bridging two wireless interfaces

Hi,

please help and comment as much as you think is needed,
since I feel that I must be missing many things.

I am experimenting with "bridging two wireless interfaces"
on [my notebook]. I don't really know what I want, but I guess
I want to "see" packets going through the layer 2 of the stack
on [my notebook] and may be I could expect to extend the range
of my wireless [AP] using [my notebook] configured as a
"wireless bridge"?

Is this not what is meant by "bridging"? Have I put them
all ok?

The wireless [AP] is the gateway to the internet using the ESSID
default and channel 6. The eth1 (put in managed mode) of my
notebook associates to this [AP]. The other wireless iface ath0
put in the master mode, same ESSID and channel, (or should
I have used a different channel? Anyway, I've tried both),



[her laptop] [my notebook]
+-------------------+ 192.168.0.1
| | DHCPD
Do I "see" ----+-ath0 br0 eth1-+------- wireless [AP]
the [AP] here | 192.168.0.200 | "default"
via channel 4 +-------------------+ channel 6
on another master managed 00:90:96:28:3E:EB
laptop? "default" "default"
channel 4 channel 6
00:11:F5:8D:8E:85 00:90:96:28:3E:EB
(madwifi) (orinoco_cs)


# ifconfig ath0 0.0.0.0 down
# ifconfig eth1 0.0.0.0 down
# brctl addbr br0
# brctl addif br0 eth1
# brctl addif br0 ath0
# ifconfig br0 192.168.0.200 up
# ifconfig ath0 up
# ifconfig eth1 up
# brctl stp br0 on (Well, what's a "spanning tree"?)
# brctl show

bridge name bridge id STP enabled interfaces
br0 8000.0011f58d8e85 yes ath0
eth1

# brctl showstp br0

br0
bridge id 8000.0011f58d8e85
designated root 8000.0011f58d8e85
root port 0 path cost
0
max age 19.99 bridge max age
19.99
hello time 1.99 bridge hello time
1.99
forward delay 14.99 bridge forward delay
14.99
ageing time 299.95
hello timer 1.61 tcn timer
0.00
topology change timer 0.00 gc timer
0.03
flags


ath0 (2)
port id 8002 state
disabled

^^^^^^^^^^^^^
#### Why is the ath0(2) "disabled" and how do I enable it?
It is up and I do not understand these things ...

designated root 8000.0011f58d8e85 path cost
100
designated bridge 8000.0011f58d8e85 message age timer
0.00
designated port 8002 forward delay timer
0.00
designated cost 0 hold timer
0.00
flags

eth1 (1)
port id 8001 state
forwarding
designated root 8000.0011f58d8e85 path cost
100
designated bridge 8000.0011f58d8e85 message age timer
0.00
designated port 8001 forward delay timer
0.00
designated cost 0 hold timer
0.61
flags


`iwconfig` on [my notebook]:
==================================================

ath0 IEEE 802.11b ESSID:"default"
Mode:Master Frequency:2.427 GHz Access Point:
00:11:F5:8D:8E:85
Bit Rate:0 kb/s Tx-Power:18 dBm Sensitivity=0/3
Retryff RTS thrff Fragment thrff
Power Managementff
Link Quality=56/94 Signal level=-39 dBm Noise level=-95 dBm
Rx invalid nwid:2737 Rx invalid crypt:0 Rx invalid frag:0
Tx excessive retries:598 Invalid misc:598 Missed beacon:4

eth1 IEEE 802.11b ESSID:"default" Nickname:"HERMES I"
Mode:Managed Frequency:2.427 GHz Access Point:
00:11:F5:8D:8E:85
Bit Rate:2 Mb/s Sensitivity:1/3
Retry limit:4 RTS thrff Fragment thrff
Power Managementff
Link Quality=65/92 Signal level=-30 dBm Noise level=-95 dBm
Rx invalid nwid:0 Rx invalid crypt:7823 Rx invalid frag:81
Tx excessive retries:1 Invalid misc:0 Missed beacon:0

br0 no wireless extensions.

`ifconfig` on [my notebook]:
==================================================

ath0 Link encap:Ethernet HWaddr 00:11:F5:8D:8E:85
UP BROADCAST MULTICAST MTU:1500 Metric:1
RX packets:779 errors:86953 dropped:0 overruns:0 frame:86953
TX packets:462 errors:598 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:200
RX bytes:206471 (201.6 KiB) TX bytes:61440 (60.0 KiB)
Interrupt:11 Memory:df840000-df850000

br0 Link encap:Ethernet HWaddr 00:11:F5:8D:8E:85
inet addr:192.168.0.200 Bcast:192.168.0.255
Mask:255.255.255.0
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:33 errors:0 dropped:0 overruns:0 frame:0
TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:0
RX bytes:3162 (3.0 KiB) TX bytes:0 (0.0 b)

eth1 Link encap:Ethernet HWaddr 00:02:2D:88:49:68
UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
RX packets:12295 errors:6375 dropped:6375 overruns:0
frame:6375
TX packets:7 errors:1 dropped:0 overruns:0 carrier:0
collisions:0 txqueuelen:1000
RX bytes:2919469 (2.7 MiB) TX bytes:848 (848.0 b)
Interrupt:3 Base address:0xb100

Now I'd better put some explicit questions to reveal what
I'm probably missing.

1. Now that I have a dhcpd running on the [AP], if I go to
[her laptop] I suppose I could talk to the [AP] via
ath0 on channel 4, right? But nothing happened if
I try to boot [her laptop] using a dhcp-client.
No response is seen on [her laptop] upon DHCPDISCOVER.

2. I have assigned an IP 192.168.0.200 to the br0 on
[my notebook], since the [AP] is using 192.168.0.1.
I then do

route add default gw 192.168.0.1 dev br0

and tried to ping the [AP] at 192.168.0.1. But nothing
happended.

3. The ath0 on [my notebook] does not seem to be forwarding
packets. What's wrong here?

4. I go to [my notebook] and changed the essid to "test".
But this did not help.

5. cat /proc/sys/net/ipv4/ip_forward
1

but I think this is irrelevant, isn't it?

6. ....

Thanks in advance for any enlightening!

(E-Mail Removed) writes:

>Hi,

>please help and comment as much as you think is needed,
>since I feel that I must be missing many things.

>I am experimenting with "bridging two wireless interfaces"
>on [my notebook]. I don't really know what I want, but I guess

You really have to figure out what you want first.

>I want to "see" packets going through the layer 2 of the stack

Why do you you want to see them?

>on [my notebook] and may be I could expect to extend the range
>of my wireless [AP] using [my notebook] configured as a
>"wireless bridge"?

router.

This sounds rather silly. YOu want to use a $2000 notebook to do what a $50
wireless router would do much better and much more easily. Why would you
want to do that?
Especially as you are apt to go wandering off with your notebook just as
the other person is getting settled in to do some surfing.




>Is this not what is meant by "bridging"? Have I put them
>all ok?

>The wireless [AP] is the gateway to the internet using the ESSID
>default and channel 6. The eth1 (put in managed mode) of my
>notebook associates to this [AP]. The other wireless iface ath0
>put in the master mode, same ESSID and channel, (or should

Different channel.

>I have used a different channel? Anyway, I've tried both),



>[her laptop] [my notebook]
> +-------------------+ 192.168.0.1
> | | DHCPD
>Do I "see" ----+-ath0 br0 eth1-+------- wireless [AP]
>the [AP] here | 192.168.0.200 | "default"
>via channel 4 +-------------------+ channel 6
>on another master managed 00:90:96:28:3E:EB
>laptop? "default" "default"
> channel 4 channel 6
> 00:11:F5:8D:8E:85 00:90:96:28:3E:EB
> (madwifi) (orinoco_cs)


># ifconfig ath0 0.0.0.0 down
># ifconfig eth1 0.0.0.0 down
># brctl addbr br0
># brctl addif br0 eth1
># brctl addif br0 ath0
># ifconfig br0 192.168.0.200 up
># ifconfig ath0 up
># ifconfig eth1 up
># brctl stp br0 on (Well, what's a "spanning tree"?)
># brctl show

>bridge name bridge id STP enabled interfaces
>br0 8000.0011f58d8e85 yes ath0
> eth1

># brctl showstp br0

>br0
> bridge id 8000.0011f58d8e85
> designated root 8000.0011f58d8e85
> root port 0 path cost
> 0
> max age 19.99 bridge max age
> 19.99
> hello time 1.99 bridge hello time
> 1.99
> forward delay 14.99 bridge forward delay
> 14.99
> ageing time 299.95
> hello timer 1.61 tcn timer
> 0.00
> topology change timer 0.00 gc timer
> 0.03
> flags


>ath0 (2)
> port id 8002 state
>disabled

>^^^^^^^^^^^^^
> #### Why is the ath0(2) "disabled" and how do I enable it?
> It is up and I do not understand these things ...

> designated root 8000.0011f58d8e85 path cost
> 100
> designated bridge 8000.0011f58d8e85 message age timer
> 0.00
> designated port 8002 forward delay timer
> 0.00
> designated cost 0 hold timer
> 0.00
> flags

>eth1 (1)
> port id 8001 state
>forwarding
> designated root 8000.0011f58d8e85 path cost
> 100
> designated bridge 8000.0011f58d8e85 message age timer
> 0.00
> designated port 8001 forward delay timer
> 0.00
> designated cost 0 hold timer
> 0.61
> flags


>`iwconfig` on [my notebook]:
>================================================= =

>ath0 IEEE 802.11b ESSID:"default"
> Mode:Master Frequency:2.427 GHz Access Point:
>00:11:F5:8D:8E:85
> Bit Rate:0 kb/s Tx-Power:18 dBm Sensitivity=0/3
> Retryff RTS thrff Fragment thrff
> Power Managementff
> Link Quality=56/94 Signal level=-39 dBm Noise level=-95 dBm
> Rx invalid nwid:2737 Rx invalid crypt:0 Rx invalid frag:0
> Tx excessive retries:598 Invalid misc:598 Missed beacon:4

>eth1 IEEE 802.11b ESSID:"default" Nickname:"HERMES I"
> Mode:Managed Frequency:2.427 GHz Access Point:
>00:11:F5:8D:8E:85
> Bit Rate:2 Mb/s Sensitivity:1/3
> Retry limit:4 RTS thrff Fragment thrff
> Power Managementff
> Link Quality=65/92 Signal level=-30 dBm Noise level=-95 dBm
> Rx invalid nwid:0 Rx invalid crypt:7823 Rx invalid frag:81
> Tx excessive retries:1 Invalid misc:0 Missed beacon:0

>br0 no wireless extensions.

>`ifconfig` on [my notebook]:
>================================================= =

>ath0 Link encap:Ethernet HWaddr 00:11:F5:8D:8E:85
> UP BROADCAST MULTICAST MTU:1500 Metric:1
> RX packets:779 errors:86953 dropped:0 overruns:0 frame:86953
> TX packets:462 errors:598 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:200
> RX bytes:206471 (201.6 KiB) TX bytes:61440 (60.0 KiB)
> Interrupt:11 Memory:df840000-df850000

>br0 Link encap:Ethernet HWaddr 00:11:F5:8D:8E:85
> inet addr:192.168.0.200 Bcast:192.168.0.255
>Mask:255.255.255.0
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:33 errors:0 dropped:0 overruns:0 frame:0
> TX packets:0 errors:0 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:0
> RX bytes:3162 (3.0 KiB) TX bytes:0 (0.0 b)

>eth1 Link encap:Ethernet HWaddr 00:02:2D:88:49:68
> UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1
> RX packets:12295 errors:6375 dropped:6375 overruns:0
>frame:6375
> TX packets:7 errors:1 dropped:0 overruns:0 carrier:0
> collisions:0 txqueuelen:1000
> RX bytes:2919469 (2.7 MiB) TX bytes:848 (848.0 b)
> Interrupt:3 Base address:0xb100

>Now I'd better put some explicit questions to reveal what
>I'm probably missing.

>1. Now that I have a dhcpd running on the [AP], if I go to
> [her laptop] I suppose I could talk to the [AP] via
> ath0 on channel 4, right? But nothing happened if
> I try to boot [her laptop] using a dhcp-client.
> No response is seen on [her laptop] upon DHCPDISCOVER.

>2. I have assigned an IP 192.168.0.200 to the br0 on
> [my notebook], since the [AP] is using 192.168.0.1.
> I then do

> route add default gw 192.168.0.1 dev br0

> and tried to ping the [AP] at 192.168.0.1. But nothing
> happended.

>3. The ath0 on [my notebook] does not seem to be forwarding
> packets. What's wrong here?

routing?


>4. I go to [my notebook] and changed the essid to "test".
> But this did not help.

>5. cat /proc/sys/net/ipv4/ip_forward
>1

>but I think this is irrelevant, isn't it?

No. You want the laptop to forward packets. YOu must tell it that you want
it to forward packets.


>6. ....

>Thanks in advance for any enlightening!

>>I want to "see" packets going through the layer 2 of the stack
>Why do you you want to see them?

experimenting and trying to understand what's going on.

>>on [my notebook] and may be I could expect to extend the range
>>of my wireless [AP] using [my notebook] configured as a
>>"wireless bridge"?
>
>router.
>
>This sounds rather silly. YOu want to use a $2000 notebook to do what
>a $50 wireless router would do much better and much more easily. Why
>would you want to do that?

Well, I was actually thinking of a low-level wireless repeater
for extending the range. A real repeater would be expensive I think.

And I've just got an old laptop for $10 two weeks ago. I guess
a linux running on such would be much more powerful and flexible
than what a "router" for $50 could provide.

>Especially as you are apt to go wandering off with your notebook just
>as the other person is getting settled in to do some surfing.

As for my $2000 one, yes, that would be a bit expensive for
a geostationary routing job. But I have actually used it while
wandering as an masquerading wireless AP for people who had
difficulty getting the signal for I carried with me a 12 dBi antenna

>>3. The ath0 on [my notebook] does not seem to be forwarding
>> packets. What's wrong here?
>
>routing?

This is what I'm wondering. I'm trying to learn more about
"bridging" transparently. And I guess it's sort of different
from "routing".

>>5. cat /proc/sys/net/ipv4/ip_forward
>>1
>>but I think this is irrelevant, isn't it?

>No. You want the laptop to forward packets. YOu must tell it that you want
>it to forward packets.

Tell whomelse? /proc/sys/net/ipv4/ip_forward is already 1.
I'm not sure at al, but I'm sure I'm missing something.
This is why I'm asking for help. Anybody ... ?
"Bridging" and "Routing" appears to me to happend at
different layers. Whereto should I categorize "ip_forward"
in the network stack? and bridging on earth?

thanks for the reply!

Are pockets coming in? Can the remote machine communicate with your laptop?
Can your laptop communicate with the wireless modem? Both need to be
working first. Then you have to make sure that the remote machine has your
machine's IP address as its gateway so it knows to send stuff to your
laptop. Then your laptop must know how to route packets it receives on to
its own gateway.
Then y ou have to make sure that your firewall allows stuff to go through.


(E-Mail Removed) writes:

>>>I want to "see" packets going through the layer 2 of the stack
>>Why do you you want to see them?

>experimenting and trying to understand what's going on.

>>>on [my notebook] and may be I could expect to extend the range
>>>of my wireless [AP] using [my notebook] configured as a
>>>"wireless bridge"?
>>
>>router.
>>
>>This sounds rather silly. YOu want to use a $2000 notebook to do what
>>a $50 wireless router would do much better and much more easily. Why
>>would you want to do that?

>Well, I was actually thinking of a low-level wireless repeater
>for extending the range. A real repeater would be expensive I think.

>And I've just got an old laptop for $10 two weeks ago. I guess
>a linux running on such would be much more powerful and flexible
>than what a "router" for $50 could provide.

>>Especially as you are apt to go wandering off with your notebook just
>>as the other person is getting settled in to do some surfing.

>As for my $2000 one, yes, that would be a bit expensive for
>a geostationary routing job. But I have actually used it while
>wandering as an masquerading wireless AP for people who had
>difficulty getting the signal for I carried with me a 12 dBi antenna

>>>3. The ath0 on [my notebook] does not seem to be forwarding
>>> packets. What's wrong here?
>>
>>routing?

>This is what I'm wondering. I'm trying to learn more about
>"bridging" transparently. And I guess it's sort of different
>from "routing".

>>>5. cat /proc/sys/net/ipv4/ip_forward
>>>1
>>>but I think this is irrelevant, isn't it?

>>No. You want the laptop to forward packets. YOu must tell it that you want
>>it to forward packets.

>Tell whomelse? /proc/sys/net/ipv4/ip_forward is already 1.
>I'm not sure at al, but I'm sure I'm missing something.
>This is why I'm asking for help. Anybody ... ?
>"Bridging" and "Routing" appears to me to happend at
>different layers. Whereto should I categorize "ip_forward"
>in the network stack? and bridging on earth?

>thanks for the reply!