Re: [lwip-users] No ARP reply by using two NICs

[Stefan Lankes]

Yeah, in the meantime I thought about the problem and learnt the differences 
between layer 2 and 3. :-)

Stefan

Am 16.08.2012 um 10:43 schrieb Sylvain Rochet <address@hidden>:

> Hi,
> 
> On Tue, Aug 14, 2012 at 03:01:59PM +0200, Stefan Lankes wrote:
>> Hi LwIP users,
>> 
>> I have an ARP problem and I am not sure, if this a problem of LwIP.
>> 
>> In our academic operating system, we use LwIP 1.4.0 as TCP/IP stack. 
>> My test system posses two network devices and each device belongs to 
>> its own subnet. I enabled IP forwarding to transfer IP packets between 
>> the subnets and it seems to work.
>> 
>> However, if a member of subnet A broadcasts an ARP request to 
>> determine the physical address of a member of subnet B, our system 
>> does not forward these broadcasts to subnet B. LwIP drops the requests 
>> with the message "ARP request was not for us."
>> 
>> Is this behavior correct?
> 
> With your wanted behavior, a broadcast Ethernet frame sent to a router 
> connected to the global IP space would be received by all IP equipments 
> connected, which is about billions of systems. And you are considering 
> the whole Internet is only made of Ethernet links, which is false. Maybe 
> you have to learn the difference between layer 2 and layer 3.
> 
> Sylvain
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