Linux Ethernet Bridging - Apr 2007 - [Bridge] strange networking behaviour with a bridge in game

On 4/5/07, Peter Warasin <peter@endian.it> wrote:
> hi list
>
> I have a strange problem here. Maybe it is normal behavior and i search
> within the wrong direction. Probably someone here can give me a hint.
>
> I have a device (rhel4 kernel 2.6.9) with 3 interfaces. 2 interfaces
> (eth0, eth2) are bridged together (br0) and the bridge device has an ip
> address assigned (192.168.11.15).
> Another interface (eth1) has assigned 10.7.0.10.
>
>
> So far so good. Everything is working well if traffic passes from
> 192.168.11.0/24 out to 10.7.0.0/24 if both networks are on different
> switches.
>
> The thing begins to become strange if both eth0 and eth1 are connected
> on the same switch (eth2 is not connected). So i have both subnets on
> the same switch (for testing purposes).
> If i then would like to access 192.168.11.15, packets reach the device
> through the interface eth1 instead of eth0/br0, which in fact is wrong.
> The arp table on the client shows this also. 192.168.11.15 is assigned
> to the mac adress of the interface eth1.
>
> Needless to say that this happens only from time to time. If i cleanup
> the arp table sometimes it went alright.
>
> What's wrong with my installation?
>
> Thank you in advance!
>
> peter
>
>
> --
> :: e n d i a n
> :: open source - open minds
>
> :: peter warasin
> :: http://www.endian.com   :: peter@endian.com
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> Bridge@lists.linux-foundation.org
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>

Check out the ip sysctl/proc arp_ignore

net.ipv4.conf.tun0.arp_ignore = 0
net.ipv4.conf.eth0.arp_ignore = 0
net.ipv4.conf.lo.arp_ignore = 0
net.ipv4.conf.default.arp_ignore = 0
net.ipv4.conf.all.arp_ignore = 0

or

/proc/sys/net/ipv4/conf/tun0/arp_ignore
/proc/sys/net/ipv4/conf/eth0/arp_ignore
/proc/sys/net/ipv4/conf/lo/arp_ignore
/proc/sys/net/ipv4/conf/default/arp_ignore
/proc/sys/net/ipv4/conf/all/arp_ignore


arp_ignore - INTEGER
        Define different modes for sending replies in response to
        received ARP requests that resolve local target IP addresses:
        0 - (default): reply for any local target IP address, configured
        on any interface
        1 - reply only if the target IP address is local address
        configured on the incoming interface
        2 - reply only if the target IP address is local address
        configured on the incoming interface and both with the
        sender's IP address are part from same subnet on this interface
        3 - do not reply for local addresses configured with scope host,
        only resolutions for global and link addresses are replied
        4-7 - reserved
        8 - do not reply for all local addresses

        The max value from conf/{all,interface}/arp_ignore is used
        when ARP request is received on the {interface}

hi list

I have a strange problem here. Maybe it is normal behavior and i search
within the wrong direction. Probably someone here can give me a hint.

I have a device (rhel4 kernel 2.6.9) with 3 interfaces. 2 interfaces
(eth0, eth2) are bridged together (br0) and the bridge device has an ip
address assigned (192.168.11.15).
Another interface (eth1) has assigned 10.7.0.10.


So far so good. Everything is working well if traffic passes from
192.168.11.0/24 out to 10.7.0.0/24 if both networks are on different
switches.

The thing begins to become strange if both eth0 and eth1 are connected
on the same switch (eth2 is not connected). So i have both subnets on
the same switch (for testing purposes).
If i then would like to access 192.168.11.15, packets reach the device
through the interface eth1 instead of eth0/br0, which in fact is wrong.
The arp table on the client shows this also. 192.168.11.15 is assigned
to the mac adress of the interface eth1.

Needless to say that this happens only from time to time. If i cleanup
the arp table sometimes it went alright.

What's wrong with my installation?

Thank you in advance!

peter


-- 
:: e n d i a n
:: open source - open minds

:: peter warasin
:: http://www.endian.com   :: peter@endian.com