topic help to configure a DMZ and NAT in General Topics

help to configure a DMZ and NAT

assona — Fri, 03 Aug 2012 12:35:55 GMT

hi,

i need a little help to configure a DMZ. here is our situation:

interfaces

ethernet1/1 - 1.1.1.1 (public - NAT clients)

ethernet1/1.1 - 1.1.1.2 (public - NAT DMZ)

ethernet1/1.2 - 1.1.1.3 (public)

ethernet1/6 - 10.10.30.1 (DMZ)

ethernet1/8 - 10.10.20.1 (clients)

routing

default route 0.0.0.0 -> 1.1.1.1 (works!)

NAT

clientOut dynamic-ip-and-port ethernet1/1 1.1.1.1 (works)

DMZIn dest address translation 10.10.30.20 (works)

question

what can i do that all DMZ hosts use the interface ethernet1/1.1 for outside (untrust) communication. i tried policy based forwarding, but without success.

thanks

tom

Re: help to configure a DMZ and NAT

UKRB — Mon, 06 Aug 2012 15:38:33 GMT

Hi Tom,

I'm a bit lost as to why you have all the sub interfaces on the external side? I have done something similar recently where I wanted one network behind an interface (essentially a guest network) to go out behind a different public IP but I just defined the IP as an object and then specified the NAT rule to use that object as the new source address on it's way out.

Also, your route suggests the default router out is one of your own IPs (1.1.1.1 being on eth1/1) this would just send traffic back to the firewalls so I can't see how that works? Perhaps I'm missing something?

UKRB

Re: help to configure a DMZ and NAT

bvandivier — Tue, 02 Oct 2012 18:53:01 GMT

UKRB is correct, a layer 3 sub-interface with the IP address you wish to NAT your DMZ network behind (hide NAT or dynamic NAT) is not required.

Simply creating a "source NAT" policy rule translating your 10.10.30.x DMZ network to the public ip 1.1.1.2 should be sufficient. For example:

dmz-nat {

source-translation {

dynamic-ip-and-port {

translated-address 1.1.1.2/32;

}

to untrust;

from dmz;

source 10.10.30.0/24;

destination any;

service any;

to-interface any;

}