[4004] in linux-net channel archive
Re: Subnetting, Arghh
daemon@ATHENA.MIT.EDU (Matthias Urlichs)
Sun Aug 11 18:39:32 1996
From: Matthias Urlichs <smurf@smurf.noris.de>
To: linux-net@vger.rutgers.edu
Date: Sat, 10 Aug 1996 15:54:49 +0100
In linux.dev.net, article <9608090841.ZM2966@extacy>,
"Randall Shutt" <rshutt@extacy.ravenet.com> writes:
>=20
> You pretty much have a rigid set of choices. Either 2 nets of 6=
4 usable,
> or 6 nets of 30 usuable. There are plenty beyond that, but I think t=
he 30 is
> your case. Here is what the mappings would look like:
>=20
Which is somewhat out of date.
First, the subnets with all-zeroes and all-ones,
> Zeroth subnet =3D 00000000 - 00011111
> 32 63
> [...]
> Seventh subnet =3D 11100000 - 11111111
> 192 - 223
are no longer forbidden. The RFC which mandated that was a mistake, as =
the
subnets are invisible from the outside anyway.
Secondly, nobody (*) prevents you from having variable subnet masks, eg=
.
some.net.addr.0000xxxx with 14 hosts (netmask: 255.255.255.240)
some.net.addr.0001xxxx with 14 hosts (netmask: 255.255.255.240)
some.net.addr.001xxxxx with 30 hosts (netmask: 255.255.255.224)
some.net.addr.01xxxxxx with 60 hosts (netmask: 255.255.255.192)
some.net.addr.1xxxxxxx with 126 hosts (netmask: 255.255.255.128)
Likewise, nothing at all prevents you from running one or more of the a=
bove
on the same Ethernet. You don't even need to give your Linux systems mo=
re
than one address. You can't do _that_ with a Cisco router. ;-)
(*): OK, OK -- stupid, out-of-date, plain-and-simply _broken_ routers a=
nd
routing protocols, but that's not a problem with the Linux network=
ing
code, which deals with these things perfectly.
--=20
Un tien vaut miex que deux tu l`auras.
=20
(A bird in the hand is worth two in the bush.)
--=20
Matthias Urlichs \ noris network GmbH / Xlink-POP N=FCrnberg=
=20
Schleiermacherstra=DFe 12 \ Linux+Internet / EMail: urlichs@nor=
is.de
90491 N=FCrnberg (Germany) \ Consulting+Programming+Networking+etc=
'ing
PGP: 1024/4F578875 1B 89 E2 1C 43 EA 80 44 15 D2 29 CF C6 C7 E0 D=
E
Click <A HREF=3D"http://info.noris.de/~smurf/finger">here</A>. =
42
