dhcp server question

[-keevill-]

I have what I believe to be a very simple question.
On my office network I have 4 wireless routers each one hard wired into the
main office router and each one serving a different area in the office. I
understand that it is bad procedure to have more than one dhcp server even
if I configure each one as dhcp servers on different IP ranges.
Therefore, if I configure just one of these wirless routers as dhcp, will
clients be able to get connected even if they are connecting to router in
their area which is NOT the network dhcp server?
Will they be able to discover an IP address from the server even though they
do are not able to reach it ?
So far, I am having intermittent success with this.
Why can I not set up each router as dhcp servers but using different
non-conflicting IP ranges ?



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Posted via a free Usenet account from http://www.teranews.com

[Jeff Liebermann]

"-keevill-" <keevill@gmail.com> hath wroth:

>I have what I believe to be a very simple question.

That doesn't mean that the answer will be simple.

>On my office network I have 4 wireless routers each one hard wired into the
>main office router and each one serving a different area in the office.

Are these wireless *ROUTERS* or are they *WIRELESS ACCESS POINTS*?
Better yet, kindly disclose the maker and model numbers.

>I understand that it is bad procedure to have more than one dhcp server even
>if I configure each one as dhcp servers on different IP ranges.

Yep. You can get away with it by using non-overlapping IP blocks and
a large netmask, with a common gateway IP. However, there are a few
situations where it will screwup. For example, if the client roams to
a different wireless router, and then tries to renew the DHCP lease,
it will fail because the lease can only be renewed by the DHCP server
that originally issued the lease.

>Therefore, if I configure just one of these wirless routers as dhcp, will
>clients be able to get connected even if they are connecting to router in
>their area which is NOT the network dhcp server?

No clue or guess. Kindly disclose the maker and model numbers along
with the topology (wiring and interconnections). There are several
ways to configure such a system. Some will work, some will not.

Why don't you have the "main office router" act as the DCHP server?
That way, you don't need wireless routers and can use wireless access
points.

>Will they be able to discover an IP address from the server even though they
>do are not able to reach it ?

No clue. I need to know the hardware and topology.

>So far, I am having intermittent success with this.

Intermittent success is not very successful. My guess(tm) is that
your clients are roaming to different wireless routers, which is
causing problems.

>Why can I not set up each router as dhcp servers but using different
>non-conflicting IP ranges ?

You can. You just can't roam between access points with such an
arrangement. If you have all your wireless routers set for the same
SSID, you won't even know if a client has roamed until it tries to
renew the DHCP lease, and fails.

In case you missed it.... Make, model, harware version, topology, etc.



--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[-keevill-]

They are wireless routers SMC2904wbra2
All have different SSID's
They are wired with RJ45 cables running from an initial Router ( same make
and model ) which itself is connected to the ADSL Internet connection.
I think it's fair to say very simple topography.
There should be no need for PC's to roam between routers but of course some
will be able to contact 2 routers.
Hope that's enough for some ideas of best way to manage things.



"Jeff Liebermann" <jeffl@cruzio.com> wrote in message
news:s2ips3pt42tiktj6a5pklj4hgmmccmfrm0@4ax.com...
> "-keevill-" <keevill@gmail.com> hath wroth:
>
>>I have what I believe to be a very simple question.
>
> That doesn't mean that the answer will be simple.
>
>>On my office network I have 4 wireless routers each one hard wired into
>>the
>>main office router and each one serving a different area in the office.
>
> Are these wireless *ROUTERS* or are they *WIRELESS ACCESS POINTS*?
> Better yet, kindly disclose the maker and model numbers.
>
>>I understand that it is bad procedure to have more than one dhcp server
>>even
>>if I configure each one as dhcp servers on different IP ranges.
>
> Yep. You can get away with it by using non-overlapping IP blocks and
> a large netmask, with a common gateway IP. However, there are a few
> situations where it will screwup. For example, if the client roams to
> a different wireless router, and then tries to renew the DHCP lease,
> it will fail because the lease can only be renewed by the DHCP server
> that originally issued the lease.
>
>>Therefore, if I configure just one of these wirless routers as dhcp, will
>>clients be able to get connected even if they are connecting to router in
>>their area which is NOT the network dhcp server?
>
> No clue or guess. Kindly disclose the maker and model numbers along
> with the topology (wiring and interconnections). There are several
> ways to configure such a system. Some will work, some will not.
>
> Why don't you have the "main office router" act as the DCHP server?
> That way, you don't need wireless routers and can use wireless access
> points.
>
>>Will they be able to discover an IP address from the server even though
>>they
>>do are not able to reach it ?
>
> No clue. I need to know the hardware and topology.
>
>>So far, I am having intermittent success with this.
>
> Intermittent success is not very successful. My guess(tm) is that
> your clients are roaming to different wireless routers, which is
> causing problems.
>
>>Why can I not set up each router as dhcp servers but using different
>>non-conflicting IP ranges ?
>
> You can. You just can't roam between access points with such an
> arrangement. If you have all your wireless routers set for the same
> SSID, you won't even know if a client has roamed until it tries to
> renew the DHCP lease, and fails.
>
> In case you missed it.... Make, model, harware version, topology, etc.
>
>
>
> --
> Jeff Liebermann jeffl@cruzio.com
> 150 Felker St #D http://www.LearnByDestroying.com
> Santa Cruz CA 95060 http://802.11junk.com
> Skype: JeffLiebermann AE6KS 831-336-2558



--
Posted via a free Usenet account from http://www.teranews.com

[Jeff Liebermann]

"-keevill-" <keevill@gmail.com> hath wroth:

>They are wireless routers SMC2904wbra2

Google does not find that device number. Could you verify that this
is the correct number and possibly supply a URL?

>All have different SSID's

Good. Then they won't roam.

>They are wired with RJ45 cables running from an initial Router ( same make
>and model ) which itself is connected to the ADSL Internet connection.
>I think it's fair to say very simple topography.

The main router obviously has the WAN port connected to a broadband
modem of some sorts. The LAN ports probably go to the 4 other boxes.
Are you connecting these 4 cables to the WAN port on the 4 routers, or
to the LAN port? It makes a huge difference.

>There should be no need for PC's to roam between routers but of course some
>will be able to contact 2 routers.

With different SSID's, a user can select the wireless router of
choice.

>Hope that's enough for some ideas of best way to manage things.

Well, I think you should do it like this:

1. Setup the IP address of the 4 satellite routers on different
sequential IP's. For example:
192.168.1.1 main router
192.168.1.2 satellite router #1
(...)
192.168.1.5 satellite router #5
Each satellite router (access point) must be on a different IP address
in order to properly manage and monitor them.

2. Disable the DHCP servers in the 4 satellite routers. The only
DHCP server running will be in the main router.

3. Setup the DHCP server in the main router for a range of:
192.168.1.100 thru 192.168.1.149
50 IP address should be enough.

4. Run the CAT5 cables from the 4 LAN ports on the main router to one
of the *LAN* (not WAN) ports of the 4 satellite routers. This
effectively converts them into wireless access points. The router
section is disabled and not used. No cable goes ot the WAN ports.

5. Setup the 4 satellite access points on different RF channels (1,
6, and 11) but with the same SSID. Since they have the same default
gateway and the same DHCP server no matter which access point a user
connects, the DHCP renewal process will work.

--
Jeff Liebermann jeffl@cruzio.com
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558

[Bill Kearney]

> All have different SSID's

Why?

If all your devices (laptops, pcs, etc) are connecting to the same subnet
then it's often best to use a single DHCP server. If they're all on the
same network then you HAVE TO do this. If they're on different subnets (and
there are plenty of good reasons for/against this) then you'd want to look
into DHCP forwarding. The wifi devices are configured as routers. Each
expecting to have it's own subnet behind it. As in, the main network is
192.168.5.0 and the wifi networks are on, say 192.168.12, .54, .120 and
..188. They could be on any numbering, nor does it matter their sequence.
You'd then configure them to DHCP forward any requests to a central DHCP
server on the main 192.168.5.0 network. On that DHCP server you'd setup
ranges for them (.12, .54, .120, .188 or whatever). This way you get a
central place to administer all DHCP settings.

Alternatively you could configure the wifi units as access points. Here
they act as passive connectors, any hosts connecting to them are granted
DHCP from whatever DHCP server is active on the wired network. The main
network tracks which device is on which wifi access point based on ARP
tables (stuff you normally never see).

There are a number of different scenarios that might be applicable here.
You'd have to better describe what your network and users need before
deciding what sort of scheme is appropriate. This ends up being more of a
generic networking question than wireless.

-Bill Kearney

[-keevill-]

"Bill Kearney" <wkearney99@hotmail.com> wrote in message
news:QcednZqqWsiNH1DanZ2dnUVZ_uGknZ2d@speakeasy.net...
>> All have different SSID's
>
> Why?
>
> If all your devices (laptops, pcs, etc) are connecting to the same subnet
> then it's often best to use a single DHCP server. If they're all on the
> same network then you HAVE TO do this. If they're on different subnets
> (and there are plenty of good reasons for/against this) then you'd want to
> look into DHCP forwarding. The wifi devices are configured as routers.
> Each expecting to have it's own subnet behind it. As in, the main network
> is 192.168.5.0 and the wifi networks are on, say 192.168.12, .54, .120 and
> .188. They could be on any numbering, nor does it matter their sequence.
> You'd then configure them to DHCP forward any requests to a central DHCP
> server on the main 192.168.5.0 network. On that DHCP server you'd setup
> ranges for them (.12, .54, .120, .188 or whatever). This way you get a
> central place to administer all DHCP settings.
>
> Alternatively you could configure the wifi units as access points. Here
> they act as passive connectors, any hosts connecting to them are granted
> DHCP from whatever DHCP server is active on the wired network. The main
> network tracks which device is on which wifi access point based on ARP
> tables (stuff you normally never see).
>
> There are a number of different scenarios that might be applicable here.
> You'd have to better describe what your network and users need before
> deciding what sort of scheme is appropriate. This ends up being more of a
> generic networking question than wireless.
>
> -Bill Kearney

They are all on the same subnet
192.168.0.xx
They all connect to the same network
"mynetwork"
Each wireless router is acting as access points - since they are each
connected via LAN cabling from the ADSL modem / router into on of their LAN
sockets ( not WAN ).
So, I am sure I read it correctly that I must turn off the dhcp on each of
the access points and turn it on ONLY on the ADSL modem/router.
Users connecting to each access point will be able to get an IP address via
this 'central' DHCP server .
Many thanks for help from both posters.
-keevill-



--
Posted via a free Usenet account from http://www.teranews.com

[Bill Kearney]

> They are all on the same subnet 192.168.0.xx

A quick check, you do not have more than 254 devices there do you? If you
did then you'd need to get into different subnet planning. Move to a class
B, the 172.16.x.x range is just for that purpose.

> They all connect to the same network "mynetwork"

I take it by this you mean the SSID are all the same?

> Each wireless router is acting as access points - since they are each
> connected via LAN cabling from the ADSL modem / router into on of their
> LAN sockets ( not WAN ).
> So, I am sure I read it correctly that I must turn off the dhcp on each of
> the access points and turn it on ONLY on the ADSL modem/router.
> Users connecting to each access point will be able to get an IP address
> via this 'central' DHCP server .

Yes, that's what should happen.

[-keevill-]

"Bill Kearney" <wkearney99@hotmail.com> wrote in message
news:voWdnaA9RfFvi1PanZ2dnUVZ_vGinZ2d@speakeasy.net...
>> They are all on the same subnet 192.168.0.xx
>
> A quick check, you do not have more than 254 devices there do you? If you
> did then you'd need to get into different subnet planning. Move to a
> class B, the 172.16.x.x range is just for that purpose.

Only about 40 devices max !

>> They all connect to the same network "mynetwork"

No this means they all connect to the same Domain / Workgroup

> I take it by this you mean the SSID are all the same?


No they are all slightly different .. 'router_1' ' router_2" etc etc
I am toying with the idea put up by another post where I use the same SSID
but different channels...



>
>> Each wireless router is acting as access points - since they are each
>> connected via LAN cabling from the ADSL modem / router into on of their
>> LAN sockets ( not WAN ).
>> So, I am sure I read it correctly that I must turn off the dhcp on each
>> of the access points and turn it on ONLY on the ADSL modem/router.
>> Users connecting to each access point will be able to get an IP address
>> via this 'central' DHCP server .
>
> Yes, that's what should happen.



--
Posted via a free Usenet account from http://www.teranews.com

[Bill Kearney]

> Only about 40 devices max !

Ok, just make sure your DHCP settings allow for that many hosts. Some have
a smallish range setup by default.

Also consider that low-end Small-Office/Home-Office (SoHo) gear does not
handle a lot of simultaneous traffic very well. They're targeted toward the
small network with under a dozen devices, max. The reason is the firewall
on them doesn' t have enough memory or CPU to keep too many sessions running
at the same time.

Each time you open a browser and surf to a site you're opening up, usually,
around 8 sessions (some more, some less). Multiply that across multiple
hosts and you run into trouble. One way to alleviate this is to run a proxy
server internally. This funnels the computers through a more controlled
number of sessions. There's a free one called Squid that's worth
considering (available on linux, windows, etc). You may want to keep this
in mind should network traffic get out of hand (which it inevitably will).

-Bill Kearney

>>> They all connect to the same network "mynetwork"
>
> No this means they all connect to the same Domain / Workgroup
>
>> I take it by this you mean the SSID are all the same?
>
>
> No they are all slightly different .. 'router_1' ' router_2" etc etc
> I am toying with the idea put up by another post where I use the same SSID
> but different channels...
>
>
>
>>
>>> Each wireless router is acting as access points - since they are each
>>> connected via LAN cabling from the ADSL modem / router into on of their
>>> LAN sockets ( not WAN ).
>>> So, I am sure I read it correctly that I must turn off the dhcp on each
>>> of the access points and turn it on ONLY on the ADSL modem/router.
>>> Users connecting to each access point will be able to get an IP address
>>> via this 'central' DHCP server .
>>
>> Yes, that's what should happen.
>
>
>
> --
> Posted via a free Usenet account from http://www.teranews.com
>