arp_filter=0 is the default, so I'm sure I've tested it with this
setting. I think I've tested with arp_ignore=0 too, although with
trying so many different combinations, I might've missed it out. I'll
keep this in mind when testing next.

Thanks.

On Mon, Jan 19, 2015 at 10:14 PM, Dave Tian <[email protected]> wrote:
> What about arp_filter=0 && arp_ignore=0?
>
> -daveti
>> On Jan 19, 2015, at 9:14 PM, Mandeep Sandhu <[email protected]> 
>> wrote:
>>
>> Here's how my current setup looks like:
>>
>> $ ifconfig eth4
>> eth4      Link encap:Ethernet  HWaddr 74:fe:48:04:e7:eb
>>          inet addr:192.168.1.1  Bcast:192.168.1.255  Mask:255.255.255.0
>> ...
>> $
>> ifconfig eth5
>> eth5      Link encap:Ethernet  HWaddr 74:fe:48:04:e7:e6
>>          inet addr:192.168.1.2  Bcast:192.168.1.255  Mask:255.255.255.0
>> ...
>>
>> $ ip route show
>> default via 192.168.1.2 dev eth4
>> 192.168.1.0/24 dev eth4  proto kernel  scope link  src 192.168.1.1
>> 192.168.1.0/24 dev eth5  proto kernel  scope link  src 192.168.1.2
>>
>> I've deliberately added a default gateway to 192.168.1.2 (so that the
>> ARP response is routed back through it).
>>
>> $ip neigh show
>>
>> (there's no neighbor entries)
>>
>> cat /proc/sys/net/ipv4/conf/all/rp_filter
>> 0
>> cat /proc/sys/net/ipv4/conf/all/arp_filter
>> 1
>> cat /proc/sys/net/ipv4/conf/eth4/rp_filter
>> 0
>> cat /proc/sys/net/ipv4/conf/eth4/arp_filter
>> 1
>> cat /proc/sys/net/ipv4/conf/eth5/rp_filter
>> 0
>> cat /proc/sys/net/ipv4/conf/eth5/arp_filter
>> 1
>>
>> Even with these settings, ARP for 192.168.1.2, via eth4 (192.168.1.1)
>> interface fails.
>>
>>
>>
>>
>> On Mon, Jan 19, 2015 at 5:31 PM, Mandeep Sandhu
>> <[email protected]> wrote:
>>>> You'd mentioned earlier that your setup was this:
>>>>
>>>> xeth0 - 192.168.2.1
>>>> xeth2 - 192.168.2.2
>>>>
>>>> That looks to me like two network interfaces on the same subnet, though 
>>>> that's my guess since you don't show the prefix lengths. I'm guessing the 
>>>> subnet on both is 192.168.2/24.
>>>
>>> Correct. Netmask is /24.
>>>
>>>>
>>>> Unless things have changed since the last time I looked into this, for 
>>>> IPv4 Linux implements what's referred to as the "weak" address binding 
>>>> model where IP addresses are considered to belong to the host not the 
>>>> interface. That means your host may be transmitting an ARP response, but 
>>>> not out the interface you expect, particularly if in fact you have the 
>>>> same subnet assigned to more than one interface.
>>>>
>>>> You might want to tcpdump on all interfaces when you do this.
>>>
>>> I actually did that (after some googling) but there's no ARP response
>>> being transmitted out of either of the interfaces. As I mentioned
>>> before, this problem happens even with regular ethernet interfaces and
>>> not specifically with my custom hardware related ones, so looks like a
>>> routing (mis)configuration issue.
>>>
>>>>
>>>> Also, you might want to include the output of the following in future 
>>>> posts:
>>>>
>>>> ip addr show
>>>> ip route show
>>>> ip neigh show
>>>
>>> I'll now test with 2 "regular" ethernet interfaces on my test machine
>>> (eth0,eth1) and send the o/p of these commands.
>>>
>>> Thanks!
>>>
>>>>
>>>> Jeff Haran
>>>>
>>
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>

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