If IP-address and Netmask are inconsistent

Alex Vinokur

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Mar 5, 2002, 8:00:38 AM3/5/02

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============================
pRISM+ for pSOSystem/PowerPC
pRISM+ 1.2.3 . pSOSystem 2.2.2
Diab Data D-CC Optimizing C compiler (Version 4.1a)
Host : Windows98
Target : PowerPC (MPC860)
============================

Here is some IP-address and Netmask using in target :
IP-address = 192.168.0.77
NetMask = 255.255.0.0

It seems that they are inconsistent, because
IP-address belongs to Class C, so its HostId contains 8 bits.
However, NetMask 255.255.0.0 allows 16 bits for HostId.

Does pSOS (or another RTOS) have to check such inconsistency?

Does pSOS check it?

===========================
Alex Vinokur
mailto:ale...@bigfoot.com
mailto:ale...@yahoo.com
http://up.to/alexvn
http://go.to/alexv_math
===========================

Tauno Voipio

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Mar 5, 2002, 8:18:48 AM3/5/02

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"Alex Vinokur" <ale...@bigfoot.com> wrote in message
news:3C84C176...@bigfoot.com...

> ============================
> pRISM+ for pSOSystem/PowerPC
> pRISM+ 1.2.3 . pSOSystem 2.2.2
> Diab Data D-CC Optimizing C compiler (Version 4.1a)
> Host : Windows98
> Target : PowerPC (MPC860)
> ============================
>
> Here is some IP-address and Netmask using in target :
> IP-address = 192.168.0.77
> NetMask = 255.255.0.0
>
> It seems that they are inconsistent, because
> IP-address belongs to Class C, so its HostId contains 8 bits.
> However, NetMask 255.255.0.0 allows 16 bits for HostId.
>

No problem - this is perfectly OK for CIDR (Classless Internet Domain
Routing).

Besides - there are 65536 addresses in the 192.168.x.y network.

Tauno Voipio
tauno voipio @ iki fi

NOS...@rigney.org

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Mar 5, 2002, 11:13:03 AM3/5/02

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In comp.protocols.tcp-ip Alex Vinokur <ale...@bigfoot.com> wrote:
> ============================
> pRISM+ for pSOSystem/PowerPC
> pRISM+ 1.2.3 . pSOSystem 2.2.2
> Diab Data D-CC Optimizing C compiler (Version 4.1a)
> Host : Windows98
> Target : PowerPC (MPC860)
> ============================
>
> Here is some IP-address and Netmask using in target :
> IP-address = 192.168.0.77
> NetMask = 255.255.0.0
>
> It seems that they are inconsistent, because
> IP-address belongs to Class C, so its HostId contains 8 bits.

Only by RFC and convention. It's up to you to follow best
practices.

> However, NetMask 255.255.0.0 allows 16 bits for HostId.
>
> Does pSOS (or another RTOS) have to check such inconsistency?
>
> Does pSOS check it?
>

If you want it to check for RFC compliance, you need to code
for that.

-parc

p...@icke-reklam.ipsec.nu

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Mar 5, 2002, 1:29:33 PM3/5/02

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In comp.protocols.tcp-ip Alex Vinokur <ale...@bigfoot.com> wrote:

> ============================
> pRISM+ for pSOSystem/PowerPC
> pRISM+ 1.2.3 . pSOSystem 2.2.2
> Diab Data D-CC Optimizing C compiler (Version 4.1a)
> Host : Windows98
> Target : PowerPC (MPC860)
> ============================

> Here is some IP-address and Netmask using in target :
> IP-address = 192.168.0.77
> NetMask = 255.255.0.0

> It seems that they are inconsistent, because
> IP-address belongs to Class C, so its HostId contains 8 bits.
> However, NetMask 255.255.0.0 allows 16 bits for HostId.

These is no inconsistenvu in the figures alone.

What you describe is a machine with an ip-address of 192.168.0.77
located on a network with 65535 possible hosts .

The netmask is used to describe how many hosts are directly reachable
on the same LAN-segment ( using straight cables, hubs switches/bridges)

> Does pSOS (or another RTOS) have to check such inconsistency?

Again, there is no inconsistency. You have to tell how large your
local segment is.

> Does pSOS check it?

> ===========================
> Alex Vinokur
> mailto:ale...@bigfoot.com
> mailto:ale...@yahoo.com
> http://up.to/alexvn
> http://go.to/alexv_math
> ===========================

--
Peter Håkanson
IPSec Sverige (At the Riverside of Gothenburg, home of Volvo)
Sorry about my e-mail address, but i'm trying to keep spam out.
Remove "icke-reklam" and it works.

James Carlson

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Mar 11, 2002, 7:30:08 AM3/11/02

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Alex Vinokur <ale...@bigfoot.com> writes:
> Here is some IP-address and Netmask using in target :
> IP-address = 192.168.0.77
> NetMask = 255.255.0.0

OK; that's sometimes called a "supernet."

> It seems that they are inconsistent, because
> IP-address belongs to Class C, so its HostId contains 8 bits.
> However, NetMask 255.255.0.0 allows 16 bits for HostId.

No. That may have been true a very long time ago, but in the modern
world of CIDR, there's no such thing as a "Class C" address or a
natural netmask.

> Does pSOS (or another RTOS) have to check such inconsistency?
>
> Does pSOS check it?

If it does, it's broken.

--
James Carlson, Solaris Networking <james.d...@east.sun.com>
SUN Microsystems / 1 Network Drive 71.234W Vox +1 781 442 2084
MS UBUR02-212 / Burlington MA 01803-2757 42.497N Fax +1 781 442 1677