32
For example, all applications based on RPC use the loopback interface to register themselves with the portmapper daemon at startup. These applications include NIS and NFS.
33
Note that pointopoint is not a typo. It's really spelled like this.
34
As a matter of caution, you should configure a PLIP or SLIP link only after you have completely set up the routing table entries for your Ethernets. With some older kernels, your network route might otherwise end up pointing at the point-to-point link.
35
The dummy device is called dummy0 if you have loaded it as a module rather than choosing it as an inbuilt kernel option. This is because you are able to load multiple modules and have more than one dummy device.
36
More correctly, using IP aliasing is known as network layer virtual hosting. It is more common in the WWW and STMP worlds to use application layer virtual hosting, in which the same IP address is used for each virtual host, but a different hostname is passed with each application layer request. Services like FTP are not capable of operating in this way, and they demand network layer virtual hosting.
37
RIP chooses the optimal route to a given host based on the 'length' of the path. It is computed by summing up the individual metric values of each host-to-host link. By default, a hop has length 1, but this may be any positive integer less than 16. (A route length of 16 is equal to infinity. Such routes are considered unusable.) The metric parameter sets this hop cost, which is then broadcast by the routing daemon.
38
ssh can be obtained from ftp.cs.hut.fi in /pub/ssh.
39
You can tell whether a connection is outgoing from the port numbers. The port number shown for the calling host will always be a simple integer. On the host being called, a well-known service port will be in use for which netstat uses the symbolic name such as smtp, found in /etc/services.
40
If information weren't cached, then DNS would be as inefficient as any other method because each query would involve the root name servers.
41
Well, almost. A name server has to provide at least name service for localhost and reverse lookups of 127.0.0.1.
42
BIND 4.9 was developed by Paul Vixie, [email protected], but BIND is now maintained by the Internet Software Consortium, [email protected].
43
Note that you can't query your name server for the root servers if you don't have any root server hints installed. To escape this dilemma, you can either make nslookup use a different name server, or use the sample file in Example 6.10 as a starting point, and then obtain the full list of valid servers.
44
diplogin must be run as setuid to root, too. See the section at the end of this chapter.
45
Relevant RFCs are listed in the Bibiliography at the end of this book.
