- A Word about Windows
- Let's Get Started
- The Firm
- Basic Networking
- Common Networking Services
- Summary
This chapter is from the book
This chapter is from the book
This chapter is from the book
Basic Networking
It is assumed that you are familiar with establishing network connectivity using either Linux or Windows NT/2000/XP. TCP/IP is the transport protocol in use everywhere. Because the Internet is based on TCP/IP, use of other protocols is declining and can be expected to disappear over time. Networked systems that use TCP/IP have a number of issues to address. For both Linux and Windows, the issues are the same. The first issue is registration and allocation of TCP/IP addresses. Internet domain name registrations can be done at http://www.networksolutions.com.
Our company will have a presence on the Internet. Therefore, it will register a name with Internic and request a block of IP addresses. There are three classes of Internet networks: Class A, Class B, and Class C. Class A networks can have up to 16 million addresses. Class B can have up to 65,000 addresses. Class C can have up to 256 addresses. In all cases each network has two reserved addresses. For instance, the Class A network 47.0.0.0 has the 47.0.0.0 address reserved for the name of the network. The 47.255.255.255 address is reserved as the broadcast address for the 47.0.0.0 network. Addresses are allocated per Table 1–4.
Table 1–4 Internet address classes
|
Network Class |
Addresses |
Comment |
|
Class A |
X.a.a.a |
16,777,216 – 2 addresses available |
|
Class B |
X.Y.a.a |
65,536 – 2 addresses available |
|
Class C |
X.Y.Z.a |
256 – 2 addresses available |
For the purposes of this book, we will use the domain name elsolutions.com.
Another possibility is to request a block of addresses from the Internet Service Provider (ISP) that will connect us to the Internet. This method has an advantage in that routing to the addresses granted us by the ISP is already in place. Addresses from the ISP are globally unique and are already present on the Internet and routed properly. If we acquire our addresses from http://www.networksolutions.com there is no guarantee that we can get our blocks of addresses routed. For instance, the closest ISP might not have bandwidth in their routers for another subnet.
Once a block of addresses has been obtained, we need to locate a "connection" to the Internet—an existing connection that we can attach to. Good candidates are local ISPs and local universities. There may be forms, fees, and ISP rules associated with this hook-up. We will refer to the "other end" of our connection as our ISP. The next issue is determining how we are going to actually communicate with this node. Often, a T1 connection is the most expedient. A T1 connection is supported by our local telephone company and provides point-to-point connectivity from our location to the node to which we have negotiated a connection. It is a dedicated connection, so no dialing is required.
At our end of the connection, we install and configure a TCP/IP node (Linux or Windows) and perform checkout testing until we can verify all basic networking services are functional. We will have to configure on our gateway machine our IP address, our DNS server, DNS server routing, and any routing planned for the site.
Our external IP addresses are assigned by Internic. For the gateway machine, we can choose any of the IP addresses we have been assigned. Once we choose it, we have to get our ISP to register it in its DNS zone file (the DNS database) and in its router database. That means we also have to choose a domain name and a machine name. We chose a domain name when we registered with Internic. Now we have to choose a machine name for our gateway machine. Since our machine will be located within our domain, we may name it anything. For instance, the following are all allowable names:
microsoft.elsolutions.com
ibm.elsolutions.com
compaq.elsolutions.com
We own all names to the left of elsolutions.com. We don't recommend using trademarked names of other companies; however, there are no restrictions on names in our domain name space. We chose the following as our gateway machine:
elgate.elsolutions.com
We now have a machine name, a domain name, and an IP address. We need our ISP to register us in its DNS database. We will be deploying our own Internet DNS server, so we need a minimum of four DNS records in the ISP DNS zone file, listed in Table 1–5.
Table 1–5 DNS records to be registered in ISP DNS zone file
|
Name |
Type |
Address |
|
elgate |
A |
InterNIC or ISP-assigned globally unique address |
|
elsolutions.com |
SOA |
elgate.elsolutions.com |
|
elgate.elsolutions.com |
NS |
elgate.elsolutions.com |
|
elsolutions.com |
MX |
elsmtp.elsolutions.com |
Your ISP will also (most likely) ask for the email address of the owner of this DNS zone. Here, the email address is the administrator's.
egb@elsolutions.com
Once the ISP link is set up and running, we should be able to ping most Internet sites. We should also be able to use our Internet browser on the gateway machine to browse the Internet. In fact, these are good tests of fully functional connectivity. We will talk more about DNS, DHCP, and testing network setups in Chapter 10, "Network Management." So far, there has been nothing specific to Linux or Windows.
At this point, we are ready to start configuring our site. We are still in basic networking setup mode. We need to configure a DNS server, routing for any subnets we deploy and any Simple Network Management Protocol (SNMP) clients needed. The last of the basic networking services are the firewalls. The existence of the firewalls will force all Internet-bound traffic to go through them. The inner firewall translates nonroutable internet addresses to one of our routable external addresses. The responses are reverse-translated. A request from our intranet appears as a request from the inner firewall from the point of view of a requested external service. The purpose is to maintain control over internal and external access—who inside our organization may access the Internet and who outside our organization may access our intranet. While controlling external access is often considered more important, internal access must also be controlled, since both may expose the company to security risks and computer viruses. Our network will consist of a number of servers connected both to the Internet and an intranet. We will choose 10.87.X.Y for our internal net. The 87 is chosen as a random number according to the recommendations in IETF Request for Comment (RFC) 1918. The complete collection of RFCs can all be found at ftp://ftp.rfc-editor.org/in-notes.
The servers requiring Internet connectivity will be allocated addresses from the pool of globally unique addresses acquired from Internic or our ISP. If our security needs or traffic demands increase, we can subdivide our 10.87.X.Y network into multiple segments with routers.
Actual setup and deployment of these services will be discussed in later chapters. At this point we have established the groundwork for adding more services for actually getting work done.