Multiple IP addresses

Hi,

Two weeks after moving house, I've finally got ADSL again (last night), it's
been a painfull & slow two weeks and I'm glad to be on this side of it. ;o)
I swapped from using Freeserve and the accompanying DHCP to using a friendly
local ISP where I get as many static IP addresses as I want.

My old Freeserve setup consisted of a Zoom ADSL router/firewall (the "X4" I
think) connected via ethernet to an 8 port hub. The router had the address
192.168.0.1 and the other computers were 192.168.0.2/3/4 etc. This was kind
of okay but the router's firewall is crap and required a reboot (thus new IP
address) whenever I wanted to change the rules, which was quite often as I
like experimenting a lot.

With my new setup I want every machine on my home LAN to have it's own
(class c?) IP address but I don't know much about this sort of thing. I want
to do something like this:

[MYISP] <> [ADSL MODEM] <> [FREESCO BOX] <> {LAN}{WITH}{MANY}{MACHINES}

The ADSL modem will be my existing Zoom router with forwarding ALL ports
(DMZ feature on the Zoom) to the Freesco machine (I have a cobalt qube but
no PSU, gutted). The way I thought it would work (pure guess work) is:
The router/modem would have the IP (obviously made up here) 212.99.99.1
which would be the gateway for eth0 on the freesco box, eth1 would be
connected to the hub. All the machines LAN side would be assigned
212.99.99.x addresses and use the freesco box as their gateway, which in
turn routes the traffic to it's gateway (the modem).
DNS servers would be those of the ISP as I don't fancy running a DNS server
at home (yet).

Would this work at all and if so, is it the correct way of doing things?
Also, what would I use as the subnet mask? Would 255.255.255.0 work?

A big thanks to anybody who can offer help with this, I've been looking
forward to having a real network at home for ages...

Cheers,

Treefrog

On Tue, 11 Nov 2003 13:38:42 UTC, "Treefrog"
<(E-Mail Removed)> wrote:

> local ISP where I get as many static IP addresses as I want.
>
> My old Freeserve setup consisted of a Zoom ADSL router/firewall (the "X4" I
> think) connected via ethernet to an 8 port hub. The router had the address
> 192.168.0.1 and the other computers were 192.168.0.2/3/4 etc. This was kind
> of okay but the router's firewall is crap and required a reboot (thus new IP
> address) whenever I wanted to change the rules, which was quite often as I
> like experimenting a lot.
>
> With my new setup I want every machine on my home LAN to have it's own
> (class c?) IP address but I don't know much about this sort of thing. I want
> to do something like this:

Let's assume your ISP gives you 16 addresses (plus one for the WAN
address of the router, which is pretty irrelevant). Let's assume they
are 299.99.99.208 to 299.99.99.223 (impossible invented addresses;
substitute the block you've been given).

The router has a WAN address as assigned (dynamic, maybe). Set its LAN
address to (say) 192.168.1.1 (yes, really this address). Set it to route
between its two interfaces of course, if you need to put actual IP
addresses in there.

> [MYISP] <> [ADSL MODEM] <> [FREESCO BOX] <> {LAN}{WITH}{MANY}{MACHINES}

Easy, now. Give the Freesco box two addresses. The router side gets
192.168.1.2, and the other side gets an address on your LAN. Use
299.99.99.209 (...208 is the network address, being the lowest one in
the block); conventionally the second address is the router address but
it doesn't really matter. Obviously, again, it'll route between its two
interfaces subject to the firewall rules, and you'll have to put in
routes to do that.

Now give your LAN machines other static addresses (...210 up to ...222;
...223 is the broadcast address). And the subnet address is that which,
when masked with any static IP address, gives the network address. So in
this example it'll be 299.99.99.240.

Set the default route on every LAN machine (except the Freesco box) to
point to 299.99.99.209.

The hub obviously has all the LAN machines and the Freesco box on it.
You need a crossover cable between the Freesco box and the router
(usually; depends on the router).

> A big thanks to anybody who can offer help with this, I've been looking
> forward to having a real network at home for ages...

This is the exact setup I've been using for 18 months. Except that my
firewall box isn't Freesco (or any flavour of UNIX, come to that).

Only downside is that you can't connect to the Internet from the Freesco
box because it's IP address is only locally legal. You also can't have
anything else on the DMZ network (the twisted cable *is* the network)
that talks to the outside world. This can be fixed by getting a second
static block (say a /29, 8 addresses) from your ISP and using one for
Freesco, one for router, and the other four for any servers you want to
put in the DMZ.

Hope this is clear. Feel free to ask. The email address above IS valid.
So is the one below.
--
Bob Eager
rde at tavi.co.uk
PC Server 325*4; PS/2s 9585, 8595, 9595*2, 8580*3,
P70...

"Treefrog" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hi,
>
> Two weeks after moving house, I've finally got ADSL again (last night),
it's
> been a painfull & slow two weeks and I'm glad to be on this side of it.
;o)
> I swapped from using Freeserve and the accompanying DHCP to using a
friendly
> local ISP where I get as many static IP addresses as I want.
>
> My old Freeserve setup consisted of a Zoom ADSL router/firewall (the "X4"
I
> think) connected via ethernet to an 8 port hub. The router had the address
> 192.168.0.1 and the other computers were 192.168.0.2/3/4 etc. This was
kind
> of okay but the router's firewall is crap and required a reboot (thus new
IP
> address) whenever I wanted to change the rules, which was quite often as I
> like experimenting a lot.
>
> With my new setup I want every machine on my home LAN to have it's own
> (class c?) IP address but I don't know much about this sort of thing. I
want
> to do something like this:
>
> [MYISP] <> [ADSL MODEM] <> [FREESCO BOX] <> {LAN}{WITH}{MANY}{MACHINES}
>
> The ADSL modem will be my existing Zoom router with forwarding ALL ports
> (DMZ feature on the Zoom) to the Freesco machine (I have a cobalt qube but
> no PSU, gutted). The way I thought it would work (pure guess work) is:
> The router/modem would have the IP (obviously made up here) 212.99.99.1
> which would be the gateway for eth0 on the freesco box, eth1 would be
> connected to the hub. All the machines LAN side would be assigned
> 212.99.99.x addresses and use the freesco box as their gateway, which in
> turn routes the traffic to it's gateway (the modem).
> DNS servers would be those of the ISP as I don't fancy running a DNS
server
> at home (yet).
>
> Would this work at all and if so, is it the correct way of doing things?
> Also, what would I use as the subnet mask? Would 255.255.255.0 work?
>
> A big thanks to anybody who can offer help with this, I've been looking
> forward to having a real network at home for ages...
>
Hi
This very similar to what I have run for some time. I use old IBM desktop
runing
e-smith. this is a free Linux gateway router. email server and local
intranet for shared drives.
It also can support fax as well with added software.

The set up is

ISP-->Router---->e-Smith---->network

At the moment the router is a wireless one but the wireless clients can only
see the internet and the public facing side of the server. This means I can
check my mail when away via the webmail interface.

as to addressing

215.123.123.321 ROUTER <192.168.0.1> --<192.168.0.2> E-SMITH <192.168.10.1>
LAN 192.168.10.100 Upwards

All machines have their Ip addresses asigned by DHCP from the server and
thier Gateway is the interface of the server they see. 192.168.10.1 Their
DNS is the internet one. But esmith does cache pages. using squid.

The system also now filters email to block emails with defined attachments.

If you want more info email me

Ian

www.cyber-cottage.co.uk
www.bathford-broadband.co.uk

"Treefrog" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> Hi,
>
> Two weeks after moving house, I've finally got ADSL again (last night),
it's
> been a painfull & slow two weeks and I'm glad to be on this side of it.
;o)
> I swapped from using Freeserve and the accompanying DHCP to using a
friendly
> local ISP where I get as many static IP addresses as I want.
>
> My old Freeserve setup consisted of a Zoom ADSL router/firewall (the "X4"
I
> think) connected via ethernet to an 8 port hub. The router had the address
> 192.168.0.1 and the other computers were 192.168.0.2/3/4 etc. This was
kind
> of okay but the router's firewall is crap and required a reboot (thus new
IP
> address) whenever I wanted to change the rules, which was quite often as I
> like experimenting a lot.
>
> With my new setup I want every machine on my home LAN to have it's own
> (class c?) IP address but I don't know much about this sort of thing. I
want
> to do something like this:
>
> [MYISP] <> [ADSL MODEM] <> [FREESCO BOX] <> {LAN}{WITH}{MANY}{MACHINES}
>
> The ADSL modem will be my existing Zoom router with forwarding ALL ports
> (DMZ feature on the Zoom) to the Freesco machine (I have a cobalt qube but
> no PSU, gutted). The way I thought it would work (pure guess work) is:
> The router/modem would have the IP (obviously made up here) 212.99.99.1
> which would be the gateway for eth0 on the freesco box, eth1 would be
> connected to the hub. All the machines LAN side would be assigned
> 212.99.99.x addresses and use the freesco box as their gateway, which in
> turn routes the traffic to it's gateway (the modem).
> DNS servers would be those of the ISP as I don't fancy running a DNS
server
> at home (yet).
>
> Would this work at all and if so, is it the correct way of doing things?
> Also, what would I use as the subnet mask? Would 255.255.255.0 work?
>
> A big thanks to anybody who can offer help with this, I've been looking
> forward to having a real network at home for ages...
>
> Cheers,
>
> Treefrog
>
>

Thanks to Bob and Ian for the replies. Much appreciated. I've not had chance
to try it yet as I'm having difficulty finding enough working spare parts to
build my router - it's nearly done, just trying to find a HD that is bigger
than 50meg (man, I collect crap)!

A final question, if I may, can somebody recomend a good place/book (not
TCP/IP illustrated, I'm not that rich ;o) to learn about IP address
allocation? I have no idea how to calculate what the subnet should be for a
given IP range, I think knowing that would make building networks just a
touch easier for me ;o)

Thanks,

Treefrog

On Thu, 13 Nov 2003 15:13:17 UTC, "Treefrog"
<(E-Mail Removed)> wrote:

> A final question, if I may, can somebody recomend a good place/book (not
> TCP/IP illustrated, I'm not that rich ;o) to learn about IP address
> allocation? I have no idea how to calculate what the subnet should be for a
> given IP range

An IP address is four bytes, with each expressed in decimal, e.g.:

192.168.42.20

If you're given a block of addresses, you'll only ever have the bottom
(R/hand) byte differing (unless you have more than 256 addresses in the
block!). So they would go:

192.168.42.20
192.168.42.21
192.168.42.22
192.168.42.23

Blocks are always a power of two, so you'd have 4, 8, 16, 32, ... (1 and
2 are not much use) as the firts address. They always start on a
multiple of that value, so a block of 4 would be 192.168.42.4, ...8,
...12, etc. It could never start at (say) ...10 or ..14.

The subnet mask is set to 255.255.255.xxx, where xxx is 256 minus the
power of two (the size of the block) you are using. So, for a block of 8
addresses it would be 248, for a block of 16 it would be 240, etc.

Hopefully that example (limited, but enough for your purposes) will save
you buying the book!

--
Bob Eager
rde at tavi.co.uk
PC Server 325*4; PS/2s 9585, 8595, 9595*2, 8580*3,
P70...

* treefrog wrote:
> A final question, if I may, can somebody recomend a good place/book (not
> TCP/IP illustrated, I'm not that rich ;o) to learn about IP address
> allocation? I have no idea how to calculate what the subnet should be for a
> given IP range, I think knowing that would make building networks just a
> touch easier for me ;o)

This is easy. An IP (v4) address is a 32-bit number, conventionally
written as a sequence of four 8-bit numbers, or octets, expressed in
decimal, with the leftmost being most significant. So, say
192.168.0.1 is actually

11000000 01111110 00000000 00000001
^^^^^^^^ ^^^^^^^^ ^^^^^^^^ ^^^^^^^^
192 168 0 1

Some portion of the left of this address represents the network
number, and the rest represents the host address within the network.
Once upon a time there were only three places where the break could
take place - there'd either be an 8, 16 or 24 bit network number,
known as class A, B or C. And further addresses were categorised as
A, B or C networks based on the first octet (the 192 here). Nowadays
the network/host break can be anywhere in the address, and where it is
is something you have to know, you can't guess it from the address.

There are two ways of specifying the network/host division. One is to
give a length qualifier on the address: 192.168.0.0/24 means this is
an address of which the first 24 bits are network and the rest are
host:

11000000 01111110 00000000 00000000
^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^
network host

The other is to specify a netmask, which is an IP address which is all
1s in the network and all 0s in the host: 192.168.0.0 netmask
255.255.255.0 means:

11000000 01111110 00000000 00000000
11111111 11111111 11111111 00000000
^^^^^^^^^^^^^^^^^^^^^^^^^^ ^^^^^^^^
network host

And you can see that this is the same thing.

Within a given network, host numbers go from all zeros to all 1s, with
the `zeros address' and the `1s address' not being usable. (The zeros
is the network number, and the 1s address is the broadcast address: to
complicate things the zeros address was once interpreted by some
systems as the broadcast address, which is another reason not to use
it). This means that, for instance, a /24 network (class C in old
speak) will always have a last octet of zero for instance.

It also means that for a /nn network there will be 2^(32 - n) - 2
usable hosts (where the `- 2' comes from subtracting out the 0s and 1s
addresses). So for a /24 network, there are 2^(32 - 24) - 2 = 2^8 - 2
= 254 hosts.

Things get harder to understand if you're looking at network numbers
which do not start on octet boundaries. Our current address range is a /28,
and the network number is 212.240.242.96 for instance. Drawing this
in binary you get:

Dec addr 212 240 242 98
Address 11010100 11110000 11110010 01100000
Mask 11111111 11111111 11111111 11110000
Dec mask 255 255 255 240

You can see that the trailing four bits are 0s which is as they should
be. But, for instance, a network number of 212.240.242.98/28 doesn't
make sense because 98 is 1100010 in binary, and this doesn't make
sense as a network number for a /28 network (it would make sense as a
number for a /31 network, but that has no usable hosts: there's only a
network and a broadcast address).

So in other words, for a size of network, the network numbers can only
start on certain values. The easy ones are things like /24 which
start on octet boundaries: the possible /24 networks are all the
x.y.z.0 numbers. But for non octet boundaries it's harder: you can
write down what the network numbers can be (for a /n network the
possible network numbers are x^2(32-n) for x from 1 to 2^n I think),
but it's often easiest to just draw pictures as above.

--tim

"Tim Bradshaw" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed)...
> * treefrog wrote:
> > A final question, if I may, can somebody recomend a good place/book (not
> > TCP/IP illustrated, I'm not that rich ;o) to learn about IP address
> > allocation? I have no idea how to calculate what the subnet should be
for a
> > given IP range, I think knowing that would make building networks just a
> > touch easier for me ;o)
>
> This is easy. An IP (v4) address is a 32-bit number, conventionally
> written as a sequence of four 8-bit numbers, or octets, expressed in


Bob and Tim,

Thank you for your excellent replies. The world needs more people like you.

I think that's my Friday night reading sorted ;o)

Thanks Again,

Treefrog