| Solaris uses a memory-based table to store information on how to route packets to different destinations. There are two types of route ”direct and indirect: -
Direct ” A direct route exists when two (or more) hosts are connected to the same physical network and the two hosts can exchange information without any other device being involved. If you wrote a letter, for example, to your next door neighbor, you would simply deliver the letter to the house; there would be no need to involve the postal system. -
Indirect ” An indirect route exists when two (or more) hosts are not connected to the same physical network. For communication to take place, an intermediate device is required that is connected to both the source and destination networks. If you wrote a letter, for example, to a friend in another state, you would use the postal system to deliver the letter because the postal system knows how to get the letter to the destination and can do so efficiently . The routing table is populated with entries that determine how to forward packets to the destination. The entries can be either static or dynamic, as described here: -
Static ” Static routes, as the name implies, are permanent entries in the routing table. These entries can only be removed manually. A number of static routes are added to the route table when a system boots; these are for networks that are directly connected to the installed network interfaces, the multicast address, and the loopback address. You can add other static routes to non-local networks by using the command line, but they do not persist across reboots of the system and have to be added again when the system comes back up. A disadvantage of static routes is that, because of the fixed nature of these routes, communication with the destination host or network can be lost by the failure of the device being used to route the packets. -
Dynamic ” Dynamic routes, as the name implies, can change depending on information provided by processes such as in.routed and in.rdisc , both of which are discussed later in this chapter. The routing table is updated regularly with information about networks that can be reached ”this information is received from other routers advertising known routes on the network. Dynamic routing has the advantage of providing resilience when more than one route exists between two destinations, because if one route becomes inaccessible, the other is used automatically. Using dynamic routing, routers advertise on the network about networks they know about. Other hosts on the network "listen" to these advertisements and update their own routing tables according to the latest information.  |
