Pls see my answers below.
Thank you very much for your kind help and time.
-keevill-
>In my network I have about 50 client machines all running WinXP with USB
>wireless adaptors.
Oh-oh.
>For wireless connection in the office there are 5 Wireless router/ADSL
>modem
>/ Switches all connected via RJ45 cable to each other ( daisy chain ) into
>the network in order to increase the coverage of the wireless network.
Ummm... I suspect you really have *ONE* wireless router/ADSL
modem/switch, and *FOUR* wireless access points, or wireless routers
with the router section disabled and the DHCP servers turned off. If
these boxes are all identical and have ADSL modem sections, then you
have a "double NAT" configuration, which methinks is a rather bad
idea.
Actually, upon checking once more since the network has grown over the last
year or so, it appears that I have got 4 ADSL modem / routers and 1 straight
wireless access point. Therefore, I fulfill your assumed 'rather bad idea'
scenario.
I have not discovered where to 'turn off' the WAN or modem aspect. I have
merely not configured it on the 3 which are not being used to connect to the
ADSL ISP.
Could I trouble you for the manufacturer, model number, and a better
description of how you have this pretzel wired?
They are all SMC Barricades SMC 7904 type boxes each one wired back to the
ADSL Modem/Router via RJ45 hard wired connections.
>I have configured 3 of them with DHCP each on different ranges.
>192.168.0.30-50 for one - 192.168.0.100-150 for another and so on.
That will work but is largely un-necessary unless you a filtering
broadcasts through each access point. That will be the case if you
have the router sections enabled and are doing double NAT. Can you
give a better description of the wiring and IP layout?
I am not sure what you mean here by the filtering . I am not consciously
doing this. The router sections are of course enabled and being used .
The 'main ADSL Router Modem' is used as the principal 'hub/switch' with 4
RJ45 cables connected from it to the the other access points. Each of these
are set up in different areas of the office in order to give more wireless
coverage to the network. Of course you are right, I could in turn run up to
4 hard wired lan connections from each of these to close proximity machines
in order to cut down the wireless traffic. I have not done this since I
thought I would avail myself of the convenience of wireless.
>The others are not configured with DHCP .
I'll assume that means you don't have the DHCP server enabled on the
LAN side.
Yes that is correct.
>Some machines are on fixed IP and
>others are configured to obtain IP via the DHCP routers.
>Internet connection is via ADSL .
>I have learned that some machines which are configured to obtain IP and DNS
>settings auto, work with good connection to Internet and others do not.
>It suits me to have some areas on DHCP for guests who need to connect and
>it's easy to just let them take the default of obtain IP & DNS
>automatically.
Without a VLAN, they're going to get the same IP's and DNS servers as
everyone else.
>Sometimes although a PC connects to an access point on DHCP with a range of
>192.168.0.30-50 for example, it obtains an IP address of 192.168.0.125
>which
>is clearly not right. and when this happens the Internet connection is lost
>since the DG is not discovered.
Yep. That's why you really should only have one DHCP server per
network. The mechanism is fairly simple. A random client gets an IP
from DHCP server #1. The client then moves out of range of this
wireless router and DHCP server and blunders into the area serviced by
a different wireless router and DHCP server. Things continue to work
normally until the DHCP lease expires and the client tries to renew
it. Since it can't directly contact the original DHCP server, it
fails and grabs a new lease from the 2nd DHCP server. It would all
work fine except that Windoze XP and I suspect (not sure) Vista have
the irritating habit of sometimes not also updating the default
gateway IP. I've seen it a few times but have never bothered to
troubleshoot the problem. A simple:
ipconfig /release
followed by a:
ipconfig /renew
will solve the problem, at least until the next time the DHCP lease
expires.
OK that is clear and that's a clear and logical explanation.
However, my concern was that if a machine in the local proximity of a router
without DHCP connects, then how can it obtain an IP address if that router
does not act as a DHCP server?
That's why I thought I would need to configure each one of them with DHCP
server powers.
Is there some way that the machine can query the whole network and
'discover' another router along the route which is THE 'approved' DHCP
server on the network and grab an IP from that router??
I have one further thing to advise you of my configuration.
I have configured a couple of the routers with a static route. In this
configuration.
0.0.0.0 ----- 0.0.0.0--------- 192.168.0.3 ( where this address is the
address of the Modem/Router. I have discovered that if I do not do this,
then whilst I can connect to the LAN, I cannot access the Internet.
Incidentally, if you have Vista machines, there are a few assorted
DHCP bugs that have to be dealt with manually until SP1 arrives.
<http://groups.google.com/group/alt.internet.wireless/msg/52ee76bb33f98ac4>
>Many times I have to restart/reboot the routers in order to regain
>connection.
>Is there something inherently wrong with my configuration which causes
>this?
Yes, but from your description, I can't tell what you have for
hardware and topology.
What you should be doing is something like this:
ADSL
Modem ===== Router ==== wireless 1
==== wireless 2
==== wireless 3
==== wireless 4
==== wireless 5
The modem, router, and wireless 1 are all in the same box.
The 4 "wireless" boxes are plugged into the LAN ports.
The router should be 192.168.1.1 and have the DHCP server enabled.
It should be the only DHCP server in the system.
The various "wireless" devices are being run as access points. That
means that if it happens to be a wireless router, then nothing is
plugged into the WAN(internet) port and the DHCP servers are all
disabled. The management interface should be 192.168.1.2 thru
192.168.1.5 for each access point. The wiring can be daisy chained
for convenience, but that makes troubleshooting (watching the flashing
lights) and monitoring (sniffing) somewhat awkward.
So actually, in order for me to get to your suggested situation, I just have
to stop the DHCP servers on all but the Modem/Router and give a sufficiently
large band of IP addresses on this to accommodate all the users.
However, it makes me ask how can the users which connect to the access
points get IP addresses from the DHCP server which is unreachable directlyl?
Can the system be able to detect the DHCP server automatically?
I suspect the answer is YES and that's the area of my lack of knowledge
which has caused me to configure multiple DHCP servers.
If you're trying to do something special for "guest" machines and
visitors, I usually suggest that you get a completely separate router
and wireless device for their use, that never hits the inside LAN at
any point. I find this method easier and cheaper than dual SSID's.
However, if your unspecified equipment can handle dual SSID's, that's
the way to deal with guest devices.
Diversion: Reading between your lines, you have 50 desktops connected
with USB wireless devices. That's a rather large number of wireless
devices to be running in a small area. I suspect that some of these
desktops could instead be connected via CAT5, which will take the load
off the wireless and possibly reduce the number of access points.
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