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Chapter 3
Planning Internet Connectivity
3-41
3. Power cycle the CSU/DSU for the T-1 providing Internet access.
4. Try to access the company Web site using a computer with a separate
dial-up
modem connection to the Internet.
5. Ask Mark to try to access a different site on the Internet.
6. Call a user on a different LAN from Mark, and ask if he can access the
Internet.
7. Ask Mark to repeat his actions and see if he still can’t access the
company Web
site.
8. Try to access the company Web site using a computer on the network with a
reg-
istered IP address.
9. Check the NAT router logs to see if they are functioning properly.
Chapter Summary
■
When creating an Internet access strategy for a network, the first step is
estimating
how much Internet bandwidth the network needs. The Internet bandwidth
needed by a network is based on the number of users and the types of
applica-
tions they run.
■
WAN technologies such as dial-up modems, ISDN, CATV, DSL, leased lines, and
frame relay provide varying amounts of bandwidth and operational
characteristics,
which you must evaluate before selecting one for an Internet connection.
■
ISPs can provide a variety of services to business clients in addition to
providing
simple Internet access. Part of the Internet access strategy is determining
which ser-
vices you should implement in-house and which you should obtain from the
ISP.
■
An Internet connection is a gateway that can work in both directions,
enabling
Internet users to access your private network as well as allowing your users
Inter-
net access. Security problems can also originate on the private network,
from
users who monopolize or abuse the Internet connection.
■
Most NAT implementations today use masquerading, a technique that maps
unreg-
istered IP addresses to a single registered IP address combined with a port
number.
■
Proxy server products have evolved to now include an array of firewall and
access
control features that provide comprehensive Internet security for a private
network.
■
The first step in troubleshooting an Internet connectivity problem is to
isolate its
location. Reproducing the fault on other computers can tell you whether the
prob-
lem is in the computer itself or in a component that affects other users as
well.
■
To determine if an Internet connection problem is caused by a name
resolution
failure, which could be the result of an incorrect DNS server address or a
malfunc-
tioning DNS server, try connecting to the Internet using an IP address
instead of a
DNS name.
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