In my network I have about 50 client machines all running WinXP with USB wireless adaptors. 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. 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. The others are not configured with DHCP . 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. 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. 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?
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.
Could I trouble you for the manufacturer, model number, and a better description of how you have this pretzel wired?
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'll assume that means you don't have the DHCP server enabled on the LAN side.
Without a VLAN, they're going to get the same IP's and DNS servers as everyone else.
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.
Incidentally, if you have Vista machines, there are a few assorted DHCP bugs that have to be dealt with manually until SP1 arrives.
Yes, but from your description, I can't tell what you have for hardware and topology.
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.
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.
Pls see my answers below. Thank you very much for your kind help and time.
-keevill-
Oh-oh.
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.
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.
I'll assume that means you don't have the DHCP server enabled on the LAN side.
Yes that is correct.
Without a VLAN, they're going to get the same IP's and DNS servers as everyone else.
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.
Yes, but from your description, I can't tell what you have for hardware and topology.
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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