Re: Windows 2000 server as Network Router

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This is a common question and I would add this to Phillip's expanation.
It really just says the same things in a different way.

When you enable IP routing it will forward traffic between the
interfaces. But it can only forward traffic which actually gets to the
router! Making changes at the router itself cannot fix this. You need to
make changes elsewhere in the network to get the traffic to the router.

In the simplest case of one router, it works fine. One each client you
set the default gateway to be the local router NIC. Traffic in the local
subnet is delivered directly (ie "on the wire" using hardware addressing).
Traffic for the "other" subnet is sent to the router. It can deliver the
traffic directly because it has an interface in the other subnet. The setup
for this is simple.

clients
192.168.11.x dg 192.168.11.1
|
192.168.11.1 dg blank
router
192.168.21.1 dg blank
|
192.168.21.x dg 192.168.21.1

If one of these subnets has another router, this usually fails. It fails
because the clients are set to use the "other" router as their default
gateway (to contact another site or the Internet). Traffic for the second
local subnet now goes to the external router and is lost. To solve the
problem you need extra routing to get the local traffic to the internal
router.

You can do this by adding a static route to every client to send traffic
for the other local subnet to the internal router. This will override the
default route, and get the local routing working. A simpler approach is to
add the extra route to the external router. The traffic for the local subnet
will then be redirected (or "bounced") to the internal router. A typical
setup for this would look like

External network
|
external router
192.168.11.254
|
clients
192.168.11.x dg 192.168.11.254
|
192.168.11.1 dg 192.168.11.254
internal router
192.168.21.1 dg blank
|
clients
192.168.21.x dg 192.168.21.1

If you add the extra routing to the external router eg

192.168.21.0 255.255.255.0 192.168.11.1

the local subnets will be able to route correctly. In addition, the
clients on the internal subnet (192.168.21.0) will also be able to see the
external network. Traffic will go out by default routing and get back
because of the route you added to the external router (to forward traffic
for 192.168.21.0 to the internal router).

xisnet wrote:
> Hi All,
>
> I have a server with 2 NICs, I already configured RRAS to make my
> server as network router. Below the configuration has been done.
>
> Ethernet 1 (connect to Subnet A)
> IP Address : 192.168.128.3
> Subnet Mask : 255.255.255.0
> Gateway : 192.168.128.254
>
> Ethernet 2 (connect to Subnet B)
> IP Address : 192.168.8.2
> Subnet Mask : 255.255.255.0
>
> Now from subnet A I can ping the computer at Subnet B. But I can't
> ping the computer in Subnet A from Subnet B. The following my Static
> IP Route Table:
>
> Interface List
> 0x1 ........................... MS TCP Loopback interface
> 0x1000003 ...00 00 4c 9f 03 3c ...... Intel(R) PRO/1000 Adapter
> 0x1000004 ...00 00 4c 9f 03 3b ...... Intel 8255x-based Integrated
> Fast Ether
>
> =====================================================
> Active Routes:
> Network Destination Netmask Gateway Interface
> Metric
> 0.0.0.0 0.0.0.0 192.168.128.254 192.168.128.3
> 1 127.0.0.0 255.0.0.0 127.0.0.1 127.0.0.1
> 1 192.168.8.0 255.255.255.0 192.168.8.2 192.168.8.2
> 1 192.168.8.2 255.255.255.255 127.0.0.1 127.0.0.1
> 1 192.168.8.255 255.255.255.255 192.168.8.2 192.168.8.2
> 1 192.168.128.0 255.255.255.0 192.168.128.3 192.168.128.3
> 1 192.168.128.3 255.255.255.255 127.0.0.1 127.0.0.1
> 1 192.168.128.255 255.255.255.255 192.168.128.3 192.168.128.3
> 1 224.0.0.0 224.0.0.0 192.168.8.2 192.168.8.2
> 1 224.0.0.0 224.0.0.0 192.168.128.3 192.168.128.3
> 1 255.255.255.255 255.255.255.255 192.168.128.3 192.168.128.3
> 1 Default Gateway: 192.168.128.254
> =====================================================
> Persistent Routes:
> None
>
> Thanks,
> Jai


.

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