Basic Local LAN to LAN routing


N

NewarkGoss

I have two LANs in the same building I whish to interconnect. Each
needs a DHCP server. One has a gateway to the Internet and the other
does not.

LAN A: 192.168.1.0/24 gateway 192.168.1.20

LAN B: 192.168.11.0/24 no gateway

I have a WS2K3 R2 machine with two NICs. On the 192.168.1.0 LAN, it
has a fixed IP of 192.168.1.99. On the 192.168.11.0 LAN, it has a
fixed IP of 192.168.11.1.

I installed RRAS - custom - LAN routing. The DHCP gives the IP
address of the NIC on the server as the gateway for each respective
side.

From a machine on the 192.168.1.0 side, I can ping the 192.168.11.0
side. Because the gateway is in the configuration of the NIC on the
server, I can access the Internet. Also, RDC to a machine on the
192.168.11.0 side from the 192.168.1.0 side is possible.

The 192.168.11.0 side cannot get to anthing beyond the 192.168.1.0/24
subnet.

According to all the things I can find on using RRAS in this way, it
should be working both ways, but is not.

Any ideas?
 
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K

Kurt

NewarkGoss said:
I have two LANs in the same building I whish to interconnect. Each
needs a DHCP server. One has a gateway to the Internet and the other
does not.

LAN A: 192.168.1.0/24 gateway 192.168.1.20

LAN B: 192.168.11.0/24 no gateway

I have a WS2K3 R2 machine with two NICs. On the 192.168.1.0 LAN, it
has a fixed IP of 192.168.1.99. On the 192.168.11.0 LAN, it has a
fixed IP of 192.168.11.1.

I installed RRAS - custom - LAN routing. The DHCP gives the IP
address of the NIC on the server as the gateway for each respective
side.

From a machine on the 192.168.1.0 side, I can ping the 192.168.11.0
side. Because the gateway is in the configuration of the NIC on the
server, I can access the Internet. Also, RDC to a machine on the
192.168.11.0 side from the 192.168.1.0 side is possible.

The 192.168.11.0 side cannot get to anthing beyond the 192.168.1.0/24
subnet.

According to all the things I can find on using RRAS in this way, it
should be working both ways, but is not.

Any ideas?

You'll need a couple more things which you may or may not be able to do
depending on your hardware and software. Let's start by reviewing what
works and doesn't work now.

1) You can ping from 192.168.1.0 (the ".1" subnet) to the ".11" subnet.
2) You can ping from .11 to .1.
3) .1 hosts can access the Internet
4) .11 hosts cannot access the Internet

The most likely problem is that your Internet Router can only perform
NAT for 1 subnet. If by some odd chance it's capable of multiple
subnets, it will need to be configured to perform NAT for the .11 subnet
and will need a static route back to the .11 subnet via the NIC on the
server.

If you can't do that (which is probably the case), since you already
have inter-subnet routing working using the NICs on the server, here's
what I'd do:

Go out and buy an inexpensive NAT ("SOHO", "Broadband", etc.) router
with two Ethernet ports. Configure the LAN side with an IP address on
the .11 subnet and the WAN side for the .1 subnet, and make the new
router's default gateway 192.168.1.20.

Then add a static route on the computers on the .11 subnet:
route add 192.168.1.0 mask 255.255.255.0 192.168.11.xx
(where 192.168.11.xx is the Server NIC)

If you are running an Active Directory you can do this with a startup
script from group policy. If not, you'll need to add it as a startup
script on each workstation, or put it in the "all users" "Startup"
folder - Users will need permissions to change TCP/IP settings if you
use the startup folder method. Then set your DHCP server to hand out the
new router as the default gateway for .11 clients. That way, any traffic
headed for the .1 network will go to the server, and any traffic bound
for the Internet will go to the new router, which will NAT it to it's .1
IP address and send it on the to 192.168.1.20 (gateway) router. The
gateway router will now be happy because it sees an IP address on it's
own subnet instead of an unknown subnet.

Kurt
 

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