Regestry edited but still no IPForwarding

Question

A simplified view of the current setup:

• Host A1: 192.168.1.2
• Host A2: 192.168.2.2
• Host B: 192.168.1.1, 192.168.2.1, 192.168.10.1
• Device C: 192.168.10.2

a bit more detailed:

• Host B, A1 and A2 have 3 NICs in summary (all configured for different IPAdresses)
• all IP-Adresses and masks are fixed (no DHCP)
• all hosts have Windows 7 Ultimate
• There are more devices in the x.x.10.0-network

What do I want?

Be able to ping from Host A1 to Device C; access Device C via http.

What have I done?

Host A1:

cmd -> route add 192.168.10.0 mask 255.255.255.0 192.168.1.1

Host B:

• HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\ Services\Tcpip\Parameters\IPEnableRouter -> 1
• Service "Routing and Remote Access" started
• Firewall is off
• rebootet several times (its windows .. just to be sure :P )

The result: I can ping from HostA to HostB (192.168.10.1) but not Device C. From all I've found in the internet and all I know about networking, nothing more need to be done. But I'm coming from the linux-world and had been proved wrong multiple times about such assumptions before. Any advices what needs to be checked/ done?

Answer 1

HostC needs a route to HostA through HostB.

Now you may be thinking But HostC sees the source MAC address of the packet from HostA as coming from the MAC address of HostB, so why doesn't HostC send data back to that MAC address of HostB?

The answer is because routing occurs at layer 3, not layer 2.