DHCP superscpes

My current network consists of multiple VLANS connected via the same physical
media. I want to setup a DHCP superscope on our DHCP4 server to handle
dynamic IP address allocation for each subnet.
Our DHCP server currently resides in VLAN 1 and has a VLAN 1 subnet address.
How does the DHCP server determine which pool to assign the appropiate
subnet address to the lease request, originating from different VLANS,
understanding that requesting clients submit an all 1's broadcast to initiate
the DHCP lease process?

"=?Utf-8?B?S01OUg==?=" <(E-Mail Removed)> wrote in
news:9C8737D4-4983-471D-A8A1-(E-Mail Removed):

> My current network consists of multiple VLANS connected via the same
> physical media. I want to setup a DHCP superscope on our DHCP4 server
> to handle dynamic IP address allocation for each subnet.
> Our DHCP server currently resides in VLAN 1 and has a VLAN 1 subnet
> address. How does the DHCP server determine which pool to assign the
> appropiate subnet address to the lease request, originating from
> different VLANS, understanding that requesting clients submit an all
> 1's broadcast to initiate the DHCP lease process?
>

The DHCP server assigns IP addresses based on the network address of the
first router through which the request passes. So let's say you have
three VLANS -- on the VLAN-aware router you configure the router as the
default gateway with a different IP addr for each VLAN. Then you
configure scopes on the DHCP server to correspond to the IP address
range you intend to use for each VLAN.

So if VLAN 1 is range 192.168.1.0-254, you configure the router IP for
VLAN 1 as (for example) 192.168.1.1. Then you create a scope on the
DHCP server using this address range, and you configure the router (and
all other routers between the client and the DHCP server) to forward
DHCP messages. When a client on VLAN 1 sends a DHCP discover, the
message contains the statically configured IP address of the router
(which is the client's default gateway) -- which is 192.168.1.1. The
DHCP server therefore leases an IP address from this range to the
client.

HTH --

FA

No superscopes! That is not what they are for,...in fact I have never really
seen their use explained clearly enough to make any real sense,..or at least
good enough to prove they are ever really unavoidably needed. There are
always better ways which end up preventing them from being needed.

Use a separate distinct scope for each subnet (VLAN). Leave the DHCP in a
single VLAN. Configure the Router(s) to forward DHCP Queries. The routers
will include the required information so the DHCP Server knows where it came
from and from what scope to pull from.

There is no functional difference between VLANs and physical LANs,...it
still works the same way. VLANs share the same cable physically but *not*
"logically", and it is only the "logical" realm that matters with VLANs. So
you do *not* have the same situation as running multiple physical LANs over
the same physical cable,....which is one of the described purposes of
Superscopes.

Ours here is a hybrid of VLAN and physical LAN,...everything works fine and
I am careful to never over-complicate things.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com



"KMNR" <(E-Mail Removed)> wrote in message
news:9C8737D4-4983-471D-A8A1-(E-Mail Removed)...
> My current network consists of multiple VLANS connected via the same
physical
> media. I want to setup a DHCP superscope on our DHCP4 server to handle
> dynamic IP address allocation for each subnet.
> Our DHCP server currently resides in VLAN 1 and has a VLAN 1 subnet
address.
> How does the DHCP server determine which pool to assign the appropiate
> subnet address to the lease request, originating from different VLANS,
> understanding that requesting clients submit an all 1's broadcast to
initiate
> the DHCP lease process?

Hi Phillip.

Superscopes?? My understanding is that they are only good for multinetting
where you have more than one logical network on the same physical network??
Such a case would be that you have filled up a class C network and you
decide for whatever reason that the solution for more IP's is to add another
class C network [192.168.1.1 and 192.168.1.2 for example] and to accommodate
DHCP you use supercopes. Then you have the problem of computers with
different network addresses on the same physical segment finding each other
which can be done by configuring the default gateway or first router in the
path to the default gateway to send the traffic back to the originating
network side router interface where arp takes over. That's pretty much how I
understand it which may be mostly wrong. --- Steve


"Phillip Windell" <@.> wrote in message
news:(E-Mail Removed)...
> No superscopes! That is not what they are for,...in fact I have never
> really
> seen their use explained clearly enough to make any real sense,..or at
> least
> good enough to prove they are ever really unavoidably needed. There are
> always better ways which end up preventing them from being needed.
>
>> --
>
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
>
>
> "KMNR" <(E-Mail Removed)> wrote in message
> news:9C8737D4-4983-471D-A8A1-(E-Mail Removed)...
>> My current network consists of multiple VLANS connected via the same
> physical
>> media. I want to setup a DHCP superscope on our DHCP4 server to handle
>> dynamic IP address allocation for each subnet.
>> Our DHCP server currently resides in VLAN 1 and has a VLAN 1 subnet
> address.
>> How does the DHCP server determine which pool to assign the appropiate
>> subnet address to the lease request, originating from different VLANS,
>> understanding that requesting clients submit an all 1's broadcast to
> initiate
>> the DHCP lease process?
>
>

"Steven L Umbach" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hi Phillip.
>
> Superscopes?? My understanding is that they are only good for multinetting
> where you have more than one logical network on the same physical
network??

I think we are saying the same thing. In the diagram I saw it had two
distinct networks (nothing "logical", no VLANs) that were simply running on
the same physical network (the wiring). They used it to illustrate the need
for Superscopes. But it wasn't really clear to me "why".

VLANs aren't the same situation because traffic is separated by "frame
tagging", so even though it is on the same physical wire,..it really isn't
on the same physical wire,...if that makes any sense.. :-) The "frame
tagging" creates the same effect as having two different and completely
isolated physical segments

One other thing I read claimed Superscopes are used to take multiple scopes
and make them behave as a single scope. But when I read that I
thought,...What's the point??,..this is so easily over come by supernetting
by simply borrowing bits from the network side of the mask that the whole
thing was silly. So to this day I still haven't seen a clear example of
when a superscope would be absolutely needed with no other way around it. In
every case I've seen it is so simple and so easy to avoid them that it makes
them kind of pointless.

But maybe there is someone that can clear it up for me.

--

Phillip Windell [MCP, MVP, CCNA]
www.wandtv.com