2 LANs on one network

I have an existing subnet (LAN1) 192.168.201.x (gateway: getting addressing from an 2011 SBS server (  I need to to add a second subnet (LAN2) on the network (192.168.173.x) with at least one computer on the network at this time ( sharing the same gateway (  Routing on the 192.168.201.x network is done via the SBS server.  Routing for the 192.168.173.x network gets it's addressing off of a Westermo Lynx L110/L210 series industrial router.  When working correctly I should be able to ping this second network from the first and visa-versa and share resources between the 2 networks (network shares, etc).  How can I do this?

Thank you!

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Brad GrouxSenior Manager (Wintel Engineering)Commented:
If they are Windows computers on two different AD domains you could set up a trust. If they aren't all on domains then you could utilize DNS, the problem would be having to maintain two different DNS infrastructures as changes are made in the environment.
Fred MarshallPrincipalCommented:
Let's see if I have this right:

2011 SBS server (
  Provides DHCP service to on LAN1.
  Gateway is on that same LAN.

You want:
LAN2 using subnet
DHCP service from Westermo Lynx L110/L210
Gateway to be

A very simple arrangement that could begin to meet your requirements would be to;
Cascade the Westermo "switch" with the subnet and using a static IP address in that range and with
(In my language, this would be the WAN interface).
Per the manual:
An interface can be configured to retrieve its IP settings dynamically via DHCP
(VLAN interfaces) or IPCP (PPP interfaces). In addition to interface settings such
as IP address and netmask, the switch can also acquire general network settings
such as default gateway and DNS server(s) from the DHCP server, or via PPP.
So, that's what I'm referring to here.
Provide DHCP service from the Westermo to a LAN with subnet.

This does everything except route packets between the subnets.
But, because the gateway is on the existing subnet, packets destined from the new subnet to the old subnet should be forwarded by the Westermo.  The manual says:
It is also possible to configure additional, static IP routes
So, either it will "just work" or you might need to add a route: > 192.168.201.xxx where xxx is the "WAN" port address .. but probably not.

To get packets back into, you will need a route in the gateway device: > 192.168.201.xxx

The Westermo is a little different in terms of how it refers to things.  While it's a "switch" in name, it has a lot of router capabilities.  Perhaps the best way to think of it is that it's a non-NAT router that will interface between two subnets.  I think all of what I've said above will fit into that context.  
As I briefly read the manual, it appears you would set up a VLAN for the upstream port and a VLAN for the downstream port(s) with DHCP reception (or static IP) on the upstream port and DHCP service provided on the downstream port(s).

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