Subnetting newbie question... is this possible?

I have a Netgear router in my house which I've been using for its typical
purpose: sharing my cable modem. There are about 5-6 hosts attached to this
router at any given time and it is acting as DHCP server, dishing out
192.168.0.x addresses

Recently I set up a Windows 2003 Server for testing/educational purposes. I
just want to attach a client or two to it and play with RIS, DHCP and DNS
among other things.

What I'd like to do is isolate it completely from the other hosts.... one
client, one server on one subnet.

Went into the router and reserved 192.168.0.2 (for the server) and
192.168.0.10 (for the client).

Then I went into the NIC settings for each and hard-coded the IP address
IP: 192.168.0.2
Subnet Mask: 255.255.255.240
Default Gateway: 192.168.0.1 (the Netgear router)
Preferred DNS: 192.168.0.1 (the Netgear router)

Did the same on the 192.168.0.10 system

The two systems should not be able to communicate with any other system but
the other one on the subnet, correct?

Also, what hapeens if I turn DHCP on for my server and the router is also
acting as DHCP? The client grabs whatever IP addresss it gets first?

Big time newbie questions, I know. Be kind.

JM

"Joe Murphy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Then I went into the NIC settings for each and hard-coded the IP address
> IP: 192.168.0.2
> Subnet Mask: 255.255.255.240
> Default Gateway: 192.168.0.1 (the Netgear router)
> Preferred DNS: 192.168.0.1 (the Netgear router)

The "240" mask gives these subnets.
*.0 -- *.15
*.16 -- *.31
etc.

You never went higher than 10, so everything is still in the same subnet
(first one).

> The two systems should not be able to communicate with any other system
but
> the other one on the subnet, correct?

Yes, but only if this "Lab" Sever and Host use an IP above 16. Like:

192.168.0.17 [255.255.255.240]
192.168.0.18 [255.255.255.240]

Everything everywhere, including the Netgear Device, has to use the same
Mask on the LAN side. The Netgear box will not be able to see the two Lab
machines, nor will the two Lab machines be able the go through it to the
Internet. That would require a static route on the Netgear box and it would
require a Router (which you don't have,..the Netgear box is not a router
inspite of what the marketeers call it).

> Also, what hapeens if I turn DHCP on for my server and the router is also
> acting as DHCP?

Nothing.

> The client grabs whatever IP addresss it gets first?

DHCP does not cross subnets.
The DHCP Config (Scope) must also have the mask changed to *.240

Thanks for your reply. A couple of novice observations, if you don't
mind....

> *.0 -- *.15
> *.16 -- *.31

I thought the .240 mask gave me just 15 hosts?

> Everything everywhere, including the Netgear Device, has to use the same
> Mask on the LAN side. The Netgear box will not be able to see the two Lab
> machines, nor will the two Lab machines be able the go through it to the
> Internet. That would require a static route on the Netgear box and it
> would
> require a Router (which you don't have,..the Netgear box is not a router
> inspite of what the marketeers call it).

Understood, but how was I able to continue browsing with the server and
client machines through the Netgear box and out to the Internet?

When I took out the preferred DNS of 192.168.0.1 I was unable to browse
Internet. Put it back in and, presto, I could browse again.

--

_______________________________
http://boston.craigslist.org/about/b.../62974620.html
"Phillip Windell" <@.> wrote in message
news:%(E-Mail Removed)...
> "Joe Murphy" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Then I went into the NIC settings for each and hard-coded the IP address
>> IP: 192.168.0.2
>> Subnet Mask: 255.255.255.240
>> Default Gateway: 192.168.0.1 (the Netgear router)
>> Preferred DNS: 192.168.0.1 (the Netgear router)
>
> The "240" mask gives these subnets.
> *.0 -- *.15
> *.16 -- *.31
> etc.
>
> You never went higher than 10, so everything is still in the same subnet
> (first one).
>
>> The two systems should not be able to communicate with any other system
> but
>> the other one on the subnet, correct?
>
> Yes, but only if this "Lab" Sever and Host use an IP above 16. Like:
>
> 192.168.0.17 [255.255.255.240]
> 192.168.0.18 [255.255.255.240]
>

>
>> Also, what hapeens if I turn DHCP on for my server and the router is also
>> acting as DHCP?
>
> Nothing.
>
>> The client grabs whatever IP addresss it gets first?
>
> DHCP does not cross subnets.
> The DHCP Config (Scope) must also have the mask changed to *.240
>
>

here's the breakdown of ip addressing for the .240 block in question- dots
mean i'm too lazy to count each instance of a usable host-

..0 subnet id
..1 router ("default gateway")
..2 usable host
..3 usable host
..
..
..14 usable host
..15 broadcast id
..16 subnet id
..17 router ("default gateway")
..18 usable host
..
..30 usable host
..31 broadcastid


in a /28 network, you really only get 13 usable hosts out of 16 total
addresses in the network- 2 for network boundary and 1 for the router in the
network.


Dan Farrell
Applied Innovations Corp.

"Joe Murphy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Thanks for your reply. A couple of novice observations, if you don't
> mind....
>
>> *.0 -- *.15
>> *.16 -- *.31
>
> I thought the .240 mask gave me just 15 hosts?
>
>> Everything everywhere, including the Netgear Device, has to use the same
>> Mask on the LAN side. The Netgear box will not be able to see the two Lab
>> machines, nor will the two Lab machines be able the go through it to the
>> Internet. That would require a static route on the Netgear box and it
>> would
>> require a Router (which you don't have,..the Netgear box is not a router
>> inspite of what the marketeers call it).
>
> Understood, but how was I able to continue browsing with the server and
> client machines through the Netgear box and out to the Internet?
>
> When I took out the preferred DNS of 192.168.0.1 I was unable to browse
> Internet. Put it back in and, presto, I could browse again.
>
> --
>
> _______________________________
> http://boston.craigslist.org/about/b.../62974620.html
> "Phillip Windell" <@.> wrote in message
> news:%(E-Mail Removed)...
>> "Joe Murphy" <(E-Mail Removed)> wrote in message
>> news:(E-Mail Removed)...
>>> Then I went into the NIC settings for each and hard-coded the IP address
>>> IP: 192.168.0.2
>>> Subnet Mask: 255.255.255.240
>>> Default Gateway: 192.168.0.1 (the Netgear router)
>>> Preferred DNS: 192.168.0.1 (the Netgear router)
>>
>> The "240" mask gives these subnets.
>> *.0 -- *.15
>> *.16 -- *.31
>> etc.
>>
>> You never went higher than 10, so everything is still in the same subnet
>> (first one).
>>
>>> The two systems should not be able to communicate with any other system
>> but
>>> the other one on the subnet, correct?
>>
>> Yes, but only if this "Lab" Sever and Host use an IP above 16. Like:
>>
>> 192.168.0.17 [255.255.255.240]
>> 192.168.0.18 [255.255.255.240]
>>
>
>>
>>> Also, what hapeens if I turn DHCP on for my server and the router is
>>> also
>>> acting as DHCP?
>>
>> Nothing.
>>
>>> The client grabs whatever IP addresss it gets first?
>>
>> DHCP does not cross subnets.
>> The DHCP Config (Scope) must also have the mask changed to *.240
>>
>>
>
>

Thanks Dan, but this is confusing still.

I have a /28 network, like you said, and that should give me 16 hosts.

From your notation I see the following addresses available:

..2 .3 .4 .5 .6 .7 .8 .9 .10 .11 .12 .13 .14
..18. 19. 20. 21. 22. 23 .24 .25 .26 .27 .28. 29 .30

That's more like 26 hosts, no?


"Dan Farrell" <(E-Mail Removed)> wrote in message
news:%23M$(E-Mail Removed)...
> here's the breakdown of ip addressing for the .240 block in question- dots
> mean i'm too lazy to count each instance of a usable host-
>
> .0 subnet id
> .1 router ("default gateway")
> .2 usable host
> .3 usable host
> .
> .
> .14 usable host
> .15 broadcast id
> .16 subnet id
> .17 router ("default gateway")
> .18 usable host
> .
> .30 usable host
> .31 broadcastid
>
>
> in a /28 network, you really only get 13 usable hosts out of 16 total
> addresses in the network- 2 for network boundary and 1 for the router in
> the network.
>
>
> Dan Farrell
> Applied Innovations Corp.
>
> "Joe Murphy" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Thanks for your reply. A couple of novice observations, if you don't
>> mind....
>>
>>> *.0 -- *.15
>>> *.16 -- *.31
>>
>> I thought the .240 mask gave me just 15 hosts?
>>
>>> Everything everywhere, including the Netgear Device, has to use the same
>>> Mask on the LAN side. The Netgear box will not be able to see the two
>>> Lab
>>> machines, nor will the two Lab machines be able the go through it to the
>>> Internet. That would require a static route on the Netgear box and it
>>> would
>>> require a Router (which you don't have,..the Netgear box is not a router
>>> inspite of what the marketeers call it).
>>
>> Understood, but how was I able to continue browsing with the server and
>> client machines through the Netgear box and out to the Internet?
>>
>> When I took out the preferred DNS of 192.168.0.1 I was unable to browse
>> Internet. Put it back in and, presto, I could browse again.
>>
>> --
>>
>> _______________________________
>> http://boston.craigslist.org/about/b.../62974620.html
>> "Phillip Windell" <@.> wrote in message
>> news:%(E-Mail Removed)...
>>> "Joe Murphy" <(E-Mail Removed)> wrote in message
>>> news:(E-Mail Removed)...
>>>> Then I went into the NIC settings for each and hard-coded the IP
>>>> address
>>>> IP: 192.168.0.2
>>>> Subnet Mask: 255.255.255.240
>>>> Default Gateway: 192.168.0.1 (the Netgear router)
>>>> Preferred DNS: 192.168.0.1 (the Netgear router)
>>>
>>> The "240" mask gives these subnets.
>>> *.0 -- *.15
>>> *.16 -- *.31
>>> etc.
>>>
>>> You never went higher than 10, so everything is still in the same subnet
>>> (first one).
>>>
>>>> The two systems should not be able to communicate with any other system
>>> but
>>>> the other one on the subnet, correct?
>>>
>>> Yes, but only if this "Lab" Sever and Host use an IP above 16. Like:
>>>
>>> 192.168.0.17 [255.255.255.240]
>>> 192.168.0.18 [255.255.255.240]
>>>
>>
>>>
>>>> Also, what hapeens if I turn DHCP on for my server and the router is
>>>> also
>>>> acting as DHCP?
>>>
>>> Nothing.
>>>
>>>> The client grabs whatever IP addresss it gets first?
>>>
>>> DHCP does not cross subnets.
>>> The DHCP Config (Scope) must also have the mask changed to *.240
>>>
>>>
>>
>>
>
>

"Joe Murphy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Thanks for your reply. A couple of novice observations, if you don't
> mind....
>
> > *.0 -- *.15
> > *.16 -- *.31
>
> I thought the .240 mask gave me just 15 hosts?

256 is the maximum addresses provided by a Byte
( 0 thru 255 is 256 addesses because "0" also counts)

Subtract the Mask number from it to get number of addresses.
256 - 240 = 16 addresses in the subnet
You lose 2 addresses for the ID and Broadcast Address (first and last), so:
16 - 2 = 14 Hosts



192.168.0.0 = ID of first subnet
192.168.0.15 = Broadcast of first subnet
192.168.0.1 -- 192.168.0.14 = Range of usable hosts

192.168.0.16 = ID of second subnet
192.168.0.31 = Broadcast of second subnet
192.168.0.17 -- 192.168.0.30 = Range of usable hosts

Rinse & Repeat the pattern for the rest.

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

"Joe Murphy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Thanks Dan, but this is confusing still.
>
> I have a /28 network, like you said, and that should give me 16 hosts.
>
> From your notation I see the following addresses available:
>
> .2 .3 .4 .5 .6 .7 .8 .9 .10 .11 .12 .13 .14
> .18. 19. 20. 21. 22. 23 .24 .25 .26 .27 .28. 29 .30
>
> That's more like 26 hosts, no?

No. You missunderstand what he wrote. Look at my other post, it shows the
same thing but in a different way. I say 14 instead of 13 hosts becasue I
consider the router to be another host,...just want to make sure you didn't
trip over that either.

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

Yeah what is was illustrating was two /28's in a row, starting at the
beginning of a class C.

In your response you broke down your answer of the addresses into two lines-
each one of those lines are a /28.

a /28 contains a total of 16 addresses, but like all other networks, you
always have a 3 address overhead minimum-

-subnetid
-router
-broadcastid

You could remove the router, but then you would have a closed network
un-connected to any other networks.
So in a 'x' network you get 'y' usable hosts-

x - y
/30 - 1
/29 - 5
/28 - 13
/27 - 29
/26 - 61
/25 - 125
/24 - 253

Now as soon as that rule crystallizes in your mind (took me a awhile when I
first learned this, too) here's one to uncrystallize it-

The subnetid address of a network must be divisible by the total number of
hosts in that subnet(not the total number of usable hosts).
This rule will make sure that subnetted networks will begin at the correct
address- subnetted networks can't simply be placed anywhere within a Class
C.

Example-

you want a /28 (.240 subnet) but you're not sure where you can 'start' the
network within a Class C. You consider .15 , but 15/16 = non-whole number,
so that won't work. but .16 would work, 16/16 = 1. other valid subnet
boundaries for a /28, therefore, could be-

..0
..32
..48
..64.
..80
..96

and so on. Make sense? I can supply other examples if you desire...

danno




"Phillip Windell" <@.> wrote in message
news:(E-Mail Removed)...
>
> "Joe Murphy" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed)...
>> Thanks Dan, but this is confusing still.
>>
>> I have a /28 network, like you said, and that should give me 16 hosts.
>>
>> From your notation I see the following addresses available:
>>
>> .2 .3 .4 .5 .6 .7 .8 .9 .10 .11 .12 .13 .14
>> .18. 19. 20. 21. 22. 23 .24 .25 .26 .27 .28. 29 .30
>>
>> That's more like 26 hosts, no?
>
> No. You missunderstand what he wrote. Look at my other post, it shows the
> same thing but in a different way. I say 14 instead of 13 hosts becasue I
> consider the router to be another host,...just want to make sure you
> didn't
> trip over that either.
>
> --
> Phillip Windell [MCP, MVP, CCNA]
> www.wandtv.com
>
>

"Joe Murphy" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Thanks Dan, but this is confusing still.
>
> I have a /28 network, like you said, and that should give me 16 hosts.
>
> From your notation I see the following addresses available:
>
> .2 .3 .4 .5 .6 .7 .8 .9 .10 .11 .12 .13 .14
> .18. 19. 20. 21. 22. 23 .24 .25 .26 .27 .28. 29 .30
>
> That's more like 26 hosts, no?

Looks like an oops
Using the link below someone was kind of nice to post a nice breakout.
In your above example it should be .0 to .15 for the first line with .0
being the subnet and .15 being the broadcast address, giving you 14 host
addresses, .1 through .14
The second line should be .16 to .31, .16 being the subnet, .31 being the
broadcast and .17 through .30 being hosts
https://www.ncsd.k12.ca.us/sysmgr/subnet-table
>
>
> "Dan Farrell" <(E-Mail Removed)> wrote in message
> news:%23M$(E-Mail Removed)...
> > here's the breakdown of ip addressing for the .240 block in question-
dots
> > mean i'm too lazy to count each instance of a usable host-
> >
> > .0 subnet id
> > .1 router ("default gateway")
> > .2 usable host
> > .3 usable host
> > .
> > .
> > .14 usable host
> > .15 broadcast id
> > .16 subnet id
> > .17 router ("default gateway")
> > .18 usable host
> > .
> > .30 usable host
> > .31 broadcastid
> >
> >
> > in a /28 network, you really only get 13 usable hosts out of 16 total
> > addresses in the network- 2 for network boundary and 1 for the router in
> > the network.
> >
> >
> > Dan Farrell
> > Applied Innovations Corp.
> >
> > "Joe Murphy" <(E-Mail Removed)> wrote in message
> > news:(E-Mail Removed)...
> >> Thanks for your reply. A couple of novice observations, if you don't
> >> mind....
> >>
> >>> *.0 -- *.15
> >>> *.16 -- *.31
> >>
> >> I thought the .240 mask gave me just 15 hosts?
> >>
> >>> Everything everywhere, including the Netgear Device, has to use the
same
> >>> Mask on the LAN side. The Netgear box will not be able to see the two
> >>> Lab
> >>> machines, nor will the two Lab machines be able the go through it to
the
> >>> Internet. That would require a static route on the Netgear box and it
> >>> would
> >>> require a Router (which you don't have,..the Netgear box is not a
router
> >>> inspite of what the marketeers call it).
> >>
> >> Understood, but how was I able to continue browsing with the server and
> >> client machines through the Netgear box and out to the Internet?
> >>
> >> When I took out the preferred DNS of 192.168.0.1 I was unable to browse
> >> Internet. Put it back in and, presto, I could browse again.
> >>
> >> --
> >>
> >> _______________________________
> >> http://boston.craigslist.org/about/b.../62974620.html
> >> "Phillip Windell" <@.> wrote in message
> >> news:%(E-Mail Removed)...
> >>> "Joe Murphy" <(E-Mail Removed)> wrote in message
> >>> news:(E-Mail Removed)...
> >>>> Then I went into the NIC settings for each and hard-coded the IP
> >>>> address
> >>>> IP: 192.168.0.2
> >>>> Subnet Mask: 255.255.255.240
> >>>> Default Gateway: 192.168.0.1 (the Netgear router)
> >>>> Preferred DNS: 192.168.0.1 (the Netgear router)
> >>>
> >>> The "240" mask gives these subnets.
> >>> *.0 -- *.15
> >>> *.16 -- *.31
> >>> etc.
> >>>
> >>> You never went higher than 10, so everything is still in the same
subnet
> >>> (first one).
> >>>
> >>>> The two systems should not be able to communicate with any other
system
> >>> but
> >>>> the other one on the subnet, correct?
> >>>
> >>> Yes, but only if this "Lab" Sever and Host use an IP above 16. Like:
> >>>
> >>> 192.168.0.17 [255.255.255.240]
> >>> 192.168.0.18 [255.255.255.240]
> >>>
> >>
> >>>
> >>>> Also, what hapeens if I turn DHCP on for my server and the router is
> >>>> also
> >>>> acting as DHCP?
> >>>
> >>> Nothing.
> >>>
> >>>> The client grabs whatever IP addresss it gets first?
> >>>
> >>> DHCP does not cross subnets.
> >>> The DHCP Config (Scope) must also have the mask changed to *.240
> >>>
> >>>
> >>
> >>
> >
> >
>
>

"Dan Farrell" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> You could remove the router, but then you would have a closed network
> un-connected to any other networks.

No, I don't imply removing the router,...I just consider it another "host"
while the ID and the B-Cast definately are not hosts.

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