DHCP over a dd-wrt client bridge.

[Les Cargill]

What's involved:
A WRT54G v8, original firmware, hooked to cable modem.
Another WRT54G v8, using dd-wrt* acting as a dd-wrt
client wireless bridge. DD-WRT v24 RC-4 (10/10/07) micro - build 8151M

The offending desktop is connected to the dd-wrt wireless bridge.
It is running an ancient pre-SP1 version of XP Home, which has
a nauseatingly incorrect IP stack. Very NT.

What I have found is that this works:

1) Hook up wired to the backhaul router.
2) Do the DHCP thing.
3) Disconnect from the backhaul router.
4) Reboot workstation, connected to the wireless client bridge.
5) Workstation gets the same IP address.

So, we add another (modern) workstation with a USB 802.11G thumb drive
which carps the IP address of the old computer.

The workstation does not appear to get a DHCP response back and shrugs,
chooses a 169.154.0.0 appropriate address.

I tried this with the horrible old XP version but I also got exactly
the same results with a Knoppix boot-from-CD. The DHCP response
times out.

I conclude that the dd-wrt wireless bridge does not forward
broadcasts* to the main wireless router, and DHCP cannot be made to
work properly over this arrangement. Yes, the answer is a fixed IP,
and I'll do it as soon as I have backed up all 16 GB of stuff off
the offending machine.

*I'm not sure of the layer, but I think it's a clue.

Once I have my story straight, I'll ply the waters of the dd-wrt
community again.

--
Les Cargill

[Jeff Liebermann]

Les Cargill <lcargill@cfl.rr.com> hath wroth:

>A WRT54G v8, original firmware, hooked to cable modem.
>Another WRT54G v8, using dd-wrt* acting as a dd-wrt
>client wireless bridge. DD-WRT v24 RC-4 (10/10/07) micro - build 8151M

Try DD-WRT v24 RC-6.1
<http://www.dd-wrt.com/dd-wrtv2/down.php?path=downloads%2Frelease+candidates/>

>I conclude that the dd-wrt wireless bridge does not forward
>broadcasts* to the main wireless router, and DHCP cannot be made to
>work properly over this arrangement.

Yeah, that's possible. Meanwhile, do some sniffing with Ethereal or
Wireshark to see what's happening.

Under XP, try running a DHCP query tool:
<http://www.weirdsolutions.com/weirdSolutions/files/products/desktopSoftware/desktopQueryTool/querytool_free.exe>
Type literally anything into the "Device Identifier" box. It can't be
blank. Check the "request broadcast response" box. Do NOT check the
"Use BOOTP" box.

There's also a Linux version at:
<http://www.weirdsolutions.com/weirdSolutions/files/products/desktopSoftware/desktopQueryTool/querytool.i586.rpm>

What I get is:
option PKT:Opcode=2
option PKT:HType=1
option PKT:HLen=1
option PKT:Hops=0
option DHCP message type=5
option PKT:Flags=32768
option PKT:Seconds=0
option PKT:XID=41
option PKT:SName=
option PKT:Boot file=
option PKT:CIAddr=0.0.0.0
option PKT:YIAddr=192.168.1.100
option PKT:SIAddr=192.168.1.1
option PKT:GIAddr=0.0.0.0
option PKT:Magic cookie=99.130.83.99
option Subnet mask=255.255.255.0
option Gateways=192.168.1.1
option Domain name servers=192.168.1.1
option Broadcast address=192.168.1.255
option Server identifier=192.168.1.1
option DHCP address lease time=7200
option DHCP renewal time=3600
option DHCP rebinding time=6300
option PKT:CHAddr=00
--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Les Cargill]

Jeff Liebermann wrote:
> Les Cargill <lcargill@cfl.rr.com> hath wroth:
>
>> A WRT54G v8, original firmware, hooked to cable modem.
>> Another WRT54G v8, using dd-wrt* acting as a dd-wrt
>> client wireless bridge. DD-WRT v24 RC-4 (10/10/07) micro - build 8151M
>
> Try DD-WRT v24 RC-6.1
> <http://www.dd-wrt.com/dd-wrtv2/down.php?path=downloads%2Frelease+candidates/>
>

I realize this is not a dd-wrt support forum, but is there a blurb
on the website which helps navigate which branch of that release is
most appropriate for what platform? I suspect the "generic" is
the right answer, but I can't really defend that suspicion :)

Just trudging through the forums is kinda slow :)

>> I conclude that the dd-wrt wireless bridge does not forward
>> broadcasts* to the main wireless router, and DHCP cannot be made to
>> work properly over this arrangement.
>
> Yeah, that's possible. Meanwhile, do some sniffing with Ethereal or
> Wireshark to see what's happening.
>

FWIW, using KNOPPIX, I get a DHCP timeout. I'm in the process of backing
this machine up to reinstall Doze - it won't even allow setting a fixed
IP without crashing.

This is an *OLD* version of XP, 2002-2001 vintage. Meh. If all else,
I'll rig up a .bat file with a rarp command.

> Under XP, try running a DHCP query tool:
> <http://www.weirdsolutions.com/weirdSolutions/files/products/desktopSoftware/desktopQueryTool/querytool_free.exe>
> Type literally anything into the "Device Identifier" box. It can't be
> blank. Check the "request broadcast response" box. Do NOT check the
> "Use BOOTP" box.
>
> There's also a Linux version at:
> <http://www.weirdsolutions.com/weirdSolutions/files/products/desktopSoftware/desktopQueryTool/querytool.i586.rpm>
>
> What I get is:
> option PKT:Opcode=2
> option PKT:HType=1
> option PKT:HLen=1
> option PKT:Hops=0
> option DHCP message type=5
> option PKT:Flags=32768
> option PKT:Seconds=0
> option PKT:XID=41
> option PKT:SName=
> option PKT:Boot file=
> option PKT:CIAddr=0.0.0.0
> option PKT:YIAddr=192.168.1.100
> option PKT:SIAddr=192.168.1.1
> option PKT:GIAddr=0.0.0.0
> option PKT:Magic cookie=99.130.83.99
> option Subnet mask=255.255.255.0
> option Gateways=192.168.1.1
> option Domain name servers=192.168.1.1
> option Broadcast address=192.168.1.255
> option Server identifier=192.168.1.1
> option DHCP address lease time=7200
> option DHCP renewal time=3600
> option DHCP rebinding time=6300
> option PKT:CHAddr=00

I get nothing on the main machine hooked wired Ethernet directly to the
router that is the DHCP server. :( That path does not include the dd-wrt
box at all.

The machine that cannot DCHP wirelessly can DHCP wired.

The MAC already has a DHCP supplied IP address, so I don't blame it. Un
fortunately, the machine in quesiton is in use. I'll hook Ethereal up
later.

Thanks much, Jeff.

--
Les Cargill

[Jeff Liebermann]

Les Cargill <lcargill@cfl.rr.com> hath wroth:

>I realize this is not a dd-wrt support forum, but is there a blurb
>on the website which helps navigate which branch of that release is
>most appropriate for what platform?

Not really. You can lookup your specific model and mutation in:
<http://www.dd-wrt.com/wiki/index.php/Installation>
but the option of which version to install is often missing.

With your WRT54G v8, you're limited to only the micro version.
<http://www.dd-wrt.com/wiki/index.php/Linksys_WRT54G/GL/GS/GX#v8>

I don't have a magic formula for optimizing the firmware release for
specific routers. I tend to use the "no-kaid" version, because I
don't need to play game server and can use the extra RAM.

>I suspect the "generic" is
>the right answer, but I can't really defend that suspicion :)

Nope. It varies by model number and version.
Downloads -> Release Candidates (the lastest) -> Version ->
Broadcom -> Linksys -> WRT_54G_v8 -> dd-wrt.v24_micro_generic.bin
This organization is new, but is a big improvement over the previous
muddle.

>I get nothing on the main machine hooked wired Ethernet directly to the
>router that is the DHCP server. :( That path does not include the dd-wrt
>box at all.

Hint: I have no clue what machine you have, or which one is the
"main" machine. Try to be less ambiguous.

>The machine that cannot DCHP wirelessly can DHCP wired.

Is that the "main" machine, Widoze machine, Knoppix machine, or
something else? You see the problem?

The DHCP query tool usually works. It even works on my desktop, which
is setup for a static IP address, but can query the DHCP server to see
if an IP is available. It also works with multiple DHCP servers, will
overlapping addresses, but makes a bit of a mess.

Good luck.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Les Cargill]

Jeff Liebermann wrote:
> Les Cargill <lcargill@cfl.rr.com> hath wroth:
>
>> I realize this is not a dd-wrt support forum, but is there a blurb
>> on the website which helps navigate which branch of that release is
>> most appropriate for what platform?
>
> Not really. You can lookup your specific model and mutation in:
> <http://www.dd-wrt.com/wiki/index.php/Installation>
> but the option of which version to install is often missing.
>

Yup.

> With your WRT54G v8, you're limited to only the micro version.
> <http://www.dd-wrt.com/wiki/index.php/Linksys_WRT54G/GL/GS/GX#v8>
>
> I don't have a magic formula for optimizing the firmware release for
> specific routers. I tend to use the "no-kaid" version, because I
> don't need to play game server and can use the extra RAM.
>

Understood.

>> I suspect the "generic" is
>> the right answer, but I can't really defend that suspicion :)
>
> Nope. It varies by model number and version.
> Downloads -> Release Candidates (the lastest) -> Version ->
> Broadcom -> Linksys -> WRT_54G_v8 -> dd-wrt.v24_micro_generic.bin
> This organization is new, but is a big improvement over the previous
> muddle.
>

Right. And then there are like... six versions under *that* :) Ah
well....

>> I get nothing on the main machine hooked wired Ethernet directly to the
>> router that is the DHCP server. :( That path does not include the dd-wrt
>> box at all.
>
> Hint: I have no clue what machine you have, or which one is the
> "main" machine. Try to be less ambiguous.
>

Well, I wanted to stop short of numbering them :)

"hooked wired Ethernet" as opposed to "machine connected only by
wireless".

The point is that the second, wireless-bridged
WRT54G does not forward DHCP in some direction or another. This
primary, Linksys-firmware WRT54G does transmit DHCP, either on
the Ethernet switch or over the air.

This conclusion is supported by the indicated DHCP utilities. Thanks
for that.


>> The machine that cannot DCHP wirelessly can DHCP wired.
>
> Is that the "main" machine, Widoze machine, Knoppix machine, or
> something else? You see the problem?
>

Sure.

> The DHCP query tool usually works. It even works on my desktop, which
> is setup for a static IP address, but can query the DHCP server to see
> if an IP is available. It also works with multiple DHCP servers, will
> overlapping addresses, but makes a bit of a mess.
>

Excellent. Thanks much for the pointer.

> Good luck.
>

'Preciate it. I'll do any further research on the DD-WRT forum - it's
a much more appropriate place. It's kind of scary in there, though...
quite a little subculture.

--
Les Cargill

[Les Cargill]

<snip>

http://www.dd-wrt.com/phpBB2/viewtopic.php?t=23683&highlight=dhcp+bridge

For reference: DHCP does not work unless you use WDS.

--
Les Cargill

[Jeff Liebermann]

Les Cargill <lcargill@cfl.rr.com> hath wroth:

><snip>
>
>http://www.dd-wrt.com/phpBB2/viewtopic.php?t=23683&highlight=dhcp+bridge
>
>For reference: DHCP does not work unless you use WDS.

Retch. DHCP *SHOULD* work through a wireless bridge (if it will pass
broadcast packets). Using WDS seems like a band-aid or work around
for a bug. I have a funny feeling there's some interaction with WOL
(Wake on LAN) which also uses an all 1's broadcast packet. If the
micro version supports WOL, try turning it on and see if it now passes
broadcast packets. You can also use a WOL client to generate
broadcasts to 255.255.255.255 to see if they make it through the
bridge.

If you get a usable answer from the DD-WRT folks, I would be
interested.

Hmmm... I just checked the Bug Tracker and couldn't find anything
directly related to v25 RC4 and DHCP. There are a few DHCP bug
reports, but I'm discounting any reports without corroberating details
(i.e. clueless bug report). I don't see anything on the most recent
50 bug reports:
<http://www.dd-wrt.com/dd-wrtv2/bugtracker/view_all_bug_page.php>

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Jeff Liebermann]

Les Cargill <lcargill@cfl.rr.com> hath wroth:

>> Nope. It varies by model number and version.
>> Downloads -> Release Candidates (the lastest) -> Version ->
>> Broadcom -> Linksys -> WRT_54G_v8 -> dd-wrt.v24_micro_generic.bin
>> This organization is new, but is a big improvement over the previous
>> muddle.
>>
>
>Right. And then there are like... six versions under *that* :) Ah
>well....

Well, I thought it was obvious, but I guess not. I was going to point
you to:
<http://www.dd-wrt.com/wiki/index.php/What_is_DD-WRT%3F#File_Versions>
but it's old, incomplete, and not very useful.

For your Linksys WRT54G v8:
dd-wrt.v24_micro_generic.bin Generic version
dd-wrt.v24_micro_olsrd_generic.bin OLSRD Generic
dd-wrt.v24_micro_olsrd_we800g.bin OLSRD for Motorola WE800G
dd-wrt.v24_micro_olsrd_wr850g.bin OLSRD for Motorola WR850G
dd-wrt.v24_micro_we800g.bin Motorola WE800G
dd-wrt.v24_micro_wr850g.bin Motorola WR850G

OLSRD:
<http://en.wikipedia.org/wiki/Optimized_Link_State_Routing_protocol>
is an ad-hoc protocol used for mesh wireless networks.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Les Cargill]

Jeff Liebermann wrote:
> Les Cargill <lcargill@cfl.rr.com> hath wroth:
>
>> <snip>
>>
>> http://www.dd-wrt.com/phpBB2/viewtopic.php?t=23683&highlight=dhcp+bridge
>>
>> For reference: DHCP does not work unless you use WDS.
>
> Retch. DHCP *SHOULD* work through a wireless bridge (if it will pass
> broadcast packets).

If it's a MAC layer broadcast, that could be a problem. Multicast
won't work - the firmware appears to simply hardcode a MAC address
for each port. So it's not a true transparent bridge. I don't think
plain-old ports on the switch will want to forward promiscuously. We've
kind of inverted the original intended topology of the device by making
the wireless MAC the backhaul.


Also, when I dump the arp cache on YET ANOTHER workstation :), I get the
same MAC assigned to both the IP address for the client-bridge router
(192.168.1.2) and a workstation connected to the Ethernet switch on that
router (192.168.1.49)

C:\Documents and Settings\Owner>arp -a

Interface: 192.168.1.102 --- 0x10004
Internet Address Physical Address Type
192.168.1.1 00-1c-10-b0-32-eb dynamic
192.168.1.2 00-1c-10-ae-1b-76 dynamic
192.168.1.49 00-1c-10-ae-1b-76 dynamic
192.168.1.100 00-40-ca-90-f1-0b dynamic

C:\Documents and Settings\Owner>

For clarity:

Main machine - connected wired to WAP which has a cable modem on the
WAN port. 192.168.1.100 and 192.168.1.1 respectively.

Second machine - wired to client-bridged WRT54G - 1.49 and 1.2

*Third* machine - USB 802.11G adapter elsewhere. The "arp -a" is done
from there.

Not sure that this matters. Doesn't seem very bridge-like -
a real learning bridge has no MAC address *per se*(1). Might
have one in CAM for its own purposes ( inband traffic terminating
at a CPU off the bridge... ).

(1) been a while - there may be an exception I'm missing, and
it may have been colored by the equipment I was working with.

> Using WDS seems like a band-aid or work around
> for a bug. I have a funny feeling there's some interaction with WOL
> (Wake on LAN) which also uses an all 1's broadcast packet. If the
> micro version supports WOL, try turning it on and see if it now passes
> broadcast packets.

It does. Will do.

> You can also use a WOL client to generate
> broadcasts to 255.255.255.255 to see if they make it through the
> bridge.
>
> If you get a usable answer from the DD-WRT folks, I would be
> interested.
>

I'll put a little effort into that, then. My workaround for
the moment is a static IP, but the least I can do for the
guys is due diligence to get it on the scope.

> Hmmm... I just checked the Bug Tracker and couldn't find anything
> directly related to v25 RC4 and DHCP. There are a few DHCP bug
> reports, but I'm discounting any reports without corroberating details
> (i.e. clueless bug report). I don't see anything on the most recent
> 50 bug reports:
> <http://www.dd-wrt.com/dd-wrtv2/bugtracker/view_all_bug_page.php>
>

Lemme start a thread on the website. It seems odd that this would go
unnoticed - indeed, it hasn't - maybe just not noticed by the right people.

--
Les Cargill

[Les Cargill]

Jeff Liebermann wrote:
> Les Cargill <lcargill@cfl.rr.com> hath wroth:
>
>>> Nope. It varies by model number and version.
>>> Downloads -> Release Candidates (the lastest) -> Version ->
>>> Broadcom -> Linksys -> WRT_54G_v8 -> dd-wrt.v24_micro_generic.bin
>>> This organization is new, but is a big improvement over the previous
>>> muddle.
>>>
>> Right. And then there are like... six versions under *that* :) Ah
>> well....
>
> Well, I thought it was obvious,

It would be to the trained eye... :)

> but I guess not. I was going to point
> you to:
> <http://www.dd-wrt.com/wiki/index.php/What_is_DD-WRT%3F#File_Versions>
> but it's old, incomplete, and not very useful.
>
> For your Linksys WRT54G v8:
> dd-wrt.v24_micro_generic.bin Generic version
> dd-wrt.v24_micro_olsrd_generic.bin OLSRD Generic
> dd-wrt.v24_micro_olsrd_we800g.bin OLSRD for Motorola WE800G
> dd-wrt.v24_micro_olsrd_wr850g.bin OLSRD for Motorola WR850G
> dd-wrt.v24_micro_we800g.bin Motorola WE800G
> dd-wrt.v24_micro_wr850g.bin Motorola WR850G
>
> OLSRD:
> <http://en.wikipedia.org/wiki/Optimized_Link_State_Routing_protocol>
> is an ad-hoc protocol used for mesh wireless networks.
>

Ah! That's what I was missing. And that's what I originally meant
by "generic", but I was trying to gather supporting data for
the guess.

>
>

Thanks!

--
Les Cargill

[Les Cargill]

Les Cargill wrote:
> Jeff Liebermann wrote:
>> Les Cargill <lcargill@cfl.rr.com> hath wroth:
>>
>>> <snip>
>>>
>>> http://www.dd-wrt.com/phpBB2/viewtopic.php?t=23683&highlight=dhcp+bridge
>>>
>>> For reference: DHCP does not work unless you use WDS.
>>
>> Retch. DHCP *SHOULD* work through a wireless bridge (if it will pass
>> broadcast packets).
>
> If it's a MAC layer broadcast, that could be a problem. Multicast
> won't work - the firmware appears to simply hardcode a MAC address
> for each port. So it's not a true transparent bridge. I don't think
> plain-old ports on the switch will want to forward promiscuously. We've
> kind of inverted the original intended topology of the device by making
> the wireless MAC the backhaul.
>
>
> Also, when I dump the arp cache on YET ANOTHER workstation :), I get the
> same MAC assigned to both the IP address for the client-bridge router
> (192.168.1.2) and a workstation connected to the Ethernet switch on that
> router (192.168.1.49)
>
> C:\Documents and Settings\Owner>arp -a
>
> Interface: 192.168.1.102 --- 0x10004
> Internet Address Physical Address Type
> 192.168.1.1 00-1c-10-b0-32-eb dynamic
> 192.168.1.2 00-1c-10-ae-1b-76 dynamic
> 192.168.1.49 00-1c-10-ae-1b-76 dynamic
> 192.168.1.100 00-40-ca-90-f1-0b dynamic
>
> C:\Documents and Settings\Owner>
>
> For clarity:
>
> Main machine - connected wired to WAP which has a cable modem on the
> WAN port. 192.168.1.100 and 192.168.1.1 respectively.
>
> Second machine - wired to client-bridged WRT54G - 1.49 and 1.2
>
> *Third* machine - USB 802.11G adapter elsewhere. The "arp -a" is done
> from there.
>
> Not sure that this matters. Doesn't seem very bridge-like -
> a real learning bridge has no MAC address *per se*(1). Might
> have one in CAM for its own purposes ( inband traffic terminating
> at a CPU off the bridge... ).
>
> (1) been a while - there may be an exception I'm missing, and
> it may have been colored by the equipment I was working with.
>
>> Using WDS seems like a band-aid or work around
>> for a bug. I have a funny feeling there's some interaction with WOL
>> (Wake on LAN) which also uses an all 1's broadcast packet. If the
>> micro version supports WOL, try turning it on and see if it now passes
>> broadcast packets.
>
> It does. Will do.
>
>> You can also use a WOL client to generate
>> broadcasts to 255.255.255.255 to see if they make it through the
>> bridge.
>>
>> If you get a usable answer from the DD-WRT folks, I would be
>> interested.
>
> I'll put a little effort into that, then. My workaround for
> the moment is a static IP, but the least I can do for the
> guys is due diligence to get it on the scope.
>
>> Hmmm... I just checked the Bug Tracker and couldn't find anything
>> directly related to v25 RC4 and DHCP. There are a few DHCP bug
>> reports, but I'm discounting any reports without corroberating details
>> (i.e. clueless bug report). I don't see anything on the most recent
>> 50 bug reports:
>> <http://www.dd-wrt.com/dd-wrtv2/bugtracker/view_all_bug_page.php>
>>
>
> Lemme start a thread on the website. It seems odd that this would go
> unnoticed - indeed, it hasn't - maybe just not noticed by the right people.
>
> --
> Les Cargill

I sit corrected - they know.
http://www.dd-wrt.com/phpBB2/viewtopic.php?t=68

It's not a transparent bridge.

--
Les Cargill

[Jeff Liebermann]

Les Cargill <lcargill@cfl.rr.com> hath wroth:

>I sit corrected - they know.
>http://www.dd-wrt.com/phpBB2/viewtopic.php?t=68
>
>It's not a transparent bridge.

Yep. I was going try and find that thread. Note that about half the
repies indicate that DHCP should work behind a DD-WRT client.
Unfortunately, there are about an equal number of "it works" and "it
doesn't work" posting, with little substantiations. Even if there was
some complication with assigning multiple IP's to a single MAC
(perfectly legal as in multi-homed) you would still get at least *ONE*
DHCP assigned IP address to the first client to connect.

Also note item 6 in the first article:
... The main router will handle DHCP for any and all devices
connected, whether it be on the normal wlan or behind the
client bridge - it won't matter which.
In other words, DHCP should work.

Look at the 2nd reply in that article... the one that lists the output
of arp -a for a transparent bridge and for DD-WRT in client mode. Note
that the 2nd apr -a example, for the DD-WRT client, shows multipile
IP's for a single MAC. However, also note that all the entries are
listed as "dynamic" which means they came from a DHCP server
somewhere.

Now, there's a possibility that the author faked the results, or has a
DHCP server running on his client, or some other oddity, but it would
appear that DHCP worked for him with DD-WRT.

Incidentally, I've never heard of semi-MAC-Address-Translation (MAT)
or a MAC proxy. I couldn't find anything on it with Google. Weird.

These might be worth digesting:
<http://www.dd-wrt.com/wiki/index.php/Client_Mode_Wireless>
<http://www.wi-fiplanet.com/tutorials/article.php/3639271>



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558