Date: Sat, 25 Oct 2003 21:04:23 +0200 From: Nils Vogels <nivo+sender+8eb026@yuckfou.org> To: freebsd-net@freebsd.org Subject: Reverse IP NAT to secondary IP address Message-ID: <3F9AC937.4070200@yuckfou.org>
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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 ? ;-)
Thanks,
Nils.
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