge intentionally is assigned the same physical ethernet address by the bridging code.
Bridging does not appear to be an option when performing a make config on the kernel. How does one enable it?
During the kernel config, answer 'Y' to the question, ``Prompt for development and/or incomplete code/drivers (CONFIG_EXPERIMENTAL) [Y/n/?]''.
Too many hubs (4 or more) chained one after another (in series) cause timing problems on an ethernet. What effect does a bridge have in a subnet that is layered with hubs?
A bridge resets the 3/4/5 hubs rule. A bridge does not deal with packets the way a hub does, and is therefore not a contributor to timing problems on a network.
Can a bridge interface to both 10Mb and 100Mb ethernet segments? Will such a configuration slow down the rest of the traffic on the high speed side?
Yes, a bridge can tie together a 10Mb segment with a 100Mb segment. As long as the network card on the fast network is 100Mb capable, TCP takes care of the rest. While it's true that the packets from a host in the 100Mb network communicating to a host in the 10Mb network are moving at only 10Mb/s, the rest of the traffic on the fast ethernet is not slowed down.