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From: causse@sphynx.fdn.fr (Philippe Causse)
Subject: Re: User PPP
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Message-ID: <EAL93r.BH@sphynx.fdn.fr>
References: <Pine.BSI.3.95.970519184616.5906A-100000@gold.interlog.com> <86g1vgfj10.fsf@bitbox.follo.net>
Date: Thu, 22 May 1997 15:16:39 GMT
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Xref: euryale.cc.adfa.oz.au comp.unix.bsd.freebsd.misc:41433
Eivind Eklund (perhaps@yes.no) wrote:
: In article <EAHuFC.xy@sphynx.fdn.fr> causse@sphynx.fdn.fr (Philippe Causse) writes:
: >
: > Brian Somers (brian@shift.utell.net) wrote:
: > > You should be using 192.168.0.0/16 - not 192.0.0.0/8 :)
: >
: > I thought 192.168.x.x was a class C network address, so the netmask
: > should be 255.255.255.0, not 255.255.0.0.
: It is 4 C-net's, if I remember correctly - 192.168.0/1/2/3. In other
: word, 22 bits of mask - 255.255.252.0
I don't understand exactly what you mean...
If 4 class C networks were in use, and you're willing to expand the netmask
then it should be something between 24 bits and 24 + (8-2) = 30 bits.
(since only the last two bits are significant for the host addressing).
Now, yet another digression about the 192.168.X.X well known address...
Reading the default /etc/hosts, I see:
192.168.0.0 to 192.168.255.255 = Class C
and the statement above says: "According to RFC1918, you can use the following
addresses for private nets... blah blah."
Clearly, there are 3 kinds of classes: A, B and C.
The "A" class uses 8 bits for net, 24 bits for host
B 16 16
C 24 8
(I ommit the class D network which is reserved for multicast addresses).
This scheme perfectly fits the constants defined in <netinet/in.h>, so
I honestly doubt that a netmask could be 22 bits !
BTW, in practice you may use a netmask greater than the "official" one,
especially on sub-subnets. This is particulary useful with routers in
a class B environment...
Experience showed that even a 32bits mask (0xFFFFFF) is acceptable and
(imho a good thing to do) for point to point connections.
: Eivind.
Regards,
Philippe.
--
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P. Causse http://www.fdn.fr/~pcausse
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