Question for Jeff Liebermann

Hi Jeff,

I found an old post of yours where you said "DD-WRT and OpenWRT both
have a bridging mode. However, it's not
exactly transparent bridging and may cause problems if you expect
transparent bridging."

I've got an old Win98 computer with PCI 2.1 slots, and I wanted to
give it wireless access using WPA encryption. Seems like most/all
wireless adapters today don't support WPA on Win98 and also require
PCI 2.2 slots. So I was thinking of getting an Asus WL-520gU router
and using DD-WRT to set it up as a wireless bridge for the Win98
machine to talk to my Linksys WRT54GL wireless access point. I was
wondering what you meant by "transparent bridging". Would my scenario
require transparent bridging? How would using the DD-WRT bridging be
different than if I had a wireless PCI card in the computer? What
could or couldn't I do?

Thanks for any help.

On Oct 22, 12:17 am, Jeff Liebermann <je...@cruzio.com> wrote:
> >How would using the DD-WRT bridging be
> >different than if I had a wireless PCI card in the computer?
>
> I don't understand what you're asking. Functionally, with one
> computah, they're identical.

So the only difference would be that machines in front of the bridge
would think that the Win98 machine has a MAC address equivalent to the
bridge's MAC address? And there would be no way that they could tell
there's a bridge? I did read that you could set up the bridge to
clone the MAC of the machine behind it, so that the Win98 machine
wouldn't even have its MAC address changed.

>
> >What could or couldn't I do?
>
> I'm not sure exactly what will fail if you build a network behind a
> client mode radio (the one with multiple IP's on a single MAC). If I
> think of something, I'll post it.

I was thinking of attaching 2 computers to the WL-520gU, although now
that I know there could be issues with that, I probably won't do it.
Do you have any recommendations for routers that support transparent
bridging? Thanks.

I got the WL-520gU, and I flashed it with DD-WRT and set it up as a
client bridge. It talks to my WAP, which sits behind a router. The
bridge seems to be working, as the computer attached to it can get on
the internet, but there seems to be one problem I noticed. While
testing the bridge, I would plug the computer directly into the
bridge, and then plug it directly into the router, and back and
forth. I noticed that whenever I plugged the computer into the
bridge, the computer could not get on the internet, and it couldn't
ping the router either. I would have to power-cycle the router before
the computer could get on the internet. Any idea what that's about?

On Oct 28, 2:38*am, Jeff Liebermann <je...@cruzio.com> wrote:
> On Mon, 27 Oct 2008 10:19:41 -0700 (PDT), "void.no.spam....@gmail.com"
>
> <void.no.spam....@gmail.com> wrote:
> >I got the WL-520gU, and I flashed it with DD-WRT and set it up as a
> >client bridge. *It talks to my WAP, which sits behind a router. *The
> >bridge seems to be working, as the computer attached to it can get on
> >the internet, but there seems to be one problem I noticed. *While
> >testing the bridge, I would plug the computer directly into the
> >bridge, and then plug it directly into the router, and back and
> >forth. *I noticed that whenever I plugged the computer into the
> >bridge, the computer could not get on the internet, and it couldn't
> >ping the router either. *I would have to power-cycle the router before
> >the computer could get on the internet. *Any idea what that's about?
>
> Nothing wrong. *You computah is retaining the MAC address of the
> router in the ARP table. *Run:
> * arp -a
> to dump the current MAC -> IP address values. *When you move the
> connection to wireless, the IP address (of the router) doesn't change,
> but the MAC address does. *Same problem at the router, which
> previously had the MAC address of your ethernet card for your PC, but
> now has the MAC address of the wireless card for the same IP address.

So then shouldn't my computer have the same problem when I connect it
directly to the router, after it has been working behind the wireless
bridge? But it has no problem moving from bridge to router.

> Most PC's are fairly smart about recognizing the change, but it's
> possible to configure your unspecified operating system to fail to
> recognize the change. *Power cycling the router is one way to clear
> the ARP table. *You can run:
> * arp -d ip_address_of_the_router
> or possibly:
> * ipconfig /release
> * ipconfig /renew
> to kick start the boxes.

Here is what I have seen tonight:

With my computer plugged into the router and able to access the
internet, doing an "arp -a" on the computer shows 192.168.1.1 with the
router's MAC, and the router's web site shows my computer's IP with
the ethernet card MAC.

Then after plugging the computer into the wireless bridge, I can't
ping the router. Trying a "arp -d 192.168.1.1" doesn't help the
computer ping the router. I have to do "ipconfig /release" and
"ipconfig /renew" and then my computer is able to ping the router and
go on the internet. But then "arp -a" still shows 192.168.1.1 with
the router's MAC, and the router's web site still shows my computer's
IP with the ethernet card MAC. I don't see the MAC of the wireless
bridge anywhere. Does that sound right? (Note that I am not doing
any MAC cloning on the bridge.)

> Look for a check box on the operating systems ethernet setup with
> something like "detect media changes". *It should be checked.

I am running Windows 2000, and I don't see any sort of "detect media
changes" option anywhere. I also looked at that route metric problem
link you provided, and it seems to be a new feature in XP, so that
wouldn't affect my computer.

On Oct 29, 6:45*am, Jeff Liebermann <je...@cruzio.com> wrote:
> On Tue, 28 Oct 2008 20:49:03 -0700 (PDT), "void.no.spam....@gmail.com"
>
> <void.no.spam....@gmail.com> wrote:
> >So then shouldn't my computer have the same problem when I connect it
> >directly to the router, after it has been working behind the wireless
> >bridge? *But it has no problem moving from bridge to router.
>
> Yes, that would seem logical. *However, I note from your original
> posting that you're using Windoze 98. *I have no clue how it would be
> expected to respond. *I'm going to do myself a big favor and not
> excavate an old W98SE laptop and see. *Incidentally, if it's Win98SE
> (second edition), you have a chance of getting things working. *If
> it's the original Win98, or Win98SE without any updates, give up while
> you're still sane.

Yeah I do have a computer with Win98SE and updates.

> >Here is what I have seen tonight:
>
> >With my computer plugged into the router and able to access the
> >internet, doing an "arp -a" on the computer shows 192.168.1.1 with the
> >router's MAC, and the router's web site shows my computer's IP with
> >the ethernet card MAC.
>
> >Then after plugging the computer into the wireless bridge, I can't
> >ping the router. *Trying a "arp -d 192.168.1.1" doesn't help the
> >computer ping the router. *I have to do "ipconfig /release" and
> >"ipconfig /renew" and then my computer is able to ping the router and
> >go on the internet. *But then "arp -a" still shows 192.168.1.1 with
> >the router's MAC, and the router's web site still shows my computer's
> >IP with the ethernet card MAC.
>
> That's because the web page(s) are in the web browsers cache. *Can you
> change pages in the web browser? *(especially one's that you have seen
> before)?

After doing the "ipconfig /release" and "ipconfig /renew", I can visit
pages that I never visited before in the browser.

>
> >I don't see the MAC of the wireless
> >bridge anywhere. *Does that sound right? *(Note that I am not doing
> >any MAC cloning on the bridge.)
>
> You're right (I'm wrong). *The computer should show the router MAC
> address in arp -a, not that of the wireless bridge. *If you ping the
> IP address of the Asus WL-520gU running DD-WRT in client mode, you
> should see both the WRT54GL router and the client adapter with arp -a.

OK, after pinging the WL-520gU, I see them both in the "arp -a"
output.

>
> At this point, I'm not sure where the problem is hiding. *Something is
> having a problem deciding whether packets should go via ethernet or
> wireless, but I can't tell from here.

At least I know of a couple workarounds now.

> >> Look for a check box on the operating systems ethernet setup with
> >> something like "detect media changes". *It should be checked.
>
> >I am running Windows 2000,
>
> That's good to know. *Please re-read your original posting and explain
> where you switched from Windoze 98 to Windoze 2000.
> * *"I've got an old Win98 computer with PCI 2.1 slots, and
> * *I wanted to give it wireless access using WPA encryption."

Yes, I will eventually move the bridge to be connected with my Win98
machine, although right now it is a little more convenient for me to
test it out with my Win2000 machine. And the Win2000 machine may need
wireless access at some point in the future, so it doesn't hurt to see
if it works there too.

>
> >and I don't see any sort of "detect media
> >changes" option anywhere.
>
> See:
> <http://www.windowsreference.com/networking/disable-media-sensing-on-e...>
> In Win98, it was up to the ethernet driver manufacture how this was
> set. *Some, particularly laptops, had some fairly creative default
> setups. *In 2000 and XP, it's on by default. *Some drivers have check
> boxes or settings to change it.

Looks like mine is on, according to the lack of that registry entry
mentioned in the link you provided.

>
> >I also looked at that route metric problem
> >link you provided, and it seems to be a new feature in XP, so that
> >wouldn't affect my computer.
>
> The route metric is in every version of Windoze since the stone age.
> The problem is that each version and some updates behave differently.

Thanks for the help, Jeff.