Bridge problems

My home network consists of a Linux packet-filtering router serving a
handful of Win2K & WinXP boxes and two laptops (not diagrammed below),
connected within two Class C subnets: 192.168.1.0\24 (802.11b) &
192.168.2.0\24 (10BT).

Here's a simple network diagram: (view using Courier font or equiv.)

wlan0 eth0

+---------+ +---------+------+ +-------+-------+
| | | | | | | |
cable_modem wireless_router box_1 Linux_router box_2 printer

I would like to bridge wlan0 & eth0, merging the two subnets. All addresses
on wlan0 & eth0 are static -- the wireless router is instructed to recognize
machines by MAC ID. I've loaded the newer bridge module (bridge.o) per the
HOWTO, and hosts on the two subnets could see each other, but box_2 could
not see the wireless_router.

Assuming this configuration is workable, how should routing work: should
box_2's default gateway be the wireless router's IP, or that of the Linux
router? I would expect it to be the wireless router, but box_2 cannot see
it. The bridge doesn't appear to be completely transparent -- do I need
help from iptables? Please note that the Linux router will also be a host
on the merged network -- does this make a difference?

I suspect I haven't given enough information, but this is all I have time to
write, for the moment. Any ideas or suggestions would be greatly
appreciated.

Thanks,

Eric Adamson
Lansing, Michigan

Just a quick note -- I describe my network as featuring a Linux
packet-filtering router, which is not entirely accurate. Iptables was not
active during bridging experiments. Well, iptables may have been active,
but all default chain policies were set to ACCEPT, and all rules were
flushed.

Eric



"Eric Adamson" <(E-Mail Removed)> wrote in message
news:8WO6e.6441$_(E-Mail Removed)...
> My home network consists of a Linux packet-filtering router serving a
> handful of Win2K & WinXP boxes and two laptops (not diagrammed below),
> connected within two Class C subnets: 192.168.1.0\24 (802.11b) &
> 192.168.2.0\24 (10BT).
>
> Here's a simple network diagram: (view using Courier font or equiv.)
>
> wlan0 eth0
>
> +---------+ +---------+------+ +-------+-------+
> | | | | | | | |
> cable_modem wireless_router box_1 Linux_router box_2 printer
>
> I would like to bridge wlan0 & eth0, merging the two subnets. All
addresses
> on wlan0 & eth0 are static -- the wireless router is instructed to
recognize
> machines by MAC ID. I've loaded the newer bridge module (bridge.o) per
the
> HOWTO, and hosts on the two subnets could see each other, but box_2 could
> not see the wireless_router.
>
> Assuming this configuration is workable, how should routing work: should
> box_2's default gateway be the wireless router's IP, or that of the Linux
> router? I would expect it to be the wireless router, but box_2 cannot see
> it. The bridge doesn't appear to be completely transparent -- do I need
> help from iptables? Please note that the Linux router will also be a host
> on the merged network -- does this make a difference?
>
> I suspect I haven't given enough information, but this is all I have time
to
> write, for the moment. Any ideas or suggestions would be greatly
> appreciated.
>
> Thanks,
>
> Eric Adamson
> Lansing, Michigan
>
>

On 2005-04-12, Eric Adamson <(E-Mail Removed)> wrote:
> My home network consists of a Linux packet-filtering router serving a
> handful of Win2K & WinXP boxes and two laptops (not diagrammed below),
> connected within two Class C subnets: 192.168.1.0\24 (802.11b) &
> 192.168.2.0\24 (10BT).
>
> Here's a simple network diagram: (view using Courier font or equiv.)
>
> wlan0 eth0
>
> +---------+ +---------+------+ +-------+-------+
> | | | | | | | |
> cable_modem wireless_router box_1 Linux_router box_2 printer
>
> I would like to bridge wlan0 & eth0, merging the two subnets. All addresses
> on wlan0 & eth0 are static -- the wireless router is instructed to recognize
> machines by MAC ID. I've loaded the newer bridge module (bridge.o) per the
> HOWTO, and hosts on the two subnets could see each other, but box_2 could
> not see the wireless_router.

According to BRIDGE-STP-HOWTO:
"A bridge is a device that separates two or more network segments
within one logical network (e.g. a single IP-subnet)."

Forwarding should be enough, but it all would be simpler with one
logical network. If you must have two:
- on linux router you should have forwarding enabled,
- on linux router set wireless router as default gateway and
check if routes to 192.168.1.0/24 and 192.168.2.0/24 are set,
- on box_2 set linux router as default gateway,
- on wireless router set route to 192.168.2.0/24 with linux
router as gateway; if it's not possible, you can set SNAT on linux
router for connections from 192.168.2.0/24.

Jarek Poplawski

Eric Adamson <(E-Mail Removed)> wrote:
> I would like to bridge wlan0 & eth0, merging the two subnets

Unless you've got true native Linux drivers for your wireless card (e.g.
prism?) you won't be able to bridge to it.

Chris