jessea@homecare.COM (Jesse W. Asher) (05/20/91)
Correct me if I'm wrong, but Class A-C networks depend on the number of
the first octet in the address. Class A is 1-127, Class B is 128-191,
and Class C is 192-223. What happens to 224-254? What are these being
used for, or are they being used for anything? Just a curious mind
wanting to know.
--
Jesse W. Asher NIC Handle: JA268 Phone: (901)386-5061
Health Sphere of America Inc.
5125 Elmore Rd., Suite 1, Memphis, TN 38134
Internet: jessea@homecare.COM UUCP: ...!banana!homecare!jesseaart@opal.acc.com (Art Berggreen) (05/20/91)
In article <1991May20.160942.24296@homecare.COM> jessea@homecare.COM (Jesse W. Asher) writes: >Correct me if I'm wrong, but Class A-C networks depend on the number of >the first octet in the address. Class A is 1-127, Class B is 128-191, >and Class C is 192-223. What happens to 224-254? What are these being >used for, or are they being used for anything? Just a curious mind >wanting to know. Its not actually the first octet, bit the first bits, as follows: 0XXXXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class A 10XXXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class B 110XXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class C 1110XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class D (Multicast) 1111XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Reserved Art
enag@ifi.uio.no (Erik Naggum) (05/21/91)
Jesse W. Asher writes: | | Correct me if I'm wrong, but Class A-C networks depend on the number of | the first octet in the address. Class A is 1-127, Class B is 128-191, | and Class C is 192-223. What happens to 224-254? What are these being | used for, or are they being used for anything? Just a curious mind | wanting to know. The Internet Numbers RFC [1] contains the authoritative reference on network numbers. Snipped from this vast RFC is the following: [2] The fourth type of address, class D, is used as a multicast address [13]. The four highest-order bits are set to 1-1-1-0. 1 2 3 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1 1 1 0| multicast address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Class D Address Note: No addresses are allowed with the four highest-order bits set to 1-1-1-1. These addresses, called "class E", are reserved. -------------- [3] Other Reserved Internet Addresses * Internet Address Network Reference - ---------------- ------- ---------- 224.000.000.000-239.255.255.255 Multicast [JBP] 240.000.000.000-255.255.255.255 Reserved [JBP] -------------- Hope this helps. </Erik> References: [1] RFC 1166 Kirkpatrick, S.; Stahl, M.K.; Recker, M. Internet numbers. 1990 July; 182 p. (Format: TXT=566778 bytes) (Obsoletes RFC 1117, RFC 1062, RFC 1020) [2] ibid, page 4 [3] ibid, page 100 -- Erik Naggum Professional Programmer +47-2-836-863 Naggum Software Electronic Text <enag@ifi.uio.no> 0118 OSLO, NORWAY Computer Communications <erik@naggum.uu.no>
enag@ifi.uio.no (Erik Naggum) (05/21/91)
Art Berggreen writes: | | Its not actually the first octet, bit the first bits, as follows: | | 0XXXXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class A | 10XXXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class B | 110XXXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class C | 1110XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Class D (Multicast) | 1111XXXX.XXXXXXXX.XXXXXXXX.XXXXXXXX Reserved I think it's easier if you present it with network and host numbers: 0nnnnnnn.hhhhhhhh.hhhhhhhh.hhhhhhhh Class A 10nnnnnn.nnnnnnnn.hhhhhhhh.hhhhhhhh Class B 110nnnnn.nnnnnnnn.nnnnnnnn.hhhhhhhh Class C 1110mmmm.mmmmmmmm.mmmmmmmm.mmmmmmmm Class D (multicast) 1111xxxx.xxxxxxxx.xxxxxxxx.xxxxxxxx Reserved Of course, then there's subnetting... </Erik> -- Erik Naggum Professional Programmer +47-2-836-863 Naggum Software Electronic Text <enag@ifi.uio.no> 0118 OSLO, NORWAY Computer Communications <erik@naggum.uu.no>
jason@hpcndjdz.CND.HP.COM (Jason Zions) (05/22/91)
Also, class A network 127 isn't a real assignable network, as any IP address on net 127 must be interpreted as a valid loopback address for the transmitting node. One should never see a packet on a network sent from or destined to net 127. Jazz