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Currently I am testing a network and it almost does everything that I want it to do. Just one final step is missing and I am wondering if it is even possible in the current setup.

I am using a router-on-a-stick with different VLANs. All (except for one) of these VLANS have a gateway. In the VLAN with no NAT gateway there are some devices that I would like to reach from the other VLANs.

See network layout:Network layout

So the devices 1-18 that are in VLAN 200 I would like to be available on 192.168.200.X so I can reach these devices from VLAN10, VLAN20 etc. Currently I have this setup on my desk and I am unable to ping these devices. When the VLAN gateway is set I can ping these devices. Now I would like a solution where I do not have to set the gateway for the VLAN, but still can reach these from VLAN10, 20 etc.

Devices in VLAN 10 can already reach devices in VLAN 20 by using 192.168.20.X and vica versa.

The router is setup with VLAN:

VLAN 10 ip 192.168.10.1

VLAN 20 ip 192.168.20.1

VLAN 100 ip 192.168.100.1

VLAN 200 ip 192.168.200.1

Just the VLAN 200 NAT Gateway 192.168.200.1 -> 172.16.11.1 is missing

1 Answer 1

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Since you're using ambiguous addressing and overlapping subnets, NAT is a must.

Acessing a device that requires translating the destination address requires destination NAT (reverse NAT, port forwarding).

In reverse, if addressing isn't ambiguous but transparent (or can be made transparent) between any two nodes, then you would never use a hack like NAT.

Of course, in a proper network design you would never use any address translation, just transparent routing. You'd only have a single translating gateway between your privately addressed LAN and the publicly addressed WAN. If there's no ultimate requirement mandating duplicate addressing, just renumber properly and use a layer-3 switch as gateway between all your VLANs. Enjoy the speed and the lack of complications.

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