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Limited or No Connection

Posted on 2007-10-19
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I would appreciate any help that I can get.  I normally do not get too involved with the network side of things, just desktop support.  But I am working at a client that has a Windows 2000 server and maybe 15 to 20 clients the log into the domain.  They also have a wireless Access Point that is used for about 10 tablet pcs to connect only to the internet. They do not log onto the domain and do not have access to the server, shares or printers.  Recently, some of the tablets are not connecting and giving me a limited or no connection Icon.  I powered up another wireless router just for test and all the units can connect to that with out a problem.  I even replaced the ACCESS POINT and now a different batch of tablets do not connect now.  My questions are as follows.

1.      Do the number of client licenses have anything to do with computers that are not actually connecting to the domain? I dont think so, but wanted to double check.
2.      I noticed an error about running out of IPs on the server screen a one point?
3.      I have also seen an IP conflict error on the server at times?

Settings are as follows:

Main Cable Router with DHCP OFF = 192.168.1.2
Server IP = 192.168.1.3
Access Point = 192.168.1.5

If I run an IPCONFIG on a working tablet unit I get:
IP = 102.268.1.63
Subnet = 255.255.255.0
Default Gateway = 192.168.1.2
DNS = 192.168.1.3

Please, what am I missing here other than a good understanding of networking?
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Question by:waytron
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by:dlangr
ID: 20111791
the dhcp server seems to be out of available leases, wich is why you would get an ip like that.... increase the amount of available leases on the dhcp server
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by:dlangr
ID: 20111826
i misread the ip, but i think i am still right about running out of leases
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by:dlangr
ID: 20111849
IP = 102.268.1.63 in you comment should have been 192.168.1.63 i think
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by:dlangr
ID: 20111900
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by:dlangr
ID: 20111915
I must be sleepy, if they don't connect to a server and are not domain members, they won't need the client access licenses.
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Fred Marshall earned 1000 total points
ID: 20112453
I can't tell from your description how many devices are running DHCP.  Surely the wired computers would have it accessible, right?  Then, the wireless computers as well - via the access point?

It's important to have a couple of things straight:

1) The DHCP address ranges between DHCP servers don't overlap.

2) There are enough DHCP addresses available in the range to provide for more than the number of computers on the network at any one time - because one can pick up a lease, leave the network but hold the lease hostage for some time.  So, when another computer is turned on, it needs an address too!  This implies enough addresses for the total number of computers that will be connected (or connected and turned on) during some period of time and *not* only the number of computers that will be connected at any instant in time.

After that, if there are IP address conflicts then are there any devices with static IP addresses that might interfere with the DHCP ranges?  For example, the access point is 192.168.1.5.  It would be imporant that this address not *also* be in a DHCP range.  Another example, if a computer has an IP address that's static or perhaps with an unexpired DHCP lease - and it's turned off - then another computer could be assigned the same address if its address is in the DHCP range.  Then, when this first computer is turned back on, there will be a conflict.  Knowing if any of the computers has a static IP address could be a chore depending on how many there are!
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by:waytron
ID: 20113297
Yes that IP was an error, it is 192.168.1.63.
I am at home now, but if I recall the DHCP server was set to give out 50 IP adresses between 192.168.1.20 and 70.
The  only DHCP server is  the Windows 2000 server.  DHCP on the main router is off.
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by:dlangr
ID: 20114213
Now that i think about it, you might be running into the limitations of the wireless router to support that many clients.

Use both routers and if needed, use a third router.

They should all be on separate channels to eliminate channel to channel interference. Channel 1, 6 and 11 have the most separation.

Give them the same ssid and key and the clients will roam between them automatically.
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by:dlangr
ID: 20114215
The amount of clients that can be supported depends on the wireless router(s) used.
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by:waytron
ID: 20114375
I am NOT using a wireless Router.  It is just a Linksys WAP11 Access Point.  I always thought you could have up to 255 clients on any wireless routers.  Well in any case, when I was playing with it last night I only had 5 Tablets turned on and the same 2 would not connect.  If the number of units was an issue, as I turned off units, wouldn't other units then be able to connect.
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by:waytron
ID: 20114414
I am thinking out load here.  I am going over to play with this network this morning.  Could I just replace the Access point with a Router with the IP Set to 192.168.1.5.  And let it hand out IP addresses to the tablets instead of the server doing this.  I this right?
Set the router to 192.168.1.5
Default Gateway to 192.168.1.2
DNS to 192.168.1.3
Set the DHCP on the router to a range outside the range handed out  by the Server
OR could I change the router DHCP to something different like 192.168.2.1 thru 192.168.2.100
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by:dlangr
dlangr earned 1000 total points
ID: 20115085
> If the number of units was an issue, as I turned off units, wouldn't other units then be able to connect.
Yes they would.

but you said:

> even replaced the ACCESS POINT and now a different batch of tablets do not connect now.

Wich is why it led me to beleive the router might not be able to cope the amount of clients.

If the same clients keep having the problem, there might be a shortage of free leases. You should check the dhcp server to see how many leases are given out. Leases can be kept in use for quite some time before they expire, even after a client disconnected. This depends on how the dhcp server is configured. Check the leases to see if they are not all given out. Also check if no other device like servers/printers/workstations/routers are using statically assigned ip's that are in the range defined in the dhcp server.

Regarding your thinking out loud:
You don't want 2 different dhcp servers on the same network. You can disable the dhcp server on the w2k server and enable it on a router to see if the issue lies with the dhcp server you are using at the moment. Even setting the DHCP server on the router to a different range won't prevent the 2 DHCP servers from answering clients that you did not want them to.

If you don't want to disable the dhcp server on the w2k server, then you would need to seperate the setup from the network the w2k server is on to make sure it won't answer the dchp requests, or disconnect the w2k server from the network.








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by:waytron
ID: 20115414
You say the router can not handle the number of Clients. This sysem has been in place and working fine for over 5 years this way. They have not added any new clients that I know of.
Well, I just got back from working on the network.  All seems to be working. Although I am not sure if it is correct or not.
I replaced the Access Point with a Wireless Router.
Settings as follows:
Static IP of 192.168.1.5 (same IP as original AP)
Subnet 255.255.255.0
Gateway 192.168.1.2
DNS 192.168.1.3

Network Lan Side
Local IP 192.168.2.1
DHCP 192.168.2.100 thru 149

So now this router is handling service to all the tablets.
Now everything seems to be connecting just fine. The tablets all have internet access and all the regular Desktop Clients are working  as well.

Why do you say that I don't want 2  DHCP servers on the same network.  These tablets only need internet access and nothing else.  
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by:Fred Marshall
ID: 20116477
> If the number of units was an issue, as I turned off units, wouldn't other units then be able to connect.

Not necessarily.  See my earlier post.  It's not "the number of units" so much as "the number of DHCP addresses".   I suggested the number of addresses should be greater than the total number of units (whether they are off or on / present or not present / etc.)
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by:waytron
ID: 20117503
When I was in there yesterday, I checked the DHCP settings on the server and it was set to hand out IP addresses in  the range of 192.168.1.10 thru 192.168.1.94.  The total number of hardwired workstations is 24 and they have about 22 tablets but there are never more than 7 in the building at any one time.  I guess I will see Monday when everyone is back, if everything is working correctly.
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by:dlangr
ID: 20118650
I did not say it does not support them, just opted that there might be a limit to how many clients it does support. i did not know at that time, wich router you are using.

I said you don't want 2 dhcp server on the same network, because they would then both react to dchp requests, with somethimes the server and sometimes the router winning the battle to answer first. This would mean:

With both server serving a different range: some clients would get ip's from 1 range, some from the other.
WIth both server serving the same range: You will get ip conflicts because 1 server will not know which ip adresses are given out by the other server.

Usually, this is not something you would want.

But, as you said in your last comment, the wireless router is now routing 192.168.2.x  to 192.168.1.x, wich is fine as then the dchp broadcasts would only reach the dhcp server on the router as they will not be routed to the 192.168.1.x network. So that will work.
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by:waytron
ID: 20119154
I really appreciate your responses here.  I am not sure that I really understand the problem.
Have I not really created 2 seperate networks here.
I have the hard wired network that the Server is handing out IP's from 192.168.1.10 to 192.168.1.94 and then attached to that network at 192.168.1.5, I have a wireless router that is servicing all the wireless tablets and handing out IP's in the range of 192.168.1.100 to  192.168.1.149.
I don't see the conflict here.  What am I missing?
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by:Fred Marshall
ID: 20124455
The DHCP ranges are as they should be - no conflict.

But, just to add some insight:

Is the wireless "router" being used as a "router" or as an "access point" or "switch"?  If a router then there would typically be a connection to the WAN/internet port.  If an access point or a switch, then tere would typically be *no* connection to the WAN/internet port - but rather a wired connection to the LAN side.  If a router, then there might be network address translation (NAT).  So, it sounds like it's an access point or switch.

I say "switch" because if you ignore the fact that the connections are wireless, the box acts just like a switch in the network architecture.  This leads one to ask: "Why are there two DHCP servers at all?"  

Here is  a configuration that should work:

Plug the wired LAN into the LAN side of the wireless "router".
Turn off DHCP on the wireless "router".
Then, wireless connections should seek addresses via DHCP and will get them (through the switch/wireless router) from the wired router.
Certainly no confusion with that sort of arrangement.

Then, you may wish to expand the DHCP range on the wired router.  
Did anyone mention DHCP lease times?  What are they?
If the lease times are too long then it might be possible to exhaust the available addresses as machines come and go.  In a commercial environment with a dynamic situation you might set the lease time at something like 8 hours.
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by:waytron
ID: 20144129
Thank you both for you information and insite.  The network is working perfectly now.  The wireless router is handling the tablets jsut fine and the server is handling all the wired desktops.  Thanks again.
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