[Bridge] bridge wont forward when ip address changes

[Bridge] bridge wont forward when ip address changes

[Matt Richards]

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hello :)

I have been using the bridge utils for a long time now and its been very
good but there are a couple of issues that I came across when trying to
setup a wireless bridge...

Firstly I currently have a setup like the following ...

Computer A --- Wired Network --- linux box ---- wireless link ------
linux box ----- Wired Network --- Computer B

I have bridged the wireless interfaces and the wired interfaces together
on both of the linux box's and data can travel across the wireless
bridge without any trouble but if I attempt to change the IP addresses /
subnet of Computers A and B the bridges seem to stop forwarding packets
and no data get through at all, its like they aren't learning the new
addresses.

If I restart the 2 Linux boxes then everything starts flowing properly
again.

The 'Linux boxes' are a couple of Motorola Wireless Access points
running OpenWRT.

Does anybody know why this might be happening and what I might be able
to do about it?

The other issue is that the this bridge setup doesn't seem to forward
any NetBIOS traffic, however, i'm not too worried about this its more of
just bring curious.

Thanks for your help,

Matty.


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Re: [Bridge] bridge wont forward when ip address changes

[Matt Richards]

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Andy Gospodarek wrote:
> On 2/10/07, Matt Richards <matt@mattstone.net> wrote:
>> hello :)
>>
>> I have been using the bridge utils for a long time now and its been very
>> good but there are a couple of issues that I came across when trying to
>> setup a wireless bridge...
>>
>> Firstly I currently have a setup like the following ...
>>
>> Computer A --- Wired Network --- linux box ---- wireless link ------
>> linux box ----- Wired Network --- Computer B
>>
>> I have bridged the wireless interfaces and the wired interfaces together
>> on both of the linux box's and data can travel across the wireless
>> bridge without any trouble but if I attempt to change the IP addresses /
>> subnet of Computers A and B the bridges seem to stop forwarding packets
>> and no data get through at all, its like they aren't learning the new
>> addresses.
>>
>> If I restart the 2 Linux boxes then everything starts flowing properly
>> again.
>>
>> The 'Linux boxes' are a couple of Motorola Wireless Access points
>> running OpenWRT.
>>
>> Does anybody know why this might be happening and what I might be able
>> to do about it?
>>
>
> I wonder if this is ARP related?  I've noticed some interesting
> behavior when bridging wired and wireless devices.  Have you noticed
> that you can communicate after the IP switch if you send a gratuitous
> ARP from any of the wireless devices?
>
hello,
no i haven't tried tried that, i did notice that if i try to make a
computer talk to another device after the ip change the arp table would
contain the IP with an invalid state and no mac address or a mac address
of all F's i think it was.

Sending arp packets wouldn't be a solution as this will be used in a
computer lab to connect sockets that are in parts of the room where its
not easy to run cables and therefore wouldn't be ideal for people to use
when learning about network operating systems.

One thing I have just thought of, while reading an email from the
openvpn mailing list, is that if i setup an openvpn tunnel with tap
interfaces over the wireless link and bridge the switches to the tap
interface then the problem should go away if it is to do with the
wireless interfaces.

Is a little weird tho, I had to lower to mtu to get the devices to ping
in the first place.

Matty.



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