Network Technology 1 4th - Subnet.! Mario Lombardo -

Transcription

1 Network Technology 1 4th - Subnet Mario Lombardo - lombardo@informatik.dhbw-stuttgart.de 1

2 logical networks An IP address is divided into: - network address part - host address part - both parts together are the Internet Address - hosts having the same network address part are in the same logical network - within a network each address does exist one time only - router are connecting hosts configured for different network addresses 2

3 logical networks An IPv4 address has a size of 4 bytes IPv4 addresses are visualized as four octets (0 255) Example: This address is divided into two parts: The network address is the host address is 8. Where to split the address? 3

4 logical networks Kinds of networks - Classful Networks RFC Classless Networks (seit 1993) RFC 1518, RFC

5 classful networks classification into five segments class A ( hosts per segment) class B ( hosts per segment) class C (254 hosts per segment) class D (multicast addresses) class E (reserved) Class A: Class B: Class C: Class D: Class E:

6 classful networks examples for early assigned networks (General Electric) (IBM) (AT&T) (Xerox) (Hewlett Packard) (former DEC, now HP) (Apple) (MIT, Hochschule) (Ford) 6

7 classful networks classful networks the binary mask of the first octet defines the split of network part and host part 0XXX XXXX to (0 to 127 decimal) first octet for net part only the octets 2 to 4 available for hosts class A 10XX XXXX to (128 to 191 decimal) first and second octet for net part the octets 3 and 4 available for hosts class B 110X XXXX to (192 to 223 decimal) first to third octet for net part the octet 4 is available for hosts class C 7

8 classless networks Classless Inter-Domain Routing (CIDR) introduced 1993 to gain a more flexible network separation RFC 1518 and RFC 1519 introduction of a mask to divide network part and host part net mask has size of address (32 bit for IPv4) net mask is filled by 1 from the highest bit to the lowest (equals class A)

9 classless networks Classless Inter-Domain Routing (CIDR) an IP address is combined with a mask (subnet mask) Address: Net Mask: all bits ANDed Network ID: all zero-bits in the net mask can be used for host addressing host address 001 in theory addresses starting from 000 to 255 are valid; however as the first address is reserved for the network ID, this is remaining for hosts first host address: last host address: the last address in a network is reserved too (255) 9

10 broadcasting broadcast last address within a network segment is the broadcast address sending data to the broadcast address reaches each member in the network the directed broadcast is most common : all hosts from to (in case of class C / net mask ) : all hosts from to (in case of class A / net mask ) with a net mask the BC is for hosts to the limited Broadcast is unspecified address is used this kind of broadcast is not routable locally converted to Ethernet broadcast 10

11 private networks each class has a reservation for private usage RFC 1597 (first description, deprecated by RFC 1918) private addresses are not assigned within the internet class A: (one class A network segment) class B: to (16 class B network segments) class C: to (256 class C network segments) local link: (one class B network segment, RFC 3330) as there is no system listening in the internet everybody can use them without restriction today private addresses are common because of the shortage of IPv4 address space 11

12 spelling an address without net mask can be treated as classful network once a net mask is provided this overwrites the class a mask can be provided like the address (for IPv4) net mask: the mask can also be provided as a prefix (short for prefix-length) /8 this number equals the amount of 1 in the net mask 12

13 thank you questions? 13