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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