On Tue, Dec 03, 2002 at 06:34:00PM +0100, virdzek, roman wrote:
> hi all,
>
> i have one little problem,and i can't find answer.
>
> PC1
>
> eth1 eth2
> 10.0.0.1/8 10.0.0.2/8
> | 10.0.0.3/8 secondary
> | |
> | |
> | |
> |
> switch -------------
> |
> |
> |
> eth1
> 10.0.0.10/8
> PC2
> (default route 10.0.0.2)
>
> i have set arp_filter=1,
> and 2 ip tables , A and B
>
> table A:
> 10.0.0.0/8 dev eth1 scope link
> table B:
> 10.0.0.0/8 dev eth2 scope link
>
> and ip rule:
> ... from 10.0.0.1 lookup A
> ... from 10.0.0.2 lookup B
> .
> .
>
>
> ping PC2 -> 10.0.0.1 ...ok answer come from eth1
> ping PC2 -> 10.0.0.2 ...ok answer come from eth2
>
> but
> ping PC2 -> 10.0.0.3(secondary) ... wrong answer come from eth1 !
> PC1 answer on arp question "who has 10.0.0.3", "10.0.0.3 is at eth1"
>
> If I set arp_filter=0,
> and set hidden = 1 :
> ping PC2 -> 10.0.0.3(secondary) ... no answer
>
>
> what i make wrong?
Well, some people say this behaviour is correct wrt the rfc. I wont go into
that discussion.
After searching for a long time, I found this way to solve the problem:
1) make sure there are no wrong ARP replies:
echo 1 > /proc/sys/net/ipv4/conf/$DEVICE/arp_filter
2) make sure the packets are sent from the correct interface:
Turn advanced routing on in the kernel.
CONFIG_IP_ADVANCED_ROUTER=y
For every REAL interface (not alias), try:
(the variables should be clear, add entries to /etc/iproute2/rt_tables for
every device, to make configuration easier to read)
ip route add ${NET} dev ${DEVICE} scope link table ${DEVICE}
ip route add default via ${GATEWAY} dev ${DEVICE} table ${DEVICE}
ip rule add from ${ADDR} table ${DEVICE}
For every ALIAS do
ip rule add from ${IP} table ${TABLE}
This setup means that every packet is routed based on the source address.
I've used it for some time now, and it works just fine.
I hope this helps.
Greetings,
Ivo De Decker
P.S. Maybe this could be documented in the LARTC.
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