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-   -   Broadcast in ad hoc networks (http://www.linuxquestions.org/questions/linux-networking-3/broadcast-in-ad-hoc-networks-248277/)

rickthemick 10-28-2004 03:57 AM

Broadcast in ad hoc networks
 
Hi all!
Problem: Broadcast packets are not delivered up to application from a different networkaddress.

Network setup: 2 hosts, 802.11 in ad hoc mode

[h1:10.0.3.2/24]--->packets(dst:255.255.255.255)--->[h2:10.0.1.1/24]

The problem is that h2 does not deliver any packets addressed to 255.255.255.255 (link local broadcast are not delivered either) from h1. My initilial thought was that this would work fine since both hosts are in ad hoc mode and should not care about the source IP adress but it seems that h2 does not deliver any pakets from h1 becuase of the "incorrect" source address (it does not belong to h2's network). I can se the packets comming in on h2 using Ethereal but they seems to be dropped.

Is it a incorrect understanding of ad hoc mode that it delivers any packet without considering the source address? (it seems so) If this is so, why does a ad hoc network consider the source address? (Seems odd to me) Is there any solution to this?

This set up works fine:
[h1:10.0.1.2/24]--->packets(255.255.255.255)--->[h2:10.0.1.1/24]
but I am limited to use the first setup with differnet network addresses.

Best Regards
Rickard

slide-rule 10-28-2004 05:20 PM

I'm probably totally missing the point of your problem, but if you need 10.0.2.* and 10.0.3.* to get traffic between them, oughtn't their netmasks be /16 and not /24 ? That they both work as 10.0.1.*/24 seems to be consistent to this. (Past this low-level observation, I'm unfamiliar with the vagaries of "ad-hoc", etc.)

rickthemick 10-29-2004 08:49 AM

Im probably totally missing the point of your problem, but if you need 10.0.2.* and 10.0.3.* to get traffic between them, oughtn't their netmasks be /16 and not /24 ?

Yes, thats true, it would work, but its not an option for me.

That they both work as 10.0.1.*/24 seems to be consistent to this. (Past this low-level bservation, I'm unfamiliar with the vagaries of "ad-hoc", etc.)

Also true. But it actually has nothing to do with Ad hoc networking I believe, the same would hold for standard ethernet cards connected through a hub.

Made a post where I claim that DHCP solves this problem, and made a question how. My thought is that the DHCP client set the source address to 0.0.0.0 which will make the packet to not be dropped at the IP-stack of the receiver.

My post about DHCP can be found here:
(changed topic so it will be seen by people who know DHCP well)
http://www.linuxquestions.org/questi...hreadid=248727


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