Running out of IP addresses

microsoft.public.windows.server.networking

28 Nov 2007 8:43 PM

Maurice Bishop

I am running out of useable IP addresses on my subnet.

I have a network of 5 servers running Windows 2003 server on the same
domain, one of which runs DHCP for the whole network on one subnet. There
are approximately 110 client computers. In total, with workstations,
servers, routers, print servers, multi function devices etc, there are about
220 IP addresses used on the LAN.

I have a subnet of 255.255.255.0 with DHCP scope 192.168.1.10 thru
192.168.1.130

I cannot extend the present scope to include IP addresses above 130 as I
have static address assignments above 130 that cannot be moved without a
considerable amount of hassle.

Can I change the subnet to 255.255.0.0 and start to use a second scope of
192.168.2.10 thru 192.168.2.254 ?

Will this work seemlessly? Is there any other way of getting a useable
private IP address range?

TX in advance

Maurice

28 Nov 2007 9:50 PM

Phillip Windell

First. Scopes should always include the entire address range (*.1-*.254)
then control it with Exclusions.

The subnet has 254 possible addresses,...there is no way you would run out.
You still have 35 left over even if every single device was powered up and
running all at the same time.

> I cannot extend the present scope to include IP addresses above 130 as I
> have static address assignments above 130 that cannot be moved without a
> considerable amount of hassle.

Go around them. If they are sequential them mark them out with an Exclusion.
You probably have a chunk of addresses above them that aren't used. They
can be added to the dynamic group of addresses by simply not including them
in an Exclusion. In other words when you exclude 130 an up you don't have
to go all the way to 254. I actually have two distinct Exclusion ranges in
mine.

> Can I change the subnet to 255.255.0.0 and start to use a second scope of
> 192.168.2.10 thru 192.168.2.254 ?

No.

1. It would go in the same scope,..not a new scope. But since you cannot
edit a Scope in that way you would have to delete the existing one and
create and entirely new one for the whole thing. That could be a lot of
work if their are a lot of Scope Options or Reservations,...and there would
be no DHCP available during the period that this was being performed.

2. Ethernet is not supposed to have subnets bigger than 254 hosts.
Efficiency starts to drop off due to broadcasts at around 250 to 300 hosts
depending on the type of traffic already on the wire.
"But a lot of people are doing it!",...yes and a lot of networks perform
like crap when they are hit with a "real" load and they will blame
everything except the real cause. Some are just lucky because they don't
generate a lot of traffic to start with, so the problem is "unnoticed". Some
have big subnets but simply have not actually filled them up with *too many*
host,...at least not yet.

Faster systems (like gigabit) just aren't noticable to the human perception
that early on because most people would never notice a gigbit network that
actualy only performs like a 100 or 10 mbps system until something "stressed
it" or it was measured with equipment. But if you want a gigabit system to
actually run at gigabit speed,..the same rules apply.

To go more than 254 hosts,...create a whole new subnet and put a LAN Router
between them. You can build it first and get it working with no machines
even on it. Then gradually over time start moving some things over to it as
is becomes convienient. If you create a new 254 host segment then you will
have a 508 host capacity and won't run into trouble with broadcast and will
be able to grow and double in size without any topology changes at all.
Don't forget to install WINS on at least one server and use it. Some things
still require netbios resolution and WINS is required for it to function
across routers.

--
Phillip Windell
www.wandtv.com

The views expressed, are my own and not those of my employer, or Microsoft,
or anyone else associated with me, including my cats.
-----------------------------------------------------

29 Nov 2007 1:57 AM

Maurice Bishop

Terrific.

I understand. Given the growth of the company and the need to properly
manage bandwidth, contention, performance, minimize broadcasts etc., I will:

Out of office hours:

a. Remove the existing DHCP scope having first made a note of existing
reservations.
b. Create a new scope embracing the full subnet 1 thru 254 and assign the
reservations.
c. Stop and restart the DHCP service.

I think it worth planning a second subnet at this stage as I can see the
existing scope running out, even with a 'full range' on the current subnet.
I understand that I will need to introduce a DHCP server on the second
subnet. Rather than introduce a hardware LAN router, could I insert a new
LAN card into one of the existing Windows 2003 servers to service the second
subnet (192.168.2.*) and use the routing features therein?

I understand the need to implement a WINS server on each subnet. Will I need
to make an entry in the WINS local database for all foreign (other subnet)
machines/IP addresses?

TX in advance

Maurice

Show quote

"Phillip Windell" <philwind***@hotmail.com> wrote in message
news:e6F3GjgMIHA.5400@TK2MSFTNGP04.phx.gbl...
> "Maurice Bishop" <no.spam.here.please@not.hereplease.com> wrote in message
> news:13krkn1hts7jdf5@corp.supernews.com...
>>I am running out of useable IP addresses on my subnet.
>>
>> I have a network of 5 servers running Windows 2003 server on the same
>> domain, one of which runs DHCP for the whole network on one subnet. There
>> are approximately 110 client computers. In total, with workstations,
>> servers, routers, print servers, multi function devices etc, there are
>> about 220 IP addresses used on the LAN.
>
> First. Scopes should always include the entire address range (*.1-*.254)
> then control it with Exclusions.
>
> The subnet has 254 possible addresses,...there is no way you would run
> out. You still have 35 left over even if every single device was powered
> up and running all at the same time.
>
>> I cannot extend the present scope to include IP addresses above 130 as I
>> have static address assignments above 130 that cannot be moved without a
>> considerable amount of hassle.
>
> Go around them. If they are sequential them mark them out with an
> Exclusion. You probably have a chunk of addresses above them that aren't
> used. They can be added to the dynamic group of addresses by simply not
> including them in an Exclusion. In other words when you exclude 130 an up
> you don't have to go all the way to 254. I actually have two distinct
> Exclusion ranges in mine.
>
>> Can I change the subnet to 255.255.0.0 and start to use a second scope of
>> 192.168.2.10 thru 192.168.2.254 ?
>
> No.
>
> 1. It would go in the same scope,..not a new scope. But since you cannot
> edit a Scope in that way you would have to delete the existing one and
> create and entirely new one for the whole thing. That could be a lot of
> work if their are a lot of Scope Options or Reservations,...and there
> would be no DHCP available during the period that this was being
> performed.
>
> 2. Ethernet is not supposed to have subnets bigger than 254 hosts.
> Efficiency starts to drop off due to broadcasts at around 250 to 300
> hosts depending on the type of traffic already on the wire.
> "But a lot of people are doing it!",...yes and a lot of networks perform
> like crap when they are hit with a "real" load and they will blame
> everything except the real cause. Some are just lucky because they don't
> generate a lot of traffic to start with, so the problem is "unnoticed".
> Some have big subnets but simply have not actually filled them up with
> *too many* host,...at least not yet.
>
> Faster systems (like gigabit) just aren't noticable to the human
> perception that early on because most people would never notice a gigbit
> network that actualy only performs like a 100 or 10 mbps system until
> something "stressed it" or it was measured with equipment. But if you want
> a gigabit system to actually run at gigabit speed,..the same rules apply.
>
> To go more than 254 hosts,...create a whole new subnet and put a LAN
> Router between them. You can build it first and get it working with no
> machines even on it. Then gradually over time start moving some things
> over to it as is becomes convienient. If you create a new 254 host
> segment then you will have a 508 host capacity and won't run into trouble
> with broadcast and will be able to grow and double in size without any
> topology changes at all. Don't forget to install WINS on at least one
> server and use it. Some things still require netbios resolution and WINS
> is required for it to function across routers.
>
> --
> Phillip Windell
> www.wandtv.com
>
> The views expressed, are my own and not those of my employer, or
> Microsoft,
> or anyone else associated with me, including my cats.
> -----------------------------------------------------
>
>

29 Nov 2007 2:14 AM

Bill Grant

You could do that. In fact it is pretty hard to find a hardware LAN
router these days. You could use VLANs if your switch is capable of that.

Be careful what server you make a router. A router is obviously
multihomed and there are known problems with multihomed DCs and mail servers
(because of the name being associated with more than one IP address).

Show quote

"Maurice Bishop" <no.spam.here.please@not.hereplease.com> wrote in message
news:13ks75dp6kpcu29@corp.supernews.com...
> Terrific.
>
> I understand. Given the growth of the company and the need to properly
> manage bandwidth, contention, performance, minimize broadcasts etc., I
> will:
>
> Out of office hours:
>
> a. Remove the existing DHCP scope having first made a note of existing
> reservations.
> b. Create a new scope embracing the full subnet 1 thru 254 and assign the
> reservations.
> c. Stop and restart the DHCP service.
>
> I think it worth planning a second subnet at this stage as I can see the
> existing scope running out, even with a 'full range' on the current
> subnet. I understand that I will need to introduce a DHCP server on the
> second subnet. Rather than introduce a hardware LAN router, could I insert
> a new LAN card into one of the existing Windows 2003 servers to service
> the second subnet (192.168.2.*) and use the routing features therein?
>
> I understand the need to implement a WINS server on each subnet. Will I
> need to make an entry in the WINS local database for all foreign (other
> subnet) machines/IP addresses?
>
> TX in advance
>
> Maurice
>
>
>
> "Phillip Windell" <philwind***@hotmail.com> wrote in message
> news:e6F3GjgMIHA.5400@TK2MSFTNGP04.phx.gbl...
>> "Maurice Bishop" <no.spam.here.please@not.hereplease.com> wrote in
>> message news:13krkn1hts7jdf5@corp.supernews.com...
>>>I am running out of useable IP addresses on my subnet.
>>>
>>> I have a network of 5 servers running Windows 2003 server on the same
>>> domain, one of which runs DHCP for the whole network on one subnet.
>>> There are approximately 110 client computers. In total, with
>>> workstations, servers, routers, print servers, multi function devices
>>> etc, there are about 220 IP addresses used on the LAN.
>>
>> First. Scopes should always include the entire address range (*.1-*.254)
>> then control it with Exclusions.
>>
>> The subnet has 254 possible addresses,...there is no way you would run
>> out. You still have 35 left over even if every single device was powered
>> up and running all at the same time.
>>
>>> I cannot extend the present scope to include IP addresses above 130 as I
>>> have static address assignments above 130 that cannot be moved without a
>>> considerable amount of hassle.
>>
>> Go around them. If they are sequential them mark them out with an
>> Exclusion. You probably have a chunk of addresses above them that aren't
>> used. They can be added to the dynamic group of addresses by simply not
>> including them in an Exclusion. In other words when you exclude 130 an
>> up you don't have to go all the way to 254. I actually have two distinct
>> Exclusion ranges in mine.
>>
>>> Can I change the subnet to 255.255.0.0 and start to use a second scope
>>> of 192.168.2.10 thru 192.168.2.254 ?
>>
>> No.
>>
>> 1. It would go in the same scope,..not a new scope. But since you cannot
>> edit a Scope in that way you would have to delete the existing one and
>> create and entirely new one for the whole thing. That could be a lot of
>> work if their are a lot of Scope Options or Reservations,...and there
>> would be no DHCP available during the period that this was being
>> performed.
>>
>> 2. Ethernet is not supposed to have subnets bigger than 254 hosts.
>> Efficiency starts to drop off due to broadcasts at around 250 to 300
>> hosts depending on the type of traffic already on the wire.
>> "But a lot of people are doing it!",...yes and a lot of networks perform
>> like crap when they are hit with a "real" load and they will blame
>> everything except the real cause. Some are just lucky because they don't
>> generate a lot of traffic to start with, so the problem is "unnoticed".
>> Some have big subnets but simply have not actually filled them up with
>> *too many* host,...at least not yet.
>>
>> Faster systems (like gigabit) just aren't noticable to the human
>> perception that early on because most people would never notice a gigbit
>> network that actualy only performs like a 100 or 10 mbps system until
>> something "stressed it" or it was measured with equipment. But if you
>> want a gigabit system to actually run at gigabit speed,..the same rules
>> apply.
>>
>> To go more than 254 hosts,...create a whole new subnet and put a LAN
>> Router between them. You can build it first and get it working with no
>> machines even on it. Then gradually over time start moving some things
>> over to it as is becomes convienient. If you create a new 254 host
>> segment then you will have a 508 host capacity and won't run into trouble
>> with broadcast and will be able to grow and double in size without any
>> topology changes at all. Don't forget to install WINS on at least one
>> server and use it. Some things still require netbios resolution and WINS
>> is required for it to function across routers.
>>
>> --
>> Phillip Windell
>> www.wandtv.com
>>
>> The views expressed, are my own and not those of my employer, or
>> Microsoft,
>> or anyone else associated with me, including my cats.
>> -----------------------------------------------------
>>
>>
>
>

29 Nov 2007 3:13 PM

Phillip Windell

"Maurice Bishop" <no.spam.here.please@not.hereplease.com> wrote in message
news:13ks75dp6kpcu29@corp.supernews.com...
> a. Remove the existing DHCP scope having first made a note of existing
> reservations.
> b. Create a new scope embracing the full subnet 1 thru 254 and assign the
> reservations.
> c. Stop and restart the DHCP service.

You don't have to do that for that situation. You can change the current IP
Range of a Scope,...you just can't change the mask (like making the subnet
bigger). Since the Mask still agrees with the IP Range it is fine. Just
extend the IP Range of the Scope to 1 thru 254, adjust any Exclusions as
needed and you're done.

> I think it worth planning a second subnet at this stage as I can see the
> existing scope running out, even with a 'full range' on the current
> subnet. I understand that I will need to introduce a DHCP server on the
> second subnet. Rather than introduce a hardware LAN router, could I insert
> a new LAN card into one of the existing Windows 2003 servers to service
> the second subnet (192.168.2.*) and use the routing features therein?

You could do it with a duel nic RRAS box, *but*, I recommend you buy a LAN
Router. They aren't that expensive. Don't make your LAN infastructure
dependent on a "PC". There are "gobs and gobs" of Layer3 Switches on the
market at good prices. They are a Switch and a LAN Router built into the
same hardware. Don't confuse these with a normal Layer2 Switch.

1. You just VLAN the switch to split up the Ports into two or more groups
(aka Router Interfaces) and then enable the Layer3 Routing features.

2. Configure the DHCP Helper Addresses within the routing functions of the
switch to point to the DHCP Server

3. Add a new Scope (no superscopes!) to the existing DHCP

4. Install WINS on one of the Servers. I typically use the DC/DNS Server

> I understand the need to implement a WINS server on each subnet. Will I
> need to make an entry in the WINS local database for all foreign (other
> subnet) machines/IP addresses?

No. WINS automatically adds machines that are configured to use it. If it
doesn't automatically add itself (like non-Windows machines) then you
probably don't have to worry about those anyway. WINS is really only
concerned with MS based machines where Network Browsing (Network Places,
Network Neighborhood) is present.

28 Nov 2007 10:01 PM

Anthony

Hi Maurice,
This is a bit of a logistical game.
You could just create another VLAN on your switch and addd another
192.168.xxx.xxx 255.255.255.0 range.
Or you could change the mask to 255.255.254.0 and use the range 192.168.0.0
to 192.168.1.255 (or 255.255.252.0 and 192.168.0.0 to 192.168.3.255). You
would have to figure out which one gives you the least work.
A 254 or 252 mask works fine if you are using WINS to cut down on
broadcasts.
Hope that helps,
Anthony, http://www.airdesk.co.uk

Show quote

"Maurice Bishop" <no.spam.here.please@not.hereplease.com> wrote in message
news:13krkn1hts7jdf5@corp.supernews.com...
>I am running out of useable IP addresses on my subnet.
>
> I have a network of 5 servers running Windows 2003 server on the same
> domain, one of which runs DHCP for the whole network on one subnet. There
> are approximately 110 client computers. In total, with workstations,
> servers, routers, print servers, multi function devices etc, there are
> about 220 IP addresses used on the LAN.
>
> I have a subnet of 255.255.255.0 with DHCP scope 192.168.1.10 thru
> 192.168.1.130
>
> I cannot extend the present scope to include IP addresses above 130 as I
> have static address assignments above 130 that cannot be moved without a
> considerable amount of hassle.
>
> Can I change the subnet to 255.255.0.0 and start to use a second scope of
> 192.168.2.10 thru 192.168.2.254 ?
>
> Will this work seemlessly? Is there any other way of getting a useable
> private IP address range?
>
> TX in advance
>
> Maurice
>