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Unformatted text preview: the datagram is sent directly to
the destination, or a default router is chosen.
Hosts and routers have a routing table that is used for all routing decisions. There are three types of
routes in the table: host specific, network specific, and optional default routes. There is a priority to
the entries in a routing table. A host route will be chosen over a network router, and a default route
is used only when no other route exists to the destination.
IP routing is done on a hop-by-hop basis. The destination IP address never changes as the datagram
proceeds through all the hops, but the encapsulation and destination link-layer address can change
on each hop. Most hosts and many routers use a default next-hop router for all nonlocal traffic.
Class A and B addresses are normally subnetted. The number of bits used for the subnet ID is file:///D|/Documents%20and%20Settings/bigini/Docu...homenet2run/tcpip/tcp-ip-illustrated/ip_inter.htm (18 of 19) [12/09/2001 14.46.37] Chapter 3. IP: Internet Protocol specified by the subnet mask. We gave a detailed example of this, using the author's subnet, and
introduced variable-length subnets. The use of subnetting reduces the size of the Internet routing
tables, since many networks can often be accessed through a single point. Information on the
interfaces and networks is available through the ifconfig and netstat commands. This
includes the IP address of the interface, its subnet mask, broadcast address, and MTU.
We finished the chapter with a discussion of potential changes to the Internet protocol suite-the
next generation of IP.
3.1 Must the loopback address be 127.0.0.1?
3.2 Identify the routers in Figure 3.6 with more than two network interfaces.
3.3 What's the difference in the subnet mask for a class A address with 16 bits for the subnet ID
and a class B address with 8 bits for the subnet ID?
3.4 Read RFC 1219 [Tsuchiya 1991] for a recommended technique for assigning subnet IDs and
3.5 Is the subnet mask 255.255.0.255 valid for a class A add...
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This test prep was uploaded on 04/04/2014 for the course ECE EL5373 taught by Professor Guoyang during the Spring '12 term at NYU Poly.
- Spring '12