Chapter 3

Planning Internet Connectivity

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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

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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.