Reverse IP NAT to secondary IP address

[Nils Vogels]

"."@babolo.ru wrote:

>configure port with SNMP-server as 192.168.0.17/30 for example
>instead 192.168.2.1/24, and
>sysctl net.link.ether.inet.proxyall=1
>
>and configure SNMP-server as 192.168.0.18/24
>
>If you can change mask of SNMP-server, you can
>use 192.168.0/24 and 192.168.1/24 on gateway
>and 192.168.0/25 on  SNMP-server.
>
>No NAT is needed.
>  
>
I just tried this, but unfortunately, the same thing happens as with 
ipfilter:

The primary address of the interface ed0 on the gateway (the public 
adress) is used to forward the arp request.

Taken from a dump on the gateay, when attempting telnet:

Incoming on rl0:
03:35:05.867883 192.168.0.2.1511 > 192.168.2.2.23: S 
1377718084:1377718084(0) win 57344 <mss 1460> (DF) [tos 0x10]

Outgoing on ed0:
03:35:05.868333 195.0.0.1.15009 > 192.168.2.2.23: S 
1377718084:1377718084(0) win 57344 <mss 1460> (DF) [tos 0x10]

Since 195.0.0.1 (obviously obfuscated) does not fall within the subnet 
the 192.168.2.2 box is on, there will never be a reply from the 
192.168.2.2 box.

ARP proxying goes fine, on the WWW box, I can see the proxied reply 
coming from my gateway for the 192.168.1.1 address .....

Can anyone tell me, how I can make the box use the secondary address 
(alias) automatically for forwarding the telnet session?
Could it be that since the gateway is running many-to-one NAT as well, 
this is conflicting ?

Greetings,

Nils.