How do you bridge one ethernet and not the other?

I have a Linux computer that sits in my living room and speaks over a
wireless network with WPA using wpa_supplicant. That works fine. This
computer also has an ethernet card in it. I'd like to connect another
device into that ethernet with a crossover cable and let that other
device use DHCP to get an address from my DHCP server (which is on the
other side of the wireless network). Do I set that ethernet card up as a
bridge? If so, how?

Scott Simpson <(E-Mail Removed)> wrote:
> I have a Linux computer that sits in my living room and speaks over a
> wireless network with WPA using wpa_supplicant. That works fine. This
> computer also has an ethernet card in it. I'd like to connect another
> device into that ethernet with a crossover cable and let that other
> device use DHCP to get an address from my DHCP server (which is on the
> other side of the wireless network). Do I set that ethernet card up as a
> bridge? If so, how?

It can be tricky to bridge a wireless device. An alternative option is
to use proxy arp. See http://tldp.org/HOWTO/Proxy-ARP-Subnet/why.html

Chris

Hello,

Chris Davies a écrit :
>
> It can be tricky to bridge a wireless device. An alternative option is
> to use proxy arp. See http://tldp.org/HOWTO/Proxy-ARP-Subnet/why.html

<quote>
Unfortunately, the wireless Ethernet interface cannot be put into
"Promiscuous" mode. This is mainly due to the lower bandwidth of the
wireless Ethernet (2MBit/sec) meaning that we don't want to carry any
traffic not specifically destined to another wireless Ethernet machine
or broadcasts.
<end of quote>

Huh ? What does promiscuous mode have to do with the supposedly lower
bandwidth ? Sending traffic takes bandwidth, receiving doesn't. The
explanation found in the Linux-net wiki seems more credible to me.

<http://www.linux-foundation.org/en/Net:Bridge#It_doesn.27t_work_with_my_Wireless_card .21>

<quote>
It doesn't work with my Wireless card!

This is a known problem, and it is not caused by the bridge code. Many
wireless cards don't allow spoofing of the source address. It is a
firmware restriction with some chipsets. [...]

Doing full bridging of wireless (802.11) requires supporting WDS. The
current implementation doesn't do it.

It is possible to do limited wireless to Ethernet functionality with
some wireless drivers. This requires the device to be able to support a
different sender address and source address. That is what WDS provides.
<end of quote>

Any opinions ?

On Jan 6, 6:05*pm, Scott Simpson <Scott.Simp...@computer.org> wrote:
> I have a Linux computer that sits in my living room and speaks over a
> wireless network with WPA using wpa_supplicant. That works fine. This
> computer also has an ethernet card in it. I'd like to connect another
> device into that ethernet with a crossover cable and let that other
> device use DHCP to get an address from my DHCP server (which is on the
> other side of the wireless network). Do I set that ethernet card up as a
> bridge? If so, how?

O do it at home with bridge-utils and a Madwifi powered wireless
device...

Google it: bridge-utils

Pascal Hambourg <boite-a-(E-Mail Removed)> wrote:
> Huh ? What does promiscuous mode have to do with the supposedly lower
> bandwidth ? Sending traffic takes bandwidth, receiving doesn't. [...]

Two questions, two answers.

1. You can't assign multiple MACs to a wireless interface, so the only
other alternatives are promiscuous mode or proxy ARP.

2. If you bridge, you bridge. Ethernet is much faster than wireless
(obviously), so you can easily overload the wireless capability. Proxy
ARP allows you to send only the traffic that's needed over the wireless
connection.

Chris

Chris Davies a écrit :
> Pascal Hambourg <boite-a-(E-Mail Removed)> wrote:
>
>>Huh ? What does promiscuous mode have to do with the supposedly lower
>>bandwidth ? Sending traffic takes bandwidth, receiving doesn't. [...]
>
>
> Two questions, two answers.

Where did you see two questions ?

> 1. You can't assign multiple MACs to a wireless interface, so the only
> other alternatives are promiscuous mode or proxy ARP.

I don't think you can assign multiple MAC addresses to an ethernet
interface either, so what ? How would this help anyway ?

> 2. If you bridge, you bridge.

Sure. :-)

> Ethernet is much faster than wireless (obviously),

Not in all cases. Despite the terrible 802.11 protocol overhead which
divides the useful throughput by 2, I believe that wireless at a
signalling rate of 54 Mbit/s is still faster that 10Mbit/s ethernet.

> so you can easily overload the wireless capability.

Even though you're right, so what ? You can bridge ethernet ports at
different speeds and overload a low speed port from a higher speed one,
and no one complains about that. Besides, how would promiscous mode on
the wireless interface increase the load on the wireless network ?
Promiscuous mode is about receiving, not transmitting.

> Proxy ARP allows you to send only the traffic that's needed over the
> wireless connection.

Same with most of the traffic forwarded by a bridge. A bridge doesn't
blindly repeat all traffic, it can learn which port is connected to a
given MAC address. Anyway neither bridging nor proxy ARP will prevent
the wireless side from being overloaded by a faster ethernet side. And
how do you mix proxy ARP with the DHCP requirement expressed by the OP ?

Pascal Hambourg <boite-a-(E-Mail Removed)> wrote:
> Chris Davies a écrit :
>> Pascal Hambourg <boite-a-(E-Mail Removed)> wrote:
>>
>>>Huh ? What does promiscuous mode have to do with the supposedly lower
>>>bandwidth ? Sending traffic takes bandwidth, receiving doesn't. [...]
>>
>>
>> Two questions, two answers.

> Where did you see two questions ?

Maybe I'm getting tired. Or perhaps I need new eyes. What I wrote last
night was as clear as glass. When I re-read it again today I think
"huh?" :-/

I think it would be best if I bail out of this conversation. I know
what I'm trying to say but I can't get it into words. Sorry.

Chris

>> I have a Linux computer that sits in my living room and speaks over a
>> wireless network with WPA using wpa_supplicant. That works fine. This
>> computer also has an ethernet card in it. I'd like to connect another
>> device into that ethernet with a crossover cable and let that other
>> device use DHCP to get an address from my DHCP server (which is on the
>> other side of the wireless network). Do I set that ethernet card up as a
>> bridge? If so, how?

> O do it at home with bridge-utils and a Madwifi powered wireless
> device...

Where can I find such hardware?

I've seen sites that try to record which card uses which (set of)
chipsets as well as data about which drivers to use for which chipset,
but I wish someone tried to compile this info into an actual set of
recommendations. E.g. for each type of hardware (mini-pci, PCI, USB,
pcmcia, ...) it could start by listing the linux drivers by order of
quality, then for each one, list the devices that are known to *always*
use this chipset, then the devices that sometimes use it (listing which
revisions and whether they're likely to be found in *new* hardware), ...


Stefan

Stefan Monnier <(E-Mail Removed)> writes:

>> O do it at home with bridge-utils and a Madwifi powered wireless
>> device...
>
> Where can I find such hardware?

An electronics store should work, else a dedicated computer store. Do
your research. Note the exact product ID number and names available,
then check online if it will work with linux before you shell out the
money for it. I got rushed by a salesman when I tried to do this
in-store using their PC, but he assured me I could return it anyway
(which I don't like to do, ever). I got lucky, with a little research
before hand to know generally what I wanted (avoid PCMCIA, AP mode
available, drivers compile as kmods correctly and easily every time).

> I've seen sites that try to record which card uses which (set of)
> chipsets as well as data about which drivers to use for which chipset,
> but I wish someone tried to compile this info into an actual set of
> recommendations. E.g. for each type of hardware (mini-pci, PCI, USB,
> pcmcia, ...) it could start by listing the linux drivers by order of
> quality, then for each one, list the devices that are known to *always*
> use this chipset, then the devices that sometimes use it (listing which
> revisions and whether they're likely to be found in *new* hardware), ...

I'd recommend the Netgear WG311T, PCI, for a desktop-type setup. White
box with an orange stripe on the bottom. I found mine at Best Buy,
probably some in other places. You'll need the drivers off
www.madwifi.org, bride-utils (http://bridge.sourceforge.net), and
bridging/wireless/wireless exts enabled in your kernel.

00:0b.0 Ethernet controller: Atheros Communications, Inc. AR5212/AR5213 Multiprotocol MAC/baseband processor (rev 01)

For a hardware list something like you describe, I like the HCL on
http://www.linuxquestions.org/


--
[** America, the police state **]
Whoooose! What's that noise? Why, it's US citizen's
rights, going down the toilet with Bush flushing.
http://www.theregister.co.uk/2008/01..._nsa_internal/
http://www.wired.com/politics/securi...007/08/wiretap
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http://www.privacyinternational.org/...D=x-347-559597

jayjwa <(E-Mail Removed)> writes:

>Stefan Monnier <(E-Mail Removed)> writes:

>>> O do it at home with bridge-utils and a Madwifi powered wireless
>>> device...
>>
>> Where can I find such hardware?

>An electronics store should work, else a dedicated computer store. Do
>your research. Note the exact product ID number and names available,
>then check online if it will work with linux before you shell out the
>money for it. I got rushed by a salesman when I tried to do this
>in-store using their PC, but he assured me I could return it anyway
>(which I don't like to do, ever). I got lucky, with a little research
>before hand to know generally what I wanted (avoid PCMCIA, AP mode
>available, drivers compile as kmods correctly and easily every time).

Another set of chips is the intel series which have native Linux drivers--
all of them. They work well.



>> I've seen sites that try to record which card uses which (set of)
>> chipsets as well as data about which drivers to use for which chipset,

The manufacturers change chipsets without changing the name of the device.
Thus Wiresot's XL122 might have four different chipsets in its histor, at
best designated by a -1, -2 on the tiny label on the back. Thus if someone
recommended an XL122 to you and you bought it, you might well discover your
did not work with Linux while his did.

>> but I wish someone tried to compile this info into an actual set of
>> recommendations. E.g. for each type of hardware (mini-pci, PCI, USB,
>> pcmcia, ...) it could start by listing the linux drivers by order of
>> quality, then for each one, list the devices that are known to *always*
>> use this chipset, then the devices that sometimes use it (listing which
>> revisions and whether they're likely to be found in *new* hardware), ...

No one has the time or energy to do the kind of careful examination ofthe
devices to do this. Do you really want me recommending things I had never
used, or had heard from a friend of a friend that he had once used it on
Linux?



>I'd recommend the Netgear WG311T, PCI, for a desktop-type setup. White
>box with an orange stripe on the bottom. I found mine at Best Buy,
>probably some in other places. You'll need the drivers off
>www.madwifi.org, bride-utils (http://bridge.sourceforge.net), and
>bridging/wireless/wireless exts enabled in your kernel.

So, you will find this. Someone uses a device and it works for them.
Note that almost all distros include manwifi in the distro.


>00:0b.0 Ethernet controller: Atheros Communications, Inc. AR5212/AR5213 Multiprotocol MAC/baseband processor (rev 01)

>For a hardware list something like you describe, I like the HCL on
>http://www.linuxquestions.org/


>--
> [** America, the police state **]
>Whoooose! What's that noise? Why, it's US citizen's
>rights, going down the toilet with Bush flushing.
>http://www.theregister.co.uk/2008/01..._nsa_internal/
>http://www.wired.com/politics/securi...007/08/wiretap
>http://www.hermes-press.com/police_state.htm
>http://www.privacyinternational.org/...D=x-347-559597