Two routers on one modem

[thenetworker]

Hello!
I am planing to connect two wireless routers to one modem. The modem handles the conversion from the optical fiber to normal ethernet connection.
In order to make the internet work on one router I must connect the router to the modem and then change the router's settings (Static IP), which means that I must tell the router the following connection parameters : IP, Gateway and DNS.
Is it possible to connect two routers on the same modem, because I suppose that I can't use the same connection settings for both routers. If I keep the gateway and change the IP will the connection be successful?
Thank you in advance!

 

[kanewolf]

Only if you buy two connections from your ISP. Generally a modem only provides one external IP address.

 

[finitekosmos]

You absolutely can, but a lot depends on how you have your network configured, and the reasoning for doing what you are doing. I'll outline two common scenarios for a dual router configuration.

1. An Internet Facing Router and an Internal network facing router.

This is where you have the WAN port of the first router connected to your Modem, you can then connect the WAN port of the second Router to a LAN port on the first router. Router 1 acquires its configuration from the modem, and Router 2 acquires its configuration from Router 1.

If both routers have firewalls, this type on config can be used to create a cheap version of a network DMZ. You could then independently configure each firewall to improve security with computing devices connected to the first modem receiving the benefit of the firewall available on it, and computing devices connected to router 2 benefiting from heightened security by being behind both router 1 and router 2's firewalls.

2. An Internet facing Router with the second router acting as a repeater or wi-fi extender.

I have two routers that are the same brand but are different models. In my home configuration My Fiber router is too far away to service my home completely and so I needed a second device to act as a WI-Fi repeater (I could use a Wi-Fi extender/booster but I had a spare router so I used what was handy). In my configuration the secondary router has had its WAN function disabled and it acts simply as a WiFi extender for my wi-fi devices. My Internet facing router has been configured to identify the second router and configure it to act essentially as a WiFi mesh device.

However your usage case may differ and you haven't really talked about what it is exactly you want to do. Using two routers can open up some interesting new configurations but its best to know what it is you want to do first then you can configure them to suit the task. Your question sounds more like you have some extra/spare hardware and are wondering what you can do with it.

 

[jsmithepa]

U would get a more direct answer if u disclose the reason behind this want.

 

[michael.stringer.2.0]

So, generally yes. Almost all modern modems are wired/wireless routers themselves. The convert your internet IP into a "internal" ip - 192.168.x.x or 10.x.x.x. Your wireless routers will do the same thing. The ONLY requirement is that the wireless addresses moust be different than your modem's internal IP.

So, if your modem is 192.168.0.1, you will need EACH wireless router to have internal IPs different - 192.168.1.x, 192.168.2.x, etc.

Here's the wiring hookup:

Wireless router │
├ Modem
Wireless router │

You'll be in a "double NAT" setup - these setups sometimes have issues with some gaming services, or other streaming services. If you connection to PSNetwork or XBox Live - look for their recommendations for double NAT configurations.

What is NAT? Network address translation - it converts one network address to another. In case of your modem, it takes your internal IPs and translates them to your Internet IP so you can browse the internet. Your wireless routers will do the same thing.

Your OTHER option is to disable all DHCP on your wireless routers and hook up a regular port to the internet modem - this removes the "router" portion of your wireless router and turns them into access points. All the addressing and NAT will go to the modem. All your wireless will have the same addressing and go out directly through the modem.

 

[thenetworker]

U would get a more direct answer if u disclose the reason behind this want.

I want to connect two routers on one modem to split the network load.I am trying to create two separate networks. I could connect one router to the modem and then connect the second router to the first router, but on a large network (300+ devices) the first router will be full of network traffic.
So, I would like to let the modem (with no router capabilities) deal with this instead of putting a lot of load onto a single router.

 

[thenetworker]

So, generally yes. Almost all modern modems are wired/wireless routers themselves. The convert your internet IP into a "internal" ip - 192.168.x.x or 10.x.x.x. Your wireless routers will do the same thing. The ONLY requirement is that the wireless addresses moust be different than your modem's internal IP.

So, if your modem is 192.168.0.1, you will need EACH wireless router to have internal IPs different - 192.168.1.x, 192.168.2.x, etc.

Here's the wiring hookup:

Wireless router │
├ Modem
Wireless router │

You'll be in a "double NAT" setup - these setups sometimes have issues with some gaming services, or other streaming services. If you connection to PSNetwork or XBox Live - look for their recommendations for double NAT configurations.

What is NAT? Network address translation - it converts one network address to another. In case of your modem, it takes your internal IPs and translates them to your Internet IP so you can browse the internet. Your wireless routers will do the same thing.

Your OTHER option is to disable all DHCP on your wireless routers and hook up a regular port to the internet modem - this removes the "router" portion of your wireless router and turns them into access points. All the addressing and NAT will go to the modem. All your wireless will have the same addressing and go out directly through the modem.

Thank you for the reply! Unfortunately, my modem (pretty old) does not act as a router itself. I must configure the devices that I connect to it with the given settings for the static IP.

 

[jsmithepa]

split the network

Perfect.

1. Can only tie more than one WIFI router to the modem if said modem is also the NAT device. U know modem does NAT if it has more than 1 LAN ports on its back. If modem is not doing NAT then your first WIFI router is doing it, and there can be only 1 NAT device (well u can have more than 1 NAT but it creates more problems).

2. 300 potential users you should really be using business-class WIFI routers. Two separate WIFI routers physically mounted at a distance does widen your WIFI coverage though.

 

[failboat]

300 devices is this for a business?

You can segment out each group and vlan them. Then apply limiters at the router for WAN traffic.
Pfsense has very good limiter config. x86 can handle very heavy loads. You can build it out on Xeon with ECC ram.

 

[USAFRet]

a large network (300+ devices)

You need to be looking at commercial level devices.
Not trying to hack together some "network" with cheap equipment.

And a LOT of other factors come into play.
Distance, building construction, what type of data is this, etc, etc, etc.

 

[kanewolf]

U would get a more direct answer if u disclose the reason behind this want.

I want to connect two routers on one modem to split the network load.I am trying to create two separate networks. I could connect one router to the modem and then connect the second router to the first router, but on a large network (300+ devices) the first router will be full of network traffic.
So, I would like to let the modem (with no router capabilities) deal with this instead of putting a lot of load onto a single router.

For this many devices, this sounds like a commercial installation. You MAY have multiple public IP addresses with your ISP. But, I agree with @USAFRet, you need to look at business class hardware. A wired router, with multiple WIFI access points, tied to the router. This is not something that should be using home quality hardware.
A business class router like a Ubiquiti Edge Router can handle close to gigabit network at wire rates. I don't think you have to work about the router being overloaded.