Subnet routing problem

Question

I am attempting to configure a temporary network for a client. I'm having some problems with getting the devices to communicate. Here are the details of the current configuration. *Note: I cannot change the IP scheme of the current configuration, forcing me to resort to some crafty routing pattern (if possible)

What I have so far:

Gateway to WAN (G1) - 192.168.254.0/24

RV130 VPN Gateway/Router in Router mode (R1) - WAN: 192.168.254.200/24,LAN: 10.55.142.1/24

Cisco Managed Switch (SW1) - 172.16.6.1/16

Control Logix PLC (PLC1) - 172.16.6.2/16

Control PC (PC1) - 172.16.100.10/16

What I need to do is create a PPTP vpn connection on the RV130 (R1) accessible from the outside that can access both (PLC1) and (PC1).

Unfortunately, the RV130 (R1) can only support a network with a cidr value of 24 or greater.

How I have them connected is as follows:

(G1:LAN) <-> (R1:WAN)-(R1:LAN1) <-> (SW1:Port4)-(SW1:Port1) <-> (PLC1:eth0)

(R1:LAN2) <-> (PC1)

Another thing to note is that both (SW1) and (R1) are capable of VLAN. (PC1) supports VLAN tagging and (PLC1) does not support VLAN.

I've played around with static routes between the networks to no avail.

1.) Is this even possible?

2.) Is this way outside the normal?

3.) If this is possible, how do I go about it?

If anyone has any information to point me in the right direction, please share.

Answer 1

Well, right off the bat, you can't normally route from one subnet (172.16.0.0/16) to the same subnet (172.16.0.0/16); this is a layer-2 (switch), not a layer-3 (router), thing. A router receiving a packet destined for the subnet on which the packet originated will just drop the packet.

Some Cisco routers can do IRB, but I don't know about the RV130, and this would put them on the same layer-2 domain, not a layer-3 tunnel between them. Also, I have seen proxy ARP do strange things where printers assigned IP addresses on the wrong subnet can be reached by both the correct and other subnets, and, again, this, also, would not be conducive to a layer-3 tunnel.

To create a PPTP VPN, I think you are going to need different subnets for the devices. If one of the devices can do VLANs, you could try assigning a trunk to it with both its 172.16.0.0/16 address and a different subnet on another VLAN.

What you want to do with what you have is just not how networks work.