choose the type of firewall and IP masquerading to use. (You learned about IP
masquerading in the “Using IP Masquerading in Ubuntu” section, earlier in
this chapter.) The actual configuration is done automatically. Using a firewall
is essential, so choose this option unless you intend to craft your own set of
firewall rules (a discussion of which is beyond the scope of this book). After
you have chosen your firewall and IP masquerading setup, you are asked to
confirm, save, and implement your settings. You are also given a choice to
allow users to manage the connection, which is a handy option for home
users.
Changes are made to your system’s /etc/sysconfig/network-
scripts/ifcfg-ppp0, /etc /resolv.conf, /etc/ppp/pap-
secrets, and /etc/ppp/chap-secrets files.
After configuration has finished, use the adsl-start command to start a
connection and DSL session, like this:
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matthew@seymour:~$ sudo /sbin/adsl-start
The DSL connection should be nearly instantaneous, but if problems occur,
check to make sure that your DSL modem is communicating with the phone
company’s central office by examining the status LEDs on the modem. This
varies from modem to modem, so consult your modem user’s manual.
Make sure all cables are properly attached, that your interfaces are properly
configured, and that you have entered the correct information to the setup
script.
If IP masquerading is enabled, other computers on your LAN on the same
subnet address (such as 192.168.0.XXX) can use the Internet but must
have the same /etc/resolv.conf name server entries and a routing
entry with the DSL-connected computer as a gateway. For example, if the
host computer with the DSL connection has IP address 192.168.0.1, and other
computers on your LAN use addresses in the 192.168.0.XXX range, use the
route command on each computer like this:
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matthew@seymour:~$ sudo route add default gw 192.168.0.1
Note that you can also use a hostname instead if each computer has an
/etc/hosts file with hostname and IP address entries for your LAN. To
stop your connection, use the adsl-stop command:
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matthew@seymour:~$ sudo /sbin/adsl-stop