[FAQ] Using two routers together/ Extending Wi-Fi

mickevh

Distinguished Member
A question often posted in this forum concerns how to go about "using to routers together" or "extending wifi" using extra routers. Following is a...

A) Short Version
B) Long version
C) Backgound Information

Special and or customised firmware for routers should not be necessary.

EDIT 2014: - I've attached a "block diagram" to this post which in conceptual terms illustrates how a typical SOHO router functions. Actual implementation will of course vary, (for example, the NAT/Firewall could be argued to be part of the same "thing," the DHCP could be bound to the switch,) and some have additional features, but the basic conceptual functionality seems to hold for most SOHO routers. For routers with built in modems, the modem effectively sits between the "WAN" and "NAT" as I've drawn it. A.B.C.D and W.X.Y.Z show (respectively) where "WAN" and "LAN" IP addresses are bound logically as I've drawn it.

Short Version

1. Change the IP address of all secondary (non-ISP connected) routers so that they are unique within your LAN.
2. Disable the DHCP Server in all secondary routers.
3. Connect secondary routers to primary (ISP connected) router using their "LAN" not their "WAN/Internet" ports.

Long Version

1. Decide which is to be your "primary" (ISP connected) router. All other routers are "secondary" for the purposes of this discussion.

2. Surf to the admin screen of your primary router and make a note of it's "LAN" IP address and the range of IP addresses it's DHCP Server provides.

In SOHO kit, these will very probably be a variant of 192.168.x.y. Ensure you have a "spare" IP addresses available for each secondary router. Note that these need to be outside the range provided by the primary routers DHCP Server and not in use by anything else. See end of this post for further information on IP addressing.

3. Disconnect a "configuration computer" that you will use to set this regime up from everything and turn off it's Wi-Fi if it has it.

For each secondary router:

4. Physically disconnect it from everything then connect the configuration computer to the secondary router (LAN port) and allow the PC to acquire an IP address from the secondary router.

5. Surf to the secondary router's admin screen.

6. Set the router's LAN address to one of the "spare" addresses determined previously. Some routers may drop your connection at this point and/or require a reboot. If necessary, do so. The router may also have changed the DHCP range it serves out (leaving your configuration computer with a "wrong" IP address,) so a reboot of the confguration computer to cause it to acquire a new IP address might be necessary. Thence surf back to the router's admin screen using the new IP address you just gave it.

7. Find the secondary router's DHCP Server settings (note "Server" not "Client") and turn the DHCP Server off. The only functioning DHCP Server in your network should be the one in your ISP connected "primary" router.

8. Repeat from step "4" for any additional secondary routers.

9. Connect your secondary routers to you primary router (or each other or anything else) using their "LAN" and not their "WAN" AKA "Internet" ports. The WAN/Internet ports on your secondary routers shall forever have nothing connected to them.

10. Reconnect the configuration computer as you would in normal use and enable it's Wi-Fi if you turned it off earlier. Again a reboot of the PC may be necessary to pick up an IP address issued by your primary router.

11. Set up Wi-fi on each router as desired.

12. You might also care label each router with it's IP address. It's surprising how quickly one forgets.

Backgound Information

The things that we all know as "routers" are rather badly named. They are multi-function devices containing (for example) a modem, ethernet switch, router, firewall, NAT translator, DHCP Server and Wi-Fi Access Point amongst others. Note that last item - Wi-Fi is availed by Access Points. An Access Point is built-in to that thing we have at home we call a "router." It is possible to build a perfectly good multi-cell Wi-Fi network using Access Points. "Routers" are not necessary to "do Wi-Fi."

It is not uncommon for people to believe that Wi-Fi is availed by "routers" but we now know this is not the case. When SOHO routers first entered the market place, they didn't contain Wi-Fi Access Points, but were otherwise identical to the "Wi-Fi Router" that we know today.

So why do people use routers as Wi-Fi Access Points? Sometimes it's because they have an old one lying around, or can buy them cheaper than a stand alone Access Point, most notably on the online auction sites. Sometimes it's because they also want a few extra ethernet ports as well as Wi-Fi and using a router is a convenient way to avail a little AP/switch combo box at low cost.

To use routers as an AP or AP/switch combo, we need to (ironically) not use it's routing, NAT, firewall and a few other functions. No problem so far, if we simply leave the WAN/Internet port disconnected and cable routers together using their LAN ports, we achieve this.

However, a further problem occurs with DHCP. Most SOHO routers have a DHCP Server built in to automatically provide IP addresses to any client devices connected to them. A router's DHCP Server is often pre-configured to distribute IP addressing information that designates itself as being the point of contact for the rest of the world. Essentially the IP addressing information they provide says "if you want to connect to something outside your local network (LAN,) talk to me and I'll forward the request on for you."

That's fine in a little SOHO LAN with only one router, but becomes problematic when we have multiple routers (with the secondaries having nothing connected to their WAN/Internet ports) as the secondary routers cannot handle the requests to connect to the outside world.

The easiest way to deal with this, is to ensure that all the IP addressing is handled by your primary, ISP connected router that does know how to talk to the world. The easiest way to achieve this, is to disable the DHCP Server on all the secondary routers so that only the primary router gives out IP addresses.

On an IP LAN, every device must have a unique IP address. Each router is one such device. Often they ship pre-configured to some common default IP address. 192.168.0.1 and 192.168.1.1 for example. If you connected two routers from the same manufacturer or of the same model together it's very like they will have the same IP address - the manufacturers generally don't randomise them - and duplicate IP addresses are a no-no.

Hence, we need to ensure that all our routers have a unique IP address. And if we ever want to access them in future, say to adjust their setting or update the firmware, that will be much easier to do if they are all in the same "subnet" range as it's known. Without getting terribly boring about how IP addressing works, if you use subnet mask 255.255.255.0 on your LAN, (most SOHO kit seems to by default,) and IP addresses of the format 192.168.X.Y; keep "192.168.X" the same on everything and make sure "Y" is unique, outside your primary routers DHCP range, not "0" or "255" and between 1 & 254.

EDIT 2017: Don't worry if secondary routers "complain" that the "Internet isn't there." E.G. Some BT HomeHubs flash their blue "broadband" lights constantly, other routers show error messages in the admin screens. This is expected.

Most SOHO routers "expect" to find the Internet through their WAN/Internet ports and aren't designed to "look" for it anywhere else. Using the regime described in this FAQ, by definition, all "secondary" routers have no connection to their WAN/Internet ports and thus cannot find the Internet through them and are not designed to seek the Internet anywhere else. So they may generate error states.

But that's OK, if you've configured things as described in this FAQ, the client devices will be finding their way the the Internet through your ISP connected "primary" router and we can ignore any error messages on the secondary routers about Internet not being available. Indeed, if the "light" gets irritating, some routers may let you "disable" the Internet in their UI (though many don't.)

I think that's everything. If anyone one finds any errata, or one of my frequent spolling or granma erros, PM me.
 

Attachments

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Chris Muriel

Distinguished Member
I'm giving this a bump so it (temporarily) appears near the top.

It reallly needs a mod to make it into a sticky.
 

maxwell

Distinguished Member
Nice explanation and +1 to make it a sticky
 

leecavturbo

Active Member
any good / correct? will be edited where needed
the options are router 3 connected to 2 or 1 but not both

i.e
router 1 ip = 192.168.0.1 (typically the default for routers) but should be set by you "manually set" dhcp on
router 2 ip = 192.168.0.2 manually set by you, dhcp off
router 3 ip = 192.168.0.3 manually set by you, dhcp off
so the starting dhcp address for router 1 to give out ip's must be from 192.168.0.4 or higher.
if not and router 2 is off and you connect a device to router 1 it would give out 192.168.0.2 to that device but as soon as router 2 is powered you would have a ip conflict. i.e 2 x 192.168.0.2
the subnet can be vastly different (subnet=192.168.0) but must be the same throughout for the same network i.e 192.168.2.1 or 10.0.0.1 however subnet changes can and will adjust how many ip addresses and/or the range you can have. there are online calculators that will show you the available addresses/ranges for any given subnet.
don't let the above be daunting. stick to something like 192.168.1-10.1 and you'll be good.
 
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mickevh

Distinguished Member
Spot on. Though very much emphasise that "option 1" and "option 2" are mutually exclusive alternatives. If you hooked up both, you'd have a "loop" in the ethernet topology and they are very bad things. If you loop ethernet, your LAN would tank very quickly.
 
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kevismit

Standard Member
Hi, i think you should maybe add the following info to your excellent post.
On both primary and secondary devices the SSID, Network and Security should be set identically. Don't forget to add a web password to both devices to keep out intruders. As I found out, the wireless channels must be different on each device. You should now be able to seamlessly roam throughout the area. My iPhone works a treat, however i still have problems with my Netbook (Win 7). I am wondering if my Video Sender is the culprit and need to further investigate.
Hope this helps.
Any comments please reply. KSS:facepalm:
 

Courtjezter

Distinguished Member
Right,

So i have a router in my front room, which is the opposite side to the av equipment i have. I have one 10m ethernet cable, but 4 pieces of equipment that could use it. Would i have to use the above method to split that one ethernet into four. Or is their another way i can do this? (apart from moving the router closer to the equipment.)
 

leecavturbo

Active Member
a normal or "pc" correct way is to use a switch/hub. however many ppl have spare routers or they are cheap to buy and will act as a switch to give more ports
 

mickevh

Distinguished Member
Don't forget that you'll need a 5 port switch for such a configuration: 1 port for each piece of equipment (4) plus one for the uplink to the router.

We've seen 5 port switches available in the SOHO market for less than a tenner.

If you do have a spare router with enough ports, regard the "LAN" ports in your router as a "switch." 5 (LAN) port routers are rare (I've never heard of one, but that doesn't mean they don't exist.) Switches don't need IP addresses to "work", but you'll have to disable the DHCP Server in a "router-used-as-a-switch" to avoid the IP addressing issues as discussed above.

However, for the sake of a tenner, I'd buy a little switch. Nothing to configure, power it up, plug in, job done.
 
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Muzic man

Novice Member
Right,

So i have a router in my front room, which is the opposite side to the av equipment i have. I have one 10m ethernet cable, but 4 pieces of equipment that could use it. Would i have to use the above method to split that one ethernet into four. Or is their another way i can do this? (apart from moving the router closer to the equipment.)
Can someone tell me is a Netgear N150, a hub then ? My router went down over christmas so i went to Argos and bought one of these thinking it would work the same, only to find there's no phone connector on it. Someone lent me a replacement sky router whilst i got a replacement one from e-bay. I took this back to Argos who informed me they dont do refunds on this item, so i'm stuck with it. But if this can be connected to the other router as a hub it could be just what i need.
 

leecavturbo

Active Member
It can be used as a hub (switch) but you will only have 3 Ports left as you need 1 for the incoming cable. You can't connect it to the wan port (first or fifth port depending on how you look at it)
 

mickevh

Distinguished Member
Yes - at the very least you'll have to turn off it's DHCP server.

And if you're going to that trouble, you may as well do the rest and benefit from additional wi-fi AP in your infrastructure (or turn the wi-fi off if you don't want it) and ensure you have no IP address conflicts.

Just follow the instructions above.
 

Muzic man

Novice Member
Yes - at the very least you'll have to turn off it's DHCP server.

And if you're going to that trouble, you may as well do the rest and benefit from additional wi-fi AP in your infrastructure (or turn the wi-fi off if you don't want it) and ensure you have no IP address conflicts.

Just follow the instructions above.
Thanks very much for your help. :thumbsup:
 

franko3

Active Member
Hope someone can help please, just changed my dir-615 with ddwrt for a stock dir-655 and wanted to use the 615 to extend my wifi coverage.
I changed all the settings that i thought I needed (I read that i should turn off security on 2nd router) and assumed the primary router would take care of security.
I can now connect wirelessly across the house - the thing is that the extended wifi is open & doesn't ask for a key. Should I enable wpa2 on both routers?
Many thanks for any advice.
 

leecavturbo

Active Member
No mate you need security on both routers. The only thing you turn off is dhcp on the secondary router and any others you might add to your network
 

franko3

Active Member
Thanks for that, have enabled it now with same wifi password as other router and all working ok.
Got a bit confused with the setup as I flashed it with ddwrt & there seems to be a few more variable settings than with the stock firmware.
Many thanks for the prompt reply.
 

NobleBenj

Novice Member
Just about to create a thread when when I stumbled on this thread:

"Two buildings 30M apart, one with broadband and the other without.

As I do not wish to add a second telephone line to my property, how can I get wi-fi in the second building using the existing broadband service?"

Is this the solution above? i.e Running a 30M cat6 cable out of the existing lan port of the wireless router to another (old) wireless router in the second building. Thus giving me two wireless zones on the same network?

Thanks in advance.

Edit: have'nt been here in a while but I think Mr AVF just added links hmmm?
 

NobleBenj

Novice Member
Just about to create a thread when when I stumbled on this thread:

"Two buildings 30M apart, one with broadband and the other without.

As I do not wish to add a second telephone line to my property, how can I get wi-fi in the second building using the existing broadband service?"

Is this the solution above? i.e Running a 30M cat6 cable out of the existing lan port of the wireless router to another (old) wireless router in the second building. Thus giving me two wireless zones on the same network?

Thanks in advance.


Edit: have'nt been here in a while but I think Mr AVF just added links hmmm?
bump
 

Iccz

Distinguished Member
Is this the solution above? i.e Running a 30M cat6 cable out of the existing lan port of the wireless router to another (old) wireless router in the second building. Thus giving me two wireless zones on the same network?
Bang on mate :)

Depending on where you're running the cables you might need to make sure you get cable suitible for outdoor use, but the above will work :thumbsup:
 

playsah

Standard Member
Hello
I need big help. I'm new here & at the risk of sounding stupid really need help with this topic. I started to attempt this, this morning to extend the wireless within the home from my new Virgin Media Modem/Router as it's not the best at wireless transmitting.
So trying to follow instructions from a magazine started on the settings changes within old (2nd) router to match router 1 and along the way it must have needed a restart or something & I remember a msg from my US Robotics USR5461 as it was rooting telling me to log into it's settings in future I'd need to use the i.p. address I'd assigned to it within the changes to match the 1st router but I don't remember getting to that stage and now I can't access it's settings to carry on or do anything at all. Oh also the reset button on the back of the (2nd) US Robotics router doesn't reset and allow me to log into it's settings via 192.168.2.1 :(
I know I rushed it and I should have took more time & care.
Any help would be hugely grateful!
Thank you.
 

mickevh

Distinguished Member
I'd suggest you reset USR to factory default and start again using the instructions above. I would probably be a good idea to read through the instructions first so you're clear what you're going to be doing before you start.

To reset, many SOHO routers have some form of "reset" hole round the back which you poke a straightened paper clip into for a few seconds. Doubtless the manual will tell you and also what the default IP address and loginid/password are.
 
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Chubster

Novice Member
I intend to use my spare router as an extra switch but I do not need its wireless capabilities, its in the same room as my main wireless router.

Can I turn this off and if not is there any harm in leaving it on. Will it cause interference ?
 

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