One physical network - Two Class C networks?

One physical network - Two Class C networks?

Post by Larry Donah » Sat, 17 Dec 1994 04:02:51



I have a rather perplexing TCP/IP configuration question...

We have two Class C network addresses, 192.148.222.x and 204.130.218.x.
We have over 1,000 computers on one physical network, any of which could
use TCP/IP services.  We are attempting to implement a dynamic IP allocation
scheme, using BOOTP.

First question:  Does anyone know of a good BOOTP Server, under UNIX, that
handles dynamic IP allocation?  There is a Novell BOOTP server, an nlm, by
Hellsoft that does the job, but we need something for UNIX.

Second question:  We have had the 192.148.222.x Class C network for some
time.  Our netmask, of course, is 255.255.255.0.  Is it possible to use
the 204.130.218.x Class C network on the same physical network?  In my
mind, it seems possible with the right netmask and router.  We are directly
connected to the Internet via a Cisco Router.  Can anyone steer me in the
right direction to create the proper netmask and possible hardware purchase
to allow these two different Class C networks to exist on the same physical
network?

Any and all suggestions would be greatly appreciated.

Thanks.  Larry.

--
Laurence S. Donahue
Research Fellow, UNIX/Internet Consultant & Advisor
Chicago-Kent College of Law

(312)906-5308

Local URL:                        http://www.kentlaw.edu/~ldonahue/
The Legal Domain Network:         http://www.kentlaw.edu/lawnet/lawnet.html
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One physical network - Two Class C networks?

Post by Brian J. Murre » Sat, 17 Dec 1994 09:53:43




>I have a rather perplexing TCP/IP configuration question...

>We have two Class C network addresses, 192.148.222.x and 204.130.218.x.
>We have over 1,000 computers on one physical network, any of which could
>use TCP/IP services.  We are attempting to implement a dynamic IP allocation
>scheme, using BOOTP.

Hmmmm.  Not doable, strictly speaking.
Quote:

>First question:  Does anyone know of a good BOOTP Server, under UNIX, that
>handles dynamic IP allocation?  There is a Novell BOOTP server, an nlm, by
>Hellsoft that does the job, but we need something for UNIX.

There is none.  BOOTP is a direct mapping from MAC addresses to IP addresses.
You need something called DHCP (Dynamic Host Configuration Protocol), which
is much like BOOTP but does not have the 1 to 1 mapping.  Exactly what you
are looking for.  DHCP is quite new however, and you might be hardpressed
to find a server for it yet.  There is also the perplexing IP<->name mapping,
problem.  If a client gets it's IP address dynamically, how do you address
the machine by name.  What is really needed is a "runtime configurable"
DNS server, which you would be able to "inject" an IP<->name record into
as the IP address is assigned to the machine.
Quote:

>Second question:  We have had the 192.148.222.x Class C network for some
>time.  Our netmask, of course, is 255.255.255.0.  Is it possible to use
>the 204.130.218.x Class C network on the same physical network?  In my
>mind, it seems possible with the right netmask and router.  We are directly
>connected to the Internet via a Cisco Router.  Can anyone steer me in the
>right direction to create the proper netmask and possible hardware purchase
>to allow these two different Class C networks to exist on the same physical
>network?

No problem using more than on IP net on the same network.  You would have
to set up some routing on chosen machines if you want the machines in one
IP net to talk to the machines in the other IP net however.

Good luck,
b.

--


North Vancouver, B.C.                                             604 983 UNIX
        Platform and Brand Independent UNIX Support - R3.2 - R4 - BSD

 
 
 

One physical network - Two Class C networks?

Post by Larry Donah » Sun, 18 Dec 1994 01:26:52





> >I have a rather perplexing TCP/IP configuration question...

> >We have two Class C network addresses, 192.148.222.x and 204.130.218.x.
> >We have over 1,000 computers on one physical network, any of which could
> >use TCP/IP services.  We are attempting to implement a dynamic IP allocation
> >scheme, using BOOTP.

> Hmmmm.  Not doable, strictly speaking.

> >First question:  Does anyone know of a good BOOTP Server, under UNIX, that
> >handles dynamic IP allocation?  There is a Novell BOOTP server, an nlm, by
> >Hellsoft that does the job, but we need something for UNIX.

> There is none.  BOOTP is a direct mapping from MAC addresses to IP addresses.
> You need something called DHCP (Dynamic Host Configuration Protocol), which
> is much like BOOTP but does not have the 1 to 1 mapping.  Exactly what you
> are looking for.  DHCP is quite new however, and you might be hardpressed
> to find a server for it yet.  There is also the perplexing IP<->name mapping,
> problem.  If a client gets it's IP address dynamically, how do you address
> the machine by name.  What is really needed is a "runtime configurable"
> DNS server, which you would be able to "inject" an IP<->name record into
> as the IP address is assigned to the machine.

I heard about DHCP.  Your right about the problem, though.  DHCP is new and
I can't find a server for it.  Worse yet, the client software doesn't support
it.  I haven't read the RFC yet, but BOOTP does have the ability, if properly
configured.

Additionally, I don't see the IP<->Name as a problem.  DNS is configured
for that.  If you have 500 temporary hosts, you can configure all those
hosts in DNS.  When a machine starts up, the BOOTP program can furnish an
IP address and obtain the name from DNS.

Quote:> >Second question:  We have had the 192.148.222.x Class C network for some
> >time.  Our netmask, of course, is 255.255.255.0.  Is it possible to use
> >the 204.130.218.x Class C network on the same physical network?  In my
> >mind, it seems possible with the right netmask and router.  We are directly
> >connected to the Internet via a Cisco Router.  Can anyone steer me in the
> >right direction to create the proper netmask and possible hardware purchase
> >to allow these two different Class C networks to exist on the same physical
> >network?

> No problem using more than on IP net on the same network.  You would have
> to set up some routing on chosen machines if you want the machines in one
> IP net to talk to the machines in the other IP net however.

Let's see if I understand what you mean.  I can purchase another Ethernet
card for my Sun, and plug it in the wall.  In UNIX, the Ethernet interface
could become "le1" (for example).  Therefore, le0 and le1 would be on the
same physical network with two different ethernet hardware addresses.  I
could then configure a route in UNIX, so as to allow my machine to act as
a gateway between the two IP networks who happen to reside on the same
physical net?

Thanks for your help!

Larry.
--
Laurence S. Donahue
Research Fellow, UNIX/Internet Consultant & Advisor
Chicago-Kent College of Law

(312)906-5308

Local URL:                        http://www.kentlaw.edu/~ldonahue/
The Legal Domain Network:         http://www.kentlaw.edu/lawnet/lawnet.html
Chicago-Kent College of Law:      http://www.kentlaw.edu/

 
 
 

One physical network - Two Class C networks?

Post by Michael Dill » Sun, 18 Dec 1994 06:59:50





> >I have a rather perplexing TCP/IP configuration question...
> There is none.  BOOTP is a direct mapping from MAC addresses to IP addresses.
> You need something called DHCP (Dynamic Host Configuration Protocol), which
> is much like BOOTP but does not have the 1 to 1 mapping.  Exactly what you
> are looking for.  DHCP is quite new however, and you might be hardpressed
> to find a server for it yet.  

FTP software currently sells a DHCP server that runs on a PC
running DOS/Windows. I believe it is bundled in with their NFS server

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One physical network - Two Class C networks?

Post by ad.. » Sat, 17 Dec 1994 04:20:17



Quote:> Second question:  We have had the 192.148.222.x Class C network for some
> time.  Our netmask, of course, is 255.255.255.0.  Is it possible to use
> the 204.130.218.x Class C network on the same physical network?  In my
> mind, it seems possible with the right netmask and router.  We are directly
> connected to the Internet via a Cisco Router.  Can anyone steer me in the
> right direction to create the proper netmask and possible hardware purchase
> to allow these two different Class C networks to exist on the same physical
> network?

Yes, you can have lots of class-c networks on a single router port.  If
someone is telling you they can't, have them look in the cisco config
manual at 'secondary addresses'.  Certain versions of cisco software may
have some limitations on putting multiple Class-C's on a single port if
they have different subnet masks.  (ie, all subnet masks have to be exactly
the same for every class-* assigned to a single port).
 
 
 

One physical network - Two Class C networks?

Post by Phillip Vand » Mon, 19 Dec 1994 03:44:06



>> No problem using more than on IP net on the same network.  You would have
>> to set up some routing on chosen machines if you want the machines in one
>> IP net to talk to the machines in the other IP net however.
>Let's see if I understand what you mean.  I can purchase another Ethernet
>card for my Sun, and plug it in the wall.  In UNIX, the Ethernet interface
>could become "le1" (for example).  Therefore, le0 and le1 would be on the
>same physical network with two different ethernet hardware addresses.  I
>could then configure a route in UNIX, so as to allow my machine to act as
>a gateway between the two IP networks who happen to reside on the same
>physical net?

Look at our Sun with 2 Ethernet interfaces:

le0: flags=863<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST> mtu 1500
        inet 198.168.100.7 netmask ffffffe0 broadcast 198.168.100.31
        ether 8:0:20:12:bd:e2
le1: flags=863<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST> mtu 1500
        inet 198.168.73.132 netmask ffffff00 broadcast 198.168.73.255
        ether 8:0:20:12:bd:e2

Notice they have the same hardware address. This doesn't matter to us
since they are on different segments, mut in the case of the above,
it does. I think our ethernet card uses the assumption that you won't
but it on the same segment as the motherboard interface to allow it
to use the same hardware address.

Something to be careful about, if you intend to do this.

-Phil

 
 
 

One physical network - Two Class C networks?

Post by Erick Rudi » Mon, 19 Dec 1994 09:47:21




>>Let's see if I understand what you mean.  I can purchase another Ethernet
>>card for my Sun, and plug it in the wall.  In UNIX, the Ethernet interface
>>could become "le1" (for example).  Therefore, le0 and le1 would be on the
>>same physical network with two different ethernet hardware addresses.  I
>>could then configure a route in UNIX, so as to allow my machine to act as
>>a gateway between the two IP networks who happen to reside on the same
>>physical net?

>Look at our Sun with 2 Ethernet interfaces:

>le0: flags=863<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST> mtu 1500
>        inet 198.168.100.7 netmask ffffffe0 broadcast 198.168.100.31
>        ether 8:0:20:12:bd:e2
>le1: flags=863<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST> mtu 1500
>        inet 198.168.73.132 netmask ffffff00 broadcast 198.168.73.255
>        ether 8:0:20:12:bd:e2

>Notice they have the same hardware address. This doesn't matter to us
>since they are on different segments, mut in the case of the above,
>it does. I think our ethernet card uses the assumption that you won't
>but it on the same segment as the motherboard interface to allow it
>to use the same hardware address.

>Something to be careful about, if you intend to do this.

>-Phil

        How is the hardware address of your second (le1) ethernet card
determined?  Whenever I have seen a Sparc workstation boot, I see a
hardware address specified in the 'paragraph' right next to the psychedelic
Sun logo on the lefthand side.  I used to think that was the address of the
board, but I have seen machines with multiple network boards, all of which
assumed the same hardware address.  I kinda think that address might be in
PROM.  We have a very strict LAA scheme where I work and I put an 'ifconfig
tr0 ether AA:BB:CC:DD:EE:FF' statement in the rc.local script to redefine the
hardware address of the token ring (yes, I know, blech!!!) card in the
Sparc to adhere to our hardware address standards.  

        You are definitely correct that having two network devices with the
same hardware address on the same net can cause all sorts of havoc.  There
is a way around it, though.  You may want to be careful about putting the
ifconfig early enough in your script so that the second card does not come
up with an identical hardware address, although I don't think it would
cause -too- much trouble if it did.

--
+------------------------------------------------------------------------+
| Erick Rudiak          Licking an electrical outlet will NOT turn you   |

+------------------------------------------------------------------------+

 
 
 

One physical network - Two Class C networks?

Post by Casper H.S. D » Mon, 19 Dec 1994 20:02:49



>Let's see if I understand what you mean.  I can purchase another Ethernet
>card for my Sun, and plug it in the wall.  In UNIX, the Ethernet interface
>could become "le1" (for example).  Therefore, le0 and le1 would be on the
>same physical network with two different ethernet hardware addresses.  I
>could then configure a route in UNIX, so as to allow my machine to act as
>a gateway between the two IP networks who happen to reside on the same
>physical net?

It's better to have two IP addresses for teh same interface instead of
two interfaces on the same physical wire.

Easiest way to get two IP addrs on one interface in Solaris 2.x is:

        ifconfig le0:1  .....

If you have two interfaces on one wire, you'll have some problems:
less throughput (both interfaces can collide with eachother)
you need to pick a new MAC address for tehs econd interface (Sun gives all
interfaces the same MAC address).

The only time when more then one interface on a physical wire is desirable
is when you're using an ether switch that segments the ethernet.
(But then you're usually talking the same IP net)

Casper

 
 
 

One physical network - Two Class C networks?

Post by Rob McMah » Mon, 19 Dec 1994 20:25:00




>Let's see if I understand what you mean.  I can purchase another Ethernet
>card for my Sun, and plug it in the wall.  In UNIX, the Ethernet interface
>could become "le1" (for example).  Therefore, le0 and le1 would be on the
>same physical network with two different ethernet hardware addresses.  I
>could then configure a route in UNIX, so as to allow my machine to act as a
>gateway between the two IP networks who happen to reside on the same physical
>net?

Seems to me there's no need to buy a second Ethernet interface (which will
cause some confusion if they're both on the same bit of wire, as mentioned
elsewhere).  You can just use the

ifconfig le0:1 second_ip up

trick.

Cheers,

Rob

 
 
 

One physical network - Two Class C networks?

Post by de.. » Tue, 20 Dec 1994 15:50:45




> I have a rather perplexing TCP/IP configuration question...

> We have two Class C network addresses, 192.148.222.x and 204.130.218.x.
> We have over 1,000 computers on one physical network, any of which could
> use TCP/IP services.  We are attempting to implement a dynamic IP allocation
> scheme, using BOOTP.

> First question:  Does anyone know of a good BOOTP Server, under UNIX, that
> handles dynamic IP allocation?  There is a Novell BOOTP server, an nlm, by
> Hellsoft that does the job, but we need something for UNIX.

This sounds like a part of Novells' Lan Workgroup for DOS, where DOS clients
are automatically assigned an IP address during a DOS client installation
session and must rely on BOOTP thereafter.  I recommend using NIS or DNS for
maintaing IP addresses.

Quote:> Second question:  We have had the 192.148.222.x Class C network for some
> time.  Our netmask, of course, is 255.255.255.0.  Is it possible to use
> the 204.130.218.x Class C network on the same physical network?  In my
> mind, it seems possible with the right netmask and router.  We are directly
> connected to the Internet via a Cisco Router.  Can anyone steer me in the
> right direction to create the proper netmask and possible hardware purchase
> to allow these two different Class C networks to exist on the same physical
> network?

> Any and all suggestions would be greatly appreciated.

> Thanks.  Larry.

In regards to your second question - Is the physical network one large segment
containing both 192. & 204. logical networks, or hopefully it's divided into
subnets?  I'm going to assume that it's subdivided and that there is a router
separating the 192. and 204. subnets.

If the workstations on the 192. and 204. subnets in addition to the router is
configured for a routing protocol like RIP then the workstations on the
192. subnet will know what path to take to get to the 203. subnet and
viceversa.  The router will automatically update its routing table for both of
these subnets and no other configuration *should* be needed, for all practical
purposes.  You wouldn't need to worry about "the right netmask" since each
segment port on the router would be properly configured for that segment.

                     Internet    
                    -----+----
                         |<-- xxx.xxx.xxx.xxx (Official IP)
                +--------+--------+
                | Firewall router |
                +--------+--------+
                         |
                    +----+----+
 -------------------+ router  +--------------------
   192.148.222.xxx  +---------+  204.130.218.xxx
   192.148.222.0     netmasks    204.130.218.0

Your router product may be as simple as adding an option board into an existing
router, such as in the cisco's AGS+, or in the WellFleet's, etc.  If you need
to purchase an router the I would look into ciscos' offerings, great product
and support.

If the 192. and 204. logical networks are on the same physical wire than
there is no way traffic from the 192 will get to the 204. and viceversa.  
Subnet your network as shown above.

Good luck.
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One physical network - Two Class C networks?

Post by Larry Donah » Wed, 21 Dec 1994 01:41:01



>>Let's see if I understand what you mean.  I can purchase another Ethernet
>>card for my Sun, and plug it in the wall.  In UNIX, the Ethernet interface
>>could become "le1" (for example).  Therefore, le0 and le1 would be on the
>>same physical network with two different ethernet hardware addresses.  I
>>could then configure a route in UNIX, so as to allow my machine to act as a
>>gateway between the two IP networks who happen to reside on the same physical
>>net?

>Seems to me there's no need to buy a second Ethernet interface (which will
>cause some confusion if they're both on the same bit of wire, as mentioned
>elsewhere).  You can just use the

>   ifconfig le0:1 second_ip up

Sun told me I couldn't do that.  I'm running Solaris 2.3.  Where did you
get that information? (So I can tell Sun to stick it!)  ;-)

Thanks.  Larry.
--
Laurence S. Donahue
Research Fellow, UNIX/Internet Consultant & Advisor
Chicago-Kent College of Law

(312)906-5308

Local URL:                        http://www.kentlaw.edu/~ldonahue/
The Legal Domain Network:         http://www.kentlaw.edu/lawnet/lawnet.html
Chicago-Kent College of Law:      http://www.kentlaw.edu/

 
 
 

One physical network - Two Class C networks?

Post by Casper H.S. D » Wed, 21 Dec 1994 02:09:56



>>   ifconfig le0:1 second_ip up
>Sun told me I couldn't do that.  I'm running Solaris 2.3.  Where did you
>get that information? (So I can tell Sun to stick it!)  ;-)

It isn't documented, but it is works.  Some Sun engineer posted it
and the net never forgets.

Casper

 
 
 

One physical network - Two Class C networks?

Post by Jay Ashwor » Wed, 21 Dec 1994 05:12:49



)There is none.  BOOTP is a direct mapping from MAC addresses to IP addresses.
)You need something called DHCP (Dynamic Host Configuration Protocol), which
)is much like BOOTP but does not have the 1 to 1 mapping.  Exactly what you
)are looking for.  DHCP is quite new however, and you might be hardpressed
)to find a server for it yet.  There is also the perplexing IP<->name mapping,
)problem.  If a client gets it's IP address dynamically, how do you address
)the machine by name.  What is really needed is a "runtime configurable"
)DNS server, which you would be able to "inject" an IP<->name record into
)as the IP address is assigned to the machine.

Indeed it is.  I'm not sufficiently familiar with DHCP to know how you'd
do this.  Is there an RFC?

Cheers,
-- jra
--
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Designer             Linux: The Choice of a GNU Generation        & Associates
ka1fjx/4         "The difference between theory and practice   +1 813 790 7592

 
 
 

One physical network - Two Class C networks?

Post by Brian J. Murre » Wed, 21 Dec 1994 11:24:02



[ discussing the merits of DHCP ]
Quote:>)What is really needed is a "runtime configurable"
>)DNS server, which you would be able to "inject" an IP<->name record into
>)as the IP address is assigned to the machine.

>Indeed it is.  I'm not sufficiently familiar with DHCP to know how you'd
>do this.  Is there an RFC?

Not yet, I don't believe, but as DHCP becomes more popular, I'm sure there
will be one.

b.

--


North Vancouver, B.C.                                             604 983 UNIX
        Platform and Brand Independent UNIX Support - R3.2 - R4 - BSD

 
 
 

One physical network - Two Class C networks?

Post by Jim Merc » Wed, 21 Dec 1994 06:57:31







>> >First question:  Does anyone know of a good BOOTP Server, under UNIX, that
>> >handles dynamic IP allocation?  There is a Novell BOOTP server, an nlm, by
>> >Hellsoft that does the job, but we need something for UNIX.

>> There is none.  BOOTP is a direct mapping from MAC addresses to IP addresses.
>> You need something called DHCP (Dynamic Host Configuration Protocol), which
>> is much like BOOTP but does not have the 1 to 1 mapping.

there are not many DHCP servers implemented, more scary in my opinion, is
there is no reference implementation.  this means that each implementation is
going to be done based on the implementor's interpretation of the RFC's.

there is no benchmark to ensure compatibility.

i thought i'd seen some support for address pooling in one of the recent
bootp releases for unix.

in any case, here are some alternate suggestions if you want dynamic
bootp (not unix, but meant to be cost effective).

1) get a copy of Netware Runtime.  this is a Netware 3.11 server, but limited
to concurrent user 8^).   you can run the hellsoft or novell bootp server
on this using a 386SX with a 40 meg IDE drive.

2) get a copy of KA9Q.  i beleive that it supports dynamic bootp.  this can
be run on a 286 or better with a cheap ethernet card.  no hard drive required,
boots off a floppy.  (in a pinch, you _could_ do it on an 8086.

Quote:>Let's see if I understand what you mean.  I can purchase another Ethernet
>card for my Sun, and plug it in the wall.  In UNIX, the Ethernet interface
>could become "le1" (for example).  Therefore, le0 and le1 would be on the
>same physical network with two different ethernet hardware addresses.  I
>could then configure a route in UNIX, so as to allow my machine to act as
>a gateway between the two IP networks who happen to reside on the same
>physical net?

i don't see the problem.  i have suns, 386bsd's, ka9q's and other stuff
running on my network at home with multiple C classes on the same wire.

it doesn't require multiple interfaces, i just add a route for the
second C class pointing to the same interface, and poof, it works.

--

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