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Flagbridge-NW
Flagbridge-NW, Consultant
Category: Networking
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Experience:  Paid for university with 10+ years as a Network Engineer.
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How do I connect 2 LANs together to form a WAN

Resolved Question:

How do I connect 2 LANs together to form a WAN? Do I use a router or a switch to connect 2 routers/networks together?
Submitted: 6 years ago.
Category: Networking
Expert:  Flagbridge-NW replied 6 years ago.
To connect two LAN's together you need to use a device that is capable of Layer 3 communication.

Most often this is a router, however there are many Layer 3 switches available that can do the same task.

If you give me more information about your actual individual needs i can expand my answer if required.

Regards
Customer: replied 6 years ago.
I have networks, each with its own NAT router. I also have a layer 3/smart switch. Do I just connect the 2 routers to the layer 3 switch so hosts on both networks can communicate with each other?
Expert:  Flagbridge-NW replied 6 years ago.
Do you want both talking to the internet as well?
Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post: I have a proxy server/ISA server 2004. I want both to get to the Internet through that proxy server.
Expert:  Flagbridge-NW replied 6 years ago.
Ok so here is what you can do (I dont have your network diagram so please bare with me).


Network 1 (N1). We will say is network 10.0.0.0 255.255.255.0

Network 2 (N2). We will say is network 192.168.0.0 255.255.255.0

ISA Machine. (ISA). We will say it is on its own network of 172.16.0.0 255.255.255.0


Take your lawyer 3 switch.

On interface 1, give it the ip address 10.0.0.254 (your gateway address or default route address for that subnet). Plug N1 into Interface 1.

On interface 2, give it the ip address 192.168.0.254 (your gateway address or default router address for that subnet). Plug N2 into Interface 2.

On the last interface on the switch give it an IP address 172.16.0.254 (your gateway address or default router address for that subnet) Plug ISA into that interface. IP the server is 172.16.0.1

------------

Routes,

N1 all machines on N1 have a default route of 10.0.0.254

N2 all machines on N2 have a default route of 192.168.0.254

ISA, Now we need to add a couple of routes to this machine. You need to add

10.0.0.0
192.168.0.0
172.16.0.0

All to point to 172.16.0.254.

You will also need a default route pointing to the external interface (if directly connected to the net or to a router).

The ISA machine can nat for all the 10, and 192.168 address if you want. OR you can put routes on the router so you are only NATing once.

==============


The switch will need a default route pointing to the ISA IP (172.16.0.1)


Flagbridge-NW, Consultant
Category: Networking
Satisfied Customers: 4618
Experience: Paid for university with 10+ years as a Network Engineer.
Flagbridge-NW and 4 other Networking Specialists are ready to help you
Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post: A clarification is needed. When you say, "On interface 1, give it the ip address 10.0.0.254...", do you mean assign the ip address 10.0.0.254 to router 1? Or do you mean assign that IP address to the port of the switch? If you mean assign it to the port of the switch, I'm not sure if that could be done. My layer 3 switch is a netgear switch and I haven't seen a feature in the switch setup pages that will allow me to assign an IP address to a port.
Expert:  Flagbridge-NW replied 6 years ago.
Port 1 of your layer 3 switch.

You said you had a layer 3 switch, so we are using the switch as the internal routing device.

You may be able to add subnets to the switch, or routes to the switch.

regardless, if it will act as a layer 3 device, it needs to obtain an IP address on each network it will be routing.

Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post: I"m not sure how that can be done on the switch. What about replacing the switch with a router. Can I used any router to connect the 2 routers/networks together? Or does it has to be a special type of router? And how do I connect the 2 routers/networks to the main router? Do I need to setup any routes/configurations?
Expert:  Flagbridge-NW replied 6 years ago.
Yes you need to do some significant configuration,

In addition you need a router with three PROGRAMABLE ethernet interfaces
Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post: Another Expert told me that I could use any router, but he hasn't gotten back to me on how exactly to connect the 2 networks to the primary router and its configurations. Please explain "significant configuration". Thanks.
Expert:  Flagbridge-NW replied 6 years ago.
You can not use any router, as then you have no interface to get to the internet.

Youa re trying to get three networks connected together.


You need to configure the router to tell it what networks are on what sides of the interfeace and how to allow certain traffic to go between.

Anyone who says you can use any router is incorrect.

Expert:  Flagbridge-NW replied 6 years ago.
I see that you have now included information in your second question not in your question here.

Would you prefer I opt out?
Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post: Here is what I got from another Expert and a lot of the researches that I have done were saying that any router could be used to connect 2 or more networks together.

From Expert: "Hello. Yes, you can use any router to accomplish this - that is what a router is for; to connect two networks. You will just need to provide the "WAN" side of the router with an IP address on one network and have all nodes of the second network come into the router.

If the two networks are in the same location, you might consider simply modifying the subnet instead - for example, use 192.168.1.x for one network and 192.168.2.x for the other. Then you wouldn't necessarily need a router at all."


My Reply: "Ok, here is my situation. I have 2 subnets/networks, 192.168.100.1 and 192.168.200.1. Each network has its own router. So let's called the router with IP address of 192.168.100.1 R1 and 192.168.200.1 R2. What I did previously was I connected the WAN port of R2 to one of the switch ports of R1. Hosts from R2 were able to ping R1 but not hosts on R1. Also, hosts from R1 cannot ping R2 or hosts on R2. So I was thinking that it might need a third router to connect those 2 routers/networks together so that hosts on R1 can communicate with hosts on R2 and vice versa.

Let's called the third router, the primary router that will connect R1 and R2 together, as R3. What I did was I connected the WAN port of R1 and R2 to the switch ports of R3. Hosts from both R1 and R2 were able to ping R3 but R1 still cannot communicate with R2 and vice versa. What am I missing?"

So I don't understand the fact that it can only be done using a router with three PROGRAMABLE ethernet interfaces. In fact, I searched online and found very few to almost no information about router with three programable ethernet interfaces. If 2 or more networks can be connected via any router, how and what kind of configurations needed to be done?
Expert:  Flagbridge-NW replied 6 years ago.
I first started out by saying "Ok so here is what you can do (I dont have your network diagram so please bare with me)."

You didnot explain any of your previous setup to me.

I see why things are not working, and certainly would not engineer it like that.

R1 has no idea how to get to R2 because no static routes exists for it telling it

What type of routers are these

Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post:

First of all, thanks for helping out. Please do not assume that I will not accept answer because I will accept answer(s) by the end of the day. I usually get all of my answers and then accept one or more once the problem is solved.

To your question, these are netgear routers with NAT. Let me know if you need any additional info. Thanks.

Expert:  Flagbridge-NW replied 6 years ago.
Do you have a network diagram?

Do you have the model number of the L3 switch and the netgrear routers?

Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post: My equipments are at home and I'm still at work. This is my senior project for my BS in IT. As of right now, I have 3 netgear routers with NAT and a layer 3 netgear switch. I want to simulate 2 networks connecting together to form a WAN and both networks are able to communicate with each other using the equipments I have. Let me know if you know of any better way doing it (as long as there are 2 networks of different subnet connected together and can communicate with each other).
Expert:  Flagbridge-NW replied 6 years ago.
Ok there are a few things you could do PROVIDED that the routers can support it.

In your first scenario you have two issues.

1. If you are natting and the nats are not static, then traffic can only originate from INSDE.

2. If you are sending traffic out an interface you need to know how it will get back. if your router does not know where to send the traffic then it will drop it.

This is why you need static routes, which I explained in detail above.

3. Based on what you have described (sending all traffic through your ISA Proxy, well that is acting as a firewall so BOTH networks need to be on the INSIDE of it.

4. You want to avoid NAT where possible. Use it only when necessary and when you know why you need it.

The feature description on your netgear router may be TADITIONAL ROUTING, which will disable NAT, but force you to enter your static routers, networks etc.

For example you could create a different VLAN for each subnet, and then create a VLAN trunk to your router, which would then route the traffic back and fourth.
Customer: replied 6 years ago.
Reply to Flagbridge-NW's Post:

How do I disable NAT on a router? When I look through the netgear router's setup page, there are two router functions, "Run router as gateway" and "Run router as router". What is the difference between the two? And by choosing "Run router as router", will that disable NAT?

Will it work if I:
1) disable NAT on all three routers, R1, R2, and R3
2 connect WAN port of R1 to R3 switch port
3) connect WAN port of R2 to R3 switch port
4) connect ISA server to R3 switch port

I will have all of the external traffic to the Internet route to the proxy server. Will the proxy server do NAT on incoming traffic? Will this work?

Expert:  Flagbridge-NW replied 6 years ago.
Yes Router as a Router should disable the NAT.

Routes will not know what to do unless you program and tell it. If you disable NAT you need to set up routes.


You are using equipment that is not designed for this type of configuration. You really shouldbe using an 800 series Cisco router for this.

You always start something like this with a diagram.

So before we continue, as I have spent nearly 45 minutes on your problem today, we need to standardise the approach.

Draw a diagram, including

ALL devices and model
ALL interfaces
ALL IP Address and Subnet masks
ALL Machines, and their features as required
ALL traffic lines, and traffic paths.
CLOUDs for the various networks.

When you have that done, I can review it for you.

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