Incorrect route interface

[Grzegorz Junka]

On 12/03/2018 18:04, Rodney W. Grimes wrote:
>> On 11/03/2018 20:57, Marek Zarychta wrote:
>>> On Sun, Mar 11, 2018 at 05:46:52PM +0000, Grzegorz Junka wrote:
>>>> On 11/03/2018 06:04, Eugene Grosbein wrote:
>>>>> 11.03.2018 7:01, Grzegorz Junka wrote:
>>>>>
>>>>>>> Just do not assign addresses from same network 10.20.0.0/16 to different network interfaces
>>>>>>> and you will be fine. Assign them all to right interface:
>>>>>>>
>>>>>>> ifconfig_em0="inet 10.20.2.14 netmask 255.255.0.0"
>>>>>>> ifconfig_em0_alias0="inet 10.20.2.15/32"
>>>>>>> ifconfig_igb0_alias0="inet 10.20.2.16/32"
>>>>> Interfaces meant to be all equal, last line should be:
>>>>>
>>>>> ifconfig_em0_alias1="inet 10.20.2.16/32"
>>>>>
>>>> OK, I see. So this is in case I want many IPs assigned to the same
>>>> interface. What if I want one IP assigned to multiple interfaces (i.e.
>>>> so that the additional igb0-3 effectively work as a 4-port switch)?
>>>>
>>> Please consider bonding all NICs as one bridge(4) interface. Then
>>> multiple IPs could be assigned to such interface.
>>>
>> Many thanks Eugene and Marek for your suggestions. I will now need to
>> decide if I want to fragment the network into subnets or bridge the
>> interfaces.
>> GregJ
> I believe some of the problem you are experincing is addressed
> in this differential:
> https://reviews.freebsd.org/D14547
>
> Your original configuration was(is) valid, just not common,
> and I have not seen this done in more than a decade, but it
> seems as if rstone@ also has someone doing this "multiple IP's
> into same subnet on seperate interfaces".
>

Thanks for the link. That's interesting. According to this post that 
configuration shouldn't be valid:

https://forums.freenas.org/index.php?threads/multiple-network-interfaces-on-a-single-subnet.20204/