Hello, On my /proc/sys/net/ipv4/conf I found arp_filter = 0. I changed this parameter directly in devinet.c and than recompiled the kernel.
Now arp_filter = 1 and there's only one answer to the ARP request! Thanks for the precious support... Luigi -----Messaggio originale----- Da: Stefano Babic [mailto:[email protected]] Inviato: mercoledì 17 novembre 2010 20.02 A: Luigi Rizzi Cc: 'Detlev Zundel'; 'Stefano Babic'; [email protected] Oggetto: Re: R: [ELDK] ARP Messages On 11/17/2010 05:49 PM, Luigi Rizzi wrote: > Hi Detlev,Stefano, > > yes I really appreciate this mailing list! (and sorry if some questions are > not too much ELDK related...) Well, you can probably find more specific answers checking in the corresponding ML. > Well, Module interfaces and sniffer are connected to the same Ethernet HUB, > in this way the sniffer can see every input/output packet from Eth1 and > Eth2. > So, All my test were done NOT on two physical separated network. > > Stefano, are you sure about the fact that is not allowed to have both > interfaces sharing the same segment? Probably "not allowed" was not the best explanation. But think about what happens if each network has its own DHCP server. The main problem is that broadcast messages are *not* routed, but because the two networks are connected together, both networks receive the same packets.And there could be a lot of side effects. What you see is called "arp flux", or something like this - I think is reported in one book I read, but you can easy find in internet. I tried with google and I see there is a lot of results. The behavior you reported *should* be correct and conform to standards (well, to be sure you have to check in the related RFCs documents...) > > Anyway, there's in your opinion a workaround to avoid this double ARP > packet? Well, I have no idea if there was something for 2.4 Kernel, is too old to remember, but...surprise ! There is a setup for 2.4 kernel, too. Check Documentation/networking/ip-sysctl.txt and search for arp_filter. It should be your friend: arp_filter - BOOLEAN 1 - Allows you to have multiple network interfaces on the same subnet, and have the ARPs for each interface be answered based on whether or not the kernel would route a packet from the ARP'd IP out that interface (therefore you must use source based routing for this to work). In other words it allows control of which cards (usually 1) will respond to an arp request. 0 - (default) The kernel can respond to arp requests with addresses from other interfaces. This may seem wrong but it usually makes sense, because it increases the chance of successful communication. IP addresses are owned by the complete host on Linux, not by particular interfaces. Only for more complex setups like load- balancing, does this behaviour cause problems. arp_filter for the interface will be enabled if at least one of conf/{all,interface}/arp_filter is set to TRUE, it will be disabled otherwise So you can try setting arp_filter to 1, and test again. Best regards, Stefano Babic -- ===================================================================== DENX Software Engineering GmbH, MD: Wolfgang Denk & Detlev Zundel HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: +49-8142-66989-0 Fax: +49-8142-66989-80 Email: [email protected] ===================================================================== _______________________________________________ eldk mailing list [email protected] http://lists.denx.de/mailman/listinfo/eldk
