Author Topic: 2 computers, 1 router  (Read 7678 times)

Julian

  • samoture
2 computers, 1 router
« on: 13 April, 2011, 10:18:09 pm »
We can't get 2 computers online.  Charlotte's computer works fine.  Mine can connect to our wireless network but won't then connect to the internet.  We've just tested it and if she connects through her phone, she can't through her computer - so it's only letting one device on at a time - and for some reason even with Charlotte disconnected, it still doesn't like my computer.  This is a brand new computer and my old one had the same issue.

Charlotte thinks this might be because we only have one IP address.

I have no idea because all of this is totally beyond me and I don't understand what most of the words even mean when I do an internet search.

Anybody got any good ideas (and solutions) that can be explained to a non-networker in easy terms?

andygates

  • Peroxide Viking
Re: 2 computers, 1 router
« Reply #1 on: 13 April, 2011, 10:21:23 pm »
Usually the IP address belongs to the router.  Inside your home network, you have a bunch of junk addresses that are given out by the router's DHCP, and it manages passing the connection off to the relevant PCs. 

If Charlotte's PC has an internet-real IP address, either you asked for that, or something weird is going on.

Open a DOS box (start > run > cmd) and do IPCONFIG, see what it says.  If it's 192.168.anything, that's sensible junk. 
It takes blood and guts to be this cool but I'm still just a cliché.
OpenStreetMap UK & IRL Streetmap & Topo: ravenfamily.org/andyg/maps updates weekly.

border-rider

Re: 2 computers, 1 router
« Reply #2 on: 13 April, 2011, 10:23:19 pm »
What sort of router is it ?

What routers do is allow multiple devices onto a network, give them their own IP addresses and share your internet connection (and the single IP address your ISP gives you) between them.  If it's not doing this, it's not doing its job.

One option is a factory-reset.  

Re: 2 computers, 1 router
« Reply #3 on: 13 April, 2011, 10:23:56 pm »
I can't help but, while we are here and as it sounds similarish#, our router which is a BT home hub will on occasion not accept a new computer access if one or more of the others are using it. In this circumstance re-booting the router then lets all the on line computers join.


#if it is nothing like at all, apologies for the thread hijack
[Quote/]Adrian, you're living proof that bandwidth is far too cheap.[/Quote]

Re: 2 computers, 1 router
« Reply #4 on: 13 April, 2011, 10:28:05 pm »
You should find the IP address of the router - probably 192.168.1.1 or 192.168.0.1
It will be the 'default route' of the PC which you do have connected to the Internet.

Use a we bb rowser to look at that IP Address.
Try to find the paeg which lists the currently connected devices, and let us know what that list is.

andygates

  • Peroxide Viking
Re: 2 computers, 1 router
« Reply #5 on: 13 April, 2011, 10:34:26 pm »
A bit of route diagnostics is also informative:

tracert Google

...will list each of the hops between you and the Elder Hive. 
It takes blood and guts to be this cool but I'm still just a cliché.
OpenStreetMap UK & IRL Streetmap & Topo: ravenfamily.org/andyg/maps updates weekly.

Julian

  • samoture
Re: 2 computers, 1 router
« Reply #6 on: 13 April, 2011, 10:38:51 pm »
[charlotte]
The internet facing router (provided by AAISP) is 192.168.1.1 and so is the Linksys router.  I've tried forcing the Linksys to be 192.186.2.1 and that worked, too.  But then we still had the problem of two laptops not being able to share the wireless.

DCHP is enabled on the Linksys (which I've told that it's no longer in Gateway mode, so it knows just to act as a wireless box for the line in from the AAISP router) and I genuinely can't see why it won't all work.  Frustruatingly, if we reset the router and remove the WPA encryption, we CAN get both computers on line via the wireless.  But it's shonky and packs up after a few minutes with one of them deciding it won't connect to the internet any more.

I'm at a loss to understand this bloody thing...
[/charlotte]

Re: 2 computers, 1 router
« Reply #7 on: 13 April, 2011, 10:42:33 pm »
One IP address isn't an issue. Most ISPs only assign you a single IP address (unless you pay them extra £) and that IP address gets assigned to the Internet facing interface of your Internet router (usually an ADSL interface but it could be  something else depending on your service). This will be a proper unique global IP address.

So now you have a router that can talk to the Internet but what about your PCs and other home devices wired or wireless that are connected to the router ?

Internally your network uses RFC1918 private addressing (or should or you can get some weird results). These addresses are in the ranges 192.168..0.0 172.16.0.0 and 10.0.0.0 and are reserved for private networks, no host or server on the Internet will use them. However you might use 192.168.1.x and someone down the street might use it and hundreds of thousands of other people all over the world might do the same so how does that work ?

The answer is Network Address Translation or NAT. When a packet goes to the internet via your router the router swaps out the source address of the packet ie your laptop or whatever's IP address with it's own address. This works fine when you have a one to one relationship between private address and public or global addresses but you normally don't you only have a single public address and lots of private addresses (PC, tablet WiFi phone etc etc),

So now we use a special form of NAT called port address translation or PAT. When you connect to something on the internet say a web server you connect from a TCP or UDP port (usually random) on your PC to the well known port of that service on the Internet server.  A web server runs using HTTP which is TCP port 80 (HTTPS is port 443) and SMTP Email is 25 and so on.
So the connection looks like this:

Your PC IP address + port 5123  ->  web server IP address + port 80

What the router does is swap out your IP address with its own and a port number of its own and then record this in a table. The web server sees an incoming connection like this:

Router IP + port 3001 -> web server IP + port 80

The router has now a table like this assuming the PC IP is 192.168.1.2 and the web server 200.4.4.6:

Local Net IP   Local Net Port    My Port         Remote IP     Remote Port
192.168.1.2         5123              3001             200.4.4.6          80

Sop when the packet comes back from the web server the router can now refer to this table to send the packet to the right internal PC (after swapping round the destination IP address).
If a second PC on the LAN tries to talk to the same web server and a third to a different one we see something like this:

Local Net IP   Local Net Port    My Port         Remote IP     Remote Port
192.168.1.2         5123              3001             200.4.4.6          80
192.168.1.3         1593              3002             200.4.4.6          80
192.168.1.7         7649              3003             87.27.1.8          443

So it doesn't matter that you have only on real IP address your router should take care of it.

First make sure each device on your local network is getting a local IP address and that they are all different.
The router normally hands these out automatically using DHCP when asked to by the devices but DHCP may possibly be configured wrong on the router.




I think you'll find it's a bit more complicated than that.

Re: 2 computers, 1 router
« Reply #8 on: 13 April, 2011, 10:46:56 pm »
Let me get this right you are using on router purely as an access point to connect wireless devices and the other as a wired internet router with no wireless on it ?

Have you disabled DHCP on at least one of them or made sure that if its on both of them that they are not giving out the same addresses and that they both give out the right DNS server and default gateway address (should be the IP address of the Internet router not the wireless one).
I think you'll find it's a bit more complicated than that.

Kim

  • Timelord
    • Fediverse
Re: 2 computers, 1 router
« Reply #9 on: 13 April, 2011, 10:49:35 pm »
Charlotte thinks this might be because we only have one IP address.

Sounds likely.

Is this an A&A supplied router?  They usually configure them properly out of the box.

How many IP addresses did you ask for?  If you've only got the one, then ask the nice guys at support to allocate you some more.  If you're not sure, log in to clueless and check the page for your line.

Or stick with the single IP address and configure your router to do NAT, which is evil, but is how 99% of home users connect to the internet (and therefore likely to be assumed to be the only way to do such things when you google or ask on forums).  192.168.whatever addresses aren't proper internet-routable addresses, and require your router to be doing NAT.

To make things even more confusing, there's the allocation issue, which is orthogonal to having correctly configured routing.  Usually this is done by the router running a DHCP server, which hands out addresses to devices on request, ensuring that there isn't any duplication (two devices with the same address on a network breaks things).  That may be not running, misconfigured or even buggy.  Though if not running, I'd expect your devices to throw some sort of (possibly vague) error when you try to connect.

I appreciate this isn't very helpful.  If I had access to your kit I expect I could work out the problem and possibly resolve it in about 10 minutes.  If you had some more specific symptoms it might be a bit easier to hazard a useful guess, but it's going to take all evening to teach you TCP/IP 101 to a level of actually *understanding* what is (and more importantly, isn't) going on.


Total stab-in-the-dark suggestion that could explain the behaviour as described: Is the router in 'bridge mode'.  Make it not be.


Pls to be posting the output of "ipconfig /all" (windows) or "/sbin/ifconfig" (*nix) from (preferably both) computers when in a working, connected, state.  That should give us something to work from.

Charlotte

  • Dissolute libertine
  • Here's to ol' D.H. Lawrence...
    • charlottebarnes.co.uk
Re: 2 computers, 1 router
« Reply #10 on: 13 April, 2011, 10:50:58 pm »
Let me get this right you are using on router purely as an access point to connect wireless devices and the other as a wired internet router with no wireless on it ?

Yes

Quote
Have you disabled DHCP on at least one of them or made sure that if its on both of them that they are not giving out the same addresses and that they both give out the right DNS server and default gateway address (should be the IP address of the Internet router not the wireless one).

I can't.  The ZyXEL router from AAISP has it all burned in from the factory and I can't change anything.

All I can alter is the Linksys one and if I take that out of DCHP, it throws a wobbler and says it can't resolve the subnet mask.

I do not know what a subnet mask is and, quite frankly, I'm loosing the will to care...

::-)
Commercial, Editorial and PR Photographer - www.charlottebarnes.co.uk

Charlotte

  • Dissolute libertine
  • Here's to ol' D.H. Lawrence...
    • charlottebarnes.co.uk
Re: 2 computers, 1 router
« Reply #11 on: 13 April, 2011, 10:53:15 pm »
Oh Gods.  This is like learning German.  I wish I understood more than about sixty percent of what you were saying, Kim.

Bridge mode; check.

"ipconfig /all" (windows) or "/sbin/ifconfig" (*nix - could be idiomatic Vulcan.  Soz.
Commercial, Editorial and PR Photographer - www.charlottebarnes.co.uk

Re: 2 computers, 1 router
« Reply #12 on: 13 April, 2011, 10:54:53 pm »
What model of Linksys do you have and is it running the original  code or have you pimped it in anyway with alternate operating systems ?
I think you'll find it's a bit more complicated than that.

Kim

  • Timelord
    • Fediverse
Re: 2 computers, 1 router
« Reply #13 on: 13 April, 2011, 10:56:42 pm »
[charlotte]
The internet facing router (provided by AAISP) is 192.168.1.1 and so is the Linksys router.  I've tried forcing the Linksys to be 192.186.2.1 and that worked, too.  But then we still had the problem of two laptops not being able to share the wireless.

Okay.  Private subnet for NAT use.  Fine.


Quote
DCHP is enabled on the Linksys (which I've told that it's no longer in Gateway mode, so it knows just to act as a wireless box for the line in from the AAISP router)

Ah, wait.  Not fine.

Hmm.

Take the wireless out of the equation and let us know what the AAISP router's doing?

I'd hypothesise that it's correctly set up to allocate a pool of real routed or 192.168.blah NATed addresses by DHCP.  You should be able to connect multiple machines to it without problems?

So you're aiming to use the linksys as a simple wireless bridge to wirelessify that LAN.  In which case it absolutely does *NOT* want to be running a DHCP server: DHCP requests will be bridged through to the AAISP box, which will happily hand out addresses from it's DHCP pool, completely unaware of any wirelessness.  Two DHCP servers, one LAN == epic fail, especially if they're handing out addresses in the wrong subnet.

That help?

andygates

  • Peroxide Viking
Re: 2 computers, 1 router
« Reply #14 on: 13 April, 2011, 10:58:36 pm »
Quote
The internet facing router (provided by AAISP) is 192.168.1.1 and so is the Linksys router.  I've tried forcing the Linksys to be 192.186.2.1 and that worked, too.  But then we still had the problem of two laptops not being able to share the wireless.

Set the Linksy one to 192.168.1.2, so it's the second item on the 192.168.1 subnet.  The 192.168.2 subnet is a whole different neighbourhood, yo.

Your PCs should pick up other numbers as they're assigned - 192.168.1.3 and so on.
It takes blood and guts to be this cool but I'm still just a cliché.
OpenStreetMap UK & IRL Streetmap & Topo: ravenfamily.org/andyg/maps updates weekly.

Kim

  • Timelord
    • Fediverse
Re: 2 computers, 1 router
« Reply #15 on: 13 April, 2011, 11:00:32 pm »
Oh Gods.  This is like learning German.  I wish I understood more than about sixty percent of what you were saying, Kim.

Back in the day, I learned how to use ipchains using nothing but the German man pages.  I didn't have access to the internet to dogpile for help until I'd worked out how to get it to do NAT.

That's probably why I failed my engineering degree, actually.


Quote
Bridge mode; check.

On what?  I wrote that first post unaware that you had two routers.


Quote
"ipconfig /all" (windows) or "/sbin/ifconfig" (*nix - could be idiomatic Vulcan.  Soz.

Things to type in at the command prompt that will invoke meaningful geek-spew that you can paste here to enlighten us as to what's going on.

tonycollinet

  • No Longer a western province of Númenor
Re: 2 computers, 1 router
« Reply #16 on: 13 April, 2011, 11:00:48 pm »
If you have the linksys set to 192.168.2.1 this probably will not work. It is on a different subnet to your aaisp router.

If your AAISP is 192.168.1.1 then normally  you will have valid addresses on your network from 192.168.1.2 to 192.168.1.254

If the AAISP router is doing DHCP, then you need to turn it OFF on the linksys - otherwise they'll hand out identical IP's and bugger up your network. You'll also need to set the linksys address to one the DHCP is not handing out. If you cant change the DHCP range, then set it to ...254

The other option is to set up all your PC's to have fixed IP addresses in the range given above - but then you'll need to manually enter the DNS server addresses as well.


Alternative 3 - can't you use the linksys to connect to AAISP? I have a BE special router, but don't use it.


EDIT - it sounds very much as though your PC's are being given the same IP address.

Kim

  • Timelord
    • Fediverse
Re: 2 computers, 1 router
« Reply #17 on: 13 April, 2011, 11:03:24 pm »
Note for the helpful but unfamiliar with AAISP: an AAISP supplied router is highly likely not configured to use NAT and RFC1918 addresses.  They do real routing wherever possible.  Don't make assumptions.

Furthermore, sticking a Linksys in NAT mode behind it would be like sticking knobblies on a titanium road bike.

tonycollinet

  • No Longer a western province of Númenor
Re: 2 computers, 1 router
« Reply #18 on: 13 April, 2011, 11:08:20 pm »
OK - unusual compared with most ISP's

Does that still work with DHCP? IE does the router know what address are available and hand them out to connected devices? Or must they then be set up manually?

Kim

  • Timelord
    • Fediverse
Re: 2 computers, 1 router
« Reply #19 on: 13 April, 2011, 11:10:21 pm »
OK - unusual compared with most ISP's

Yes.  That's why we use them.


Quote
Does that still work with DHCP? IE does the router know what address are available and hand them out to connected devices? Or must they then be set up manually?

It should be configured to allocate the real IP addresses to the LAN by DHCP out of the box, yes.  They set them up for the customer's connection before sending them out.

Re: 2 computers, 1 router
« Reply #20 on: 13 April, 2011, 11:10:43 pm »
NATs OK saves address space. There isn't enough address space for most ISPs to hand out real addresses like smarties. Well not until we all move to IPv6 anyway.

No reason not to use NAT for home use.
I think you'll find it's a bit more complicated than that.

Charlotte

  • Dissolute libertine
  • Here's to ol' D.H. Lawrence...
    • charlottebarnes.co.uk
Re: 2 computers, 1 router
« Reply #21 on: 13 April, 2011, 11:12:58 pm »
Note for the helpful but unfamiliar with AAISP: an AAISP supplied router is highly likely not configured to use NAT and RFC1918 addresses.  They do real routing wherever possible.  Don't make assumptions.

Furthermore, sticking a Linksys in NAT mode behind it would be like sticking knobblies on a titanium road bike.

So we've got kickarse internet, but we can't use two computers at once?

So how do we do this then?  Do we need a new, better wireless box?  the Linksys WRT54GL was the best I could find when I bought it 18 months ago.
Commercial, Editorial and PR Photographer - www.charlottebarnes.co.uk

Kim

  • Timelord
    • Fediverse
Re: 2 computers, 1 router
« Reply #22 on: 13 April, 2011, 11:14:59 pm »
NATs OK saves address space.

But adds layers of complication, as this thread demonstrates.


Quote
There isn't enough address space for most ISPs to hand out real addresses like smarties.

There isn't enough legacy IP address space left for anyone to hand them out like anything.


Quote
No reason not to use NAT for home use.

Various reasons, none of which have been compelling enough to prevent it becoming a de-facto standard way of doing things, unfortunately.   :(

Kim

  • Timelord
    • Fediverse
Re: 2 computers, 1 router
« Reply #23 on: 13 April, 2011, 11:18:12 pm »
So we've got kickarse internet, but we can't use two computers at once?

Sure you can, it's just a matter of working out how...


Quote
So how do we do this then?  Do we need a new, better wireless box?  the Linksys WRT54GL was the best I could find when I bought it 18 months ago.

Plz to be establishing that everything is working as intended with the AAISP router before bringing the linksys and wireless into the equation.

Then try and work out how to persuade the linksys into being a simple access point.  It should be possible, but if your router isn't configured properly, then you won't have a clue where the problem is.

tonycollinet

  • No Longer a western province of Númenor
Re: 2 computers, 1 router
« Reply #24 on: 13 April, 2011, 11:20:31 pm »
Note for the helpful but unfamiliar with AAISP: an AAISP supplied router is highly likely not configured to use NAT and RFC1918 addresses.  They do real routing wherever possible.  Don't make assumptions.

Furthermore, sticking a Linksys in NAT mode behind it would be like sticking knobblies on a titanium road bike.

So we've got kickarse internet, but we can't use two computers at once?

So how do we do this then?  Do we need a new, better wireless box?  the Linksys WRT54GL was the best I could find when I bought it 18 months ago.

Changing the wireless box won't help - you still need different IP's for the machines, no matter how they connect.

I would suggest short term (if it is possible) connecting with the linksys using NAT like you used to do. I am assuming that AAISP connections are sufficiently standard to allow this. Go for non nat, when AA have given you some additional IP's. Bear in mind (if you are not using NAT) you will need enough IP's for every device you want to have net access for - pc's, game consoles, phone, ipads, visitors etc etc.

Or do AAISP allocate IP address dynamically as you need them??  :-\ have to admit I'm a little in the dark with this method of connection - think I'll shut up till I know more.