IP range problem

[quik1]

Hey all. I have this IP problem
My pc`s are set to automatically get an ip. If the ip`s that it gets start with "10.0.x.x" then the internet works, but if it gets a ip that starts with "192.1xx.x.x" then there is no internet. The network still works, but just no internet.
Any ideas.

 

[Peon]

You have another router or device on the same network.

Most probably you have an ADSL router and also a wireless access point. the ADSL is giving out the 10.0 addresses and the wireless device is giving out the 192.1 addresses. You will need to disable the DHCP on the wireless device or set your pc's or laptop to static ip's.

 

[ambo]

A Windows PC setup with internet connection sharing could also be the cause of the rogue DHCP on your network.

 

[Pada]

Basically you have 2 DHCP servers on your LAN segment, where the one who is handing out 192.168.x.x IP addresses should be disabled.

If its a 192.168.137.x IP address, then it is DEFINITELY Windows' Internet Connection Sharing.

 

[quik1]

There are 70 pc`s in the network and 1 adsl router. All win xp. Any simple way to figure out the internet connection sharing. Will that be on 1 of the pc`s?

 

[Pada]

Windows XP's ICS will hand out 192.168.1.x IP addresses.

You can run Wireshark and then monitor UDP Port 68 to determine the MAC address & possible IP address of the DHCP server(s).

Hopefully you've manually registered all MAC addresses on your DHCP server, otherwise you'll have to check each PC.

 

[Tinuva]

Actually its easier. When one of the pcs get a 192.168.x.x IP, just check to what IP the gateway points to, and go into that pc and fix it.

 

[quik1]

If i plug a pc directly into the ruouter the internet still doesnt work unless it has a 10.0.x.x ip.

 

[Pada]

quik1: that is because the Windows' Internet Connection Sharing is giving you the wrong IP before the router's DHCP server has a chance to do it.

 

[MVGL]

@OP - What are you doing fiddling with a 70 + Netowork when you don't even know what DHCP means - just my thought. :wtf:

 

[MVGL]

@Pada - A network this size should not be using the "weak" Internet Connection sharing. Come on

 

[MVGL]

This is one of those candid camera moments ... right

 

[Pada]

yup @ MVGL. A network of that size should have a DHCP server with each MAC address registered manually, and I'm also not sure why quik1 is trying to diagnose it when he knows so little.

 

[Tinuva]

Well its actually easier to segment that network up into separate vlans, then the issue won't affect the whole network but only the affected vlan. Manual DHCP address registering is just too much work, people should create less work for themselves, not more.

At least with vlans it is also easier to find the problem when it only affect 10 pcs or less, but 70 or more...that is indeed a nightmare.

 

[Pada]

Ja, but you need to know something about networking to work with VLANs + you require managed switches for that, which can be quite expensive.

 

[Tinuva]

Really? My cheap billion modem can do a different vlan for each port, easy and cheap way to get 4 segments on your network.

 

[Pada]

Ja Tinuva... you do get cheap hardware that supports VLAN's, but in general the 16/24/32 port switches with VLAN support aren't cheap.

Like my D-Link 2100AP, Buffalo & MikroTik hardware all supports VLAN's.

 

[quik1]

I plugged my laptop (with a 192.x.x.x ip) into my router at home and it works, but when i plug it into the router on the network (nothing else plugged into it - just the laptop) it doesnt work.
@mvgl - yes my network experience is limited (compared to some of you guys), but thats why im asking. I setup another network with 1 router, 60 pc`s, 2 servers and it worked without a problem.
I just cant understand why this router isnt working. i tried a different router and it does the same thing

 

[Pada]

quik1: it would seem as if it doesn't work, because there is another DHCP server on your network that is handing out you the wrong IP address & gateway.

I would suggest that you disconnect 1 switch at a time from the router and that way you try and eliminate on which switch that DHCP server is running. Each time you disconnect a switch, you'll have to release your IP address and renew it with 'ipconfig /release' & 'ipconfig /renew'.