Modem / Router / DNS problem - Sorted TY all

[Steve Maskery]

Hi all,
Any network gurus here?

We had a new cable modem yesterday.

1 PC works (has internet access) when connected directly to cable modem.
2 PC works when connected wired through router.
3 Laptop works when wire directly to cable modem.

BUT

4 Laptop cannot access internet when connected wirelessly. It says it is connected to the Home Network, and I can browse to the router and access the admin menus, but I can't get beyond that. My desktop does not appear in the list of machines on the network, just the laptop.

I ran a diag test and it is complaining about the DNS servers. My desktop is set to acquire DNS addresses automatically, the laptop WAS set to the IP address of my router. I've changes that to auto too, but still nothing. How can I ensure that DNS is working?

Any ideas? Virgin run a premium rate phone line, they keep me on for 10 mins and then say they can't fix it and it's not their problem anyway!

All was fine until we changed the cable modem.

Any help gratefully received.

Cheers
Steve

 

[christoph clark]

You don't mention if it's xp your using..

If your using XP when you go to the TCP/IP properties to change the IP address, it is by default set to Obtain IP Automatically and the DNS Server is also set to Obtain DNS Automatically.
When you change from 'Auto IP' to 'Use The Following IP', it also changes the default DNS setting from 'Auto DNS' to 'Use The Following DNS'.

Leave the DHCP Start and DHCP End address where they were (192.168.1.15 to 192.168.1.47 in my case).
Assign a Static IP address outside this DHCP range (like 192.168.1.100).
Don't forget to assign the DNS Server as well (192.168.1.1 in my case).

Might help.

 

[christoph clark]

To add to my last comment. Are you sure it's a computer router your using. :lol: :lol: :lol: :lol:

 

[Argee]

It could be that your router is using Mac filtering. In the admin pages for your router, look at "Wireless Settings" and see if there's an option to add a device manually. If there is, it will usually have 6 boxes for the Mac address (physical address) to go in, plus a name for the device of your choosing.

To find the physical address of your laptop, run "command" (no quotes) to bring up a DOS window, then type "ipconfig /all" (again, no quotes) and press enter. You should see your laptop name and the physical address. Enter these as apporpriate, click on "Apply" or "Save." Type "exit" (no quotes) to quit the black DOS window. Retry.

If no joy, on your PC, do the same command, etc. as above, look for the DNS server address(es) on your PC and note them. Type "exit" (no quotes) to quit the black DOS window.

Now, back to the laptop and go to Network Connections, then select your "LAN connection" and "Properties." Click on "Internet Protocol (TCP/IP)" and then "Properties." Enter the DNS server address(es) in the relevant box(es) and see if that helps. If not, return to "Automatic" settings.

Let us know the make and model of your router if that doesn't work, plus what OS(es) you're using on the PC and laptop.

Ray.

 

[Steve Maskery]

Thanks guys

XP on both PC and Laptop.

Router is an MSI RG54G3.

Something else strange is going on. I can access the router from the laptop instantly, but not at all from my desktop, which is wired to it, even though I can surf fine. It does not ping.

The laptop is in the MAC list on the router and I've set thelaptop setting to acquire IP address auto, but use Virgin's DNS servers, obtained from my desktop settings.

But still no joy

S

 

[Fecn]

Most cablemodem services are restricted to talk to only a single MAC hardware address (e.g. only one device). Does your router have the option to do NAT network address translation so that you can hide the rest of your hardware behind it?

 

[momo]

You may also have to change its workgroup name to match the other workgroup the rest are on.

for some reason my loft pc didnt see the network till it was on the same workgroup as all my other machines.

 

[Argee]

Something else strange is going on. I can access the router from the laptop instantly, but not at all from my desktop, which is wired to it, even though I can surf fine. It does not ping.

I'm not clear what "does not ping."

Can you ping the router from the laptop?
Can you ping the PC from the laptop?
Will either the laptop or the PC ping itself?

The router may not allow more than one machine to access it at a time (more than one admin account on-line). I'm assuming that the Workgroup hasn't changed, as they all worked OK until the recent modem change?

Ray.

 

[Steve Maskery]

Hi Ray

The laptop can ping the router but not the desktop
Both machines can ping themselves but not each other
The desktop will not ping the router, even though I am typing this through that connection.

Everything was fine until the new cable modem.

I'm considering re-installing the wireless network from scratch, but it's years since I've done that, and if I screw up, it's bye-bye...

A very unhappy Steve.

 

[Steve Maskery]

Most cablemodem services are restricted to talk to only a single MAC hardware address (e.g. only one device). Does your router have the option to do NAT network address translation so that you can hide the rest of your hardware behind it?

No idea, how do I find out?
S

 

[Fecn]

Further to my one-mac-address comment above - I've found it necessary to power-cycle cable modems before they will talk to a different MAC address. If you've plugged your desktop machine into the cablemodem then the cablemodem won't talk to anything else until you switch it off an on again.

I've looked at the specs for your router and it says it will do one-to-many NAT which is just what you need. You should have your router handing out DHCP information to the laptop and desktop machines and then doing address translation to talk to the cablemodem. The cablemodem should only be connected to the router and the router needs to learn it's IP address from the cablemodem.

HTH

 

[Fecn]

In terms of IP addresses, here's what I'd expect...

Your router hands out IP addresses like 192.168.x.x to the desktop or laptop machines. - The network 192.168.x.x (and also 10.x.x.x and 172.16.x.x) are reserved for private networks and don't get passed across the internet.

Your cablemodem hands out addresses which aren't starting with 192, 10 or 172. My virgin cable broadband address starts with 84.6.x.x

If your laptop and desktop machine addresses don't both start with the same bit (e.g. both should be on the 192.168.x.x or another private one) then they won't be able to talk to each other.

Your router's job is to pretend to the cable modem that internet traffic from the computers on the 192.168.x.x network are actually coming from the 84.6.x.x address that your cablemodem gave out, so your cablemodem only has to talk to one device and deal with one address.

HTH - Your addresses may be different to mine.

 

[Rich]

Hi Steve, my laptop is connected wirelessly to the router, but my 2 lads pc's upstairs are wirelessly connected through dongles, could this be your solution?
regards
Rich.

 

[Steve Maskery]

Fecn
Well yes, that is my understanding too, and indeed that is what I think I have, which is why I don't understand.

Cable modem address: 82.5.x.x
Router address: 192.168.1.254
DHCP Enabled 192.168.1. 100 - 199
Desktop NIC appears to be 82.5.x.x

Does this mean it is getting its IP address from the cable modem and not from the router? Is this why it connects and the laptop doesn't?

The default gateway for the desktop is 82.5.56.1. Shouldn't it be the 192.168.1.254 of the router? I'm getting very confused. And hungry.
S

 

[Argee]

The laptop can ping the router but not the desktop
Both machines can ping themselves but not each other
The desktop will not ping the router, even though I am typing this through that connection.

The problem, therefore, is between your PC and the router. Reboot the router, then the PC, then try again.

Ray.

 

[Steve Maskery]

Done that.

I changed the PC IP address to 192.168.1.1 manually. I could access the router instantly but lost internet access. The only way I have got this back is to reset it as auto, and it has gone back to being 82.5.x.x address, i.e. assigned by Virgin. It's as if ithe PC is ignoring my router and going straight for the cable modem, and the laptop, which sees the router fine, isn't getting beyond that.

S

 

[Argee]

Flippin' computers!

So, to summarise, when your laptop sees the router it can't surf, when your PC sees the router it can't surf. PM me the IP addresses you've gathered and I'll try to ping from outside your network and report back.

I'll have a mess around with my system and see if I can reproduce something similar. Get something to eat!

Ray.

 

[Steve Maskery]

Thank you all, very, very much.

It appears to be sorted. I say "appears" because I don't understand what I've done to fix it. The settings are ones I'm sure I've had before.

I don't care, it works. Now then, I've got a day's painting to catch up on.

Happy Steve