Unix Guide Page 22

IGP (Interior Gateway Protocol) – This protocol deals with the inside of the network. For use with smaller networks
EGP (Exterior Gateway Protocol) – This protocol deals with the outside of the network (usually), between routers of different networks

Some Routing Protocols
IGP Protocols	EGP Protocols
Rip (Routed Internet Protocol)	OSPF (Open Shortest Path First)
	CIDR (Classless Interdomain Routing)
Rdisc
	EGP (Exterior Gateway Protocol)

Sun Solaris provides in.rdisc to support rdisc, in.routed to support RIP. gate.d (not provided) supports all protocols.

Comparison of RIP and Rdisc
Rip	Rdisc
Broadcast message sent to all 30 second (periodic) updates Network routes Less work for router Everyone supports	Multicast messages sent to all subscribers 10 minute (periodic) and solicitation updates default routes (also sees host routes through ICMP redirect) Less work for host Only Sun supports (as of Solaris 2.6)

In TCP/IP addressing there are 5 classes of addresses. They are as listed in the following table:

IP Address Classes
Class of Address	Network and Node Portion of IP	First Octet of Address
Class A	N.H.H.H	1 - 126
Class B	N.N.H.H	128 - 191
Class C	N.H.H.H	192 - 223
Class D	N.N.N.N	224 - 239 (multicast)
Class E		Research
N = Network portion, H = Host portion

The classes have to do with what the network and node numbers are. You can tell what the class of address is by looking at the first octet number, so an IP of 12.0.0.0 would be a class A address. A standard IP address has four 8 bit octet sets, for instance: 192.168.0.23 or 10.0.0.45

In a Class A address you have only 1 network number and 3 host numbers, and the network number is the first. So for the address 10.0.0.45, the 10 is the network number, and the 0.0.45 is the host IP number. A Class B address has 2 network numbers and 2 hosts, so for the IP address 190.168.233.98, the 190.168 is the network number and the 233.98 is the host IP address. In a Class C address, the first 3 octets are the network numbers, and the last number is the host number. A Class A network is for very large networks (like ISP’s), while most people get a Class C, because for each network, you will only have 254 hosts (nodes). The network number is always assigned by the InterNic, while the host or node number is assigned by the administrator.