How to make routing no NAT

Hello i have 3 link of 3 ethernet card

eth1 GW ISP1
eth2 ISP1 routed on at provider routers

eth3 GW: ISP2

eth1 and eth2 is from ISP1
and eth3 ISP2
now ip calss its routed on by ISP1
i use eth1 and eth3 for NAT ( using multi wan connection and i set to Active backup.

my problem is on ip classes i want to use ip from this class on other server (mail server, hosting server, etc: example with gw netmask is mail server and netmask in hosting server).
but my nethserver make NAT for this class on eth1 or eth3, as well as

single way to use the clase is behind NAT 1:1 with ip aliases added on eth1 (ex: eth1:1, eth1:2 ) forward to ip form class

PLEASE HELP ME to use this class in routing mode not NAT mode.


Hello Friend,

You have your ISP hardware which has 2 network ports, and you have assigned 2 IP? and a second ISP where you assign only 1 IP, right?

You’ll use to NethServer as hosting and mail server?

No, one single ports my class /25 its not opperable if not put on interface eht1 connected IP
i can put on the some interface ip from ISP1 like that.

eth1 have and
eth1:1 this ip i want to use at gateway for other server(mail server and hosting server).
with eth2 i connect on switch wher i have connected my server (mail server and hosting server, etc form class
no i dont use nethserver for hosting and mail server.

Hi Dan,

Can you make a sketch with your configuration (ISP router -> NethServer)?
Do you have from your ISP only a MC or a router (or MC and router)?


From ISP1 i have MC with 1 ethernet port

at short for ip classess i want to bypass firewall

This is a Vlan?

You have your settings like this?

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@zotinas If you do ping responds to the request?

If you use you access NethServer?

Something like that is your settings?

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Yes respond to ping and i made it even ip address with gw to respond to ping form external connection, but when I acces internet from my ip address (, seems that is going to internet with NAT address ( ISP1 or ISP2). I use active backup internet connection.

yes the configuration is like the above screenshot

You want to assign to a station that Alias as wan? or you want to access from the Internet via alias?

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Hi Dan,

Please see the attached picture.
Is this sketch correct?
If yes, do you want NAT 1:1 from ISP1 to SW1 and port forwarding from ISP2 to SW2?


@zotinas seeing the graph of @GG_jr mail server and web server must use the ISPx (x=1 or 2) is correct?

Considering that each service is being used in different hardware


I read again and I think this is the correct sketch (please see below).

And I think Dan want to use ISP1 and ISP2 as Active Backup for eth0 (GREEN) and for eth2 (ORANGE).
The problem is that he has his subnet routed only by ISP1 and not also by ISP2.
In this case, when ISP1 is down, the servers from eth2 will not be seen from Internet.
But can access the Internet from eth0 and from eth2
Only If I understand well.


that’s right @GG_jr

multiwan should use balanced mode

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Or BGP between ISP1 and ISP2.
Dan’s subnet must be routed by ISP1 and also by ISP2.

I had the same situation and BGP is the best solution.

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My situation (the short version).

Hello, that is the correct sketch. For the mail server and web server, ISP2 give me ip from a cisco router, and on each server (mail and hosting server), i use a second network card with ip form IPS2 and my backup for this server is from DNS zone.
My problem is with isp1 which gives me ip directly connected ( and ip class on the same port. And i want this class ( the server was straight forward bypass the firewall from nethserver.

for this solution requires its own AS and its own ip classes form RIPE. Now this is complicated and the costs are significantly higher.
Thanks anyway.

Indeed, I have an AS number and the IP Public subnet is from RIPE.

You’re right!