Reverse IP NAT to secondary IP address
"." at babolo.ru
"." at babolo.ru
Sat Oct 25 17:32:16 PDT 2003
[ Charset ISO-8859-1 unsupported, converting... ]
> Hi there!
>
> I'm trying to solve a situation that I have with a device which needs
> SNMP polling, but is not normally reachable to the outside world,
> because it cannot install a default gateway.
>
> In short, a situation scetch:
>
>
>
>
> SNMP-server (192.168.2.2/24)
>
> -----------
> +------------+ +-------------+
> |
> | WWW |--------------------| Gateway | --------------+
> +------------+
> +-------------+ |
> 192.168.0.2/24 192.168.0.1 IP: 195.x.x.x.x
> \-----> Internet (0.0.0.0/0)
> (rl0) Alias:
> 192.168.2.1
>
> (ed0)
>
> Now what I am trying to do is get statistics from the SNMP-server into
> the WWW box, but I am stuck on the following:
>
> WWW is a FreeBSD-4.8 box.
> Gateway is a FreeBSD-4.8 box with IP Filter
> Since the SNMP-server does not have a default route, the traffic needs
> to originate from an IP address within the same subnet as the Gateway.
> To that end, I have added an alias IP of 192.168.2.1 to the gateway.
> When I run an snmpwalk from the gateway all goes fine.
>
> Since the traffic is coming from WWW and heading through the Gateway,
> which does not bridge, I have to perform some form of NATting in the
> gateway.
>
> I've been searching and attempting various redirects and map entries,
> and am now stuck at:
>
> map rl0 from 192.168.0.0/24 to 192.168.2.0/24 port = 161 -> 192.168.2.1/32
>
> I think I'm close .. can someone give me the final hint ? ;-)
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.
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