Lesson 3: Installing Exchange Server 2003 in a Front-End and Back-End Configuration

Front-end and back-end server configurations were introduced in Chapter 3, where the basic concepts and benefits of the architecture were discussed. In this lesson, you will learn how to install and configure Exchange Server 2003 in a front-end and back-end configuration and how to use clustering to maximize the benefits of the front-end and back-end architecture.

After this lesson, you will be able to

• Configure Exchange Server 2003 as a front-end server

• Understand how to incorporate Network Load Balancing and the Cluster Service to create highly scalable and highly available Exchange Server 2003 organizations

Estimated lesson time: 45 minutes

Configuring Exchange Server 2003 as a Front-End Server

Both Exchange Server 2003, Standard Edition, and Exchange Server 2003, Enterprise Edition, support configuration as front-end servers, which do not host user mailbox and public folder stores. One of the primary benefits of using a front-end server is that it allows you to publish a single external server address to Internet-based clients, regardless of what physical back-end server actually hosts a particular mailbox or public folder replica. In addition, there is a security benefit of having a front-end server outside of a firewall that communicates with Internet-based client computers and communicates securely with the back-end servers. This prevents Internet-based traffic from communicating directly with Exchange Server 2003 servers that host user data.

There are a number of potential configuration changes to be made prior to configuring an Exchange Server 2003 server as a front-end server because front-end servers, by design, only relay traffic from the Internet to back-end servers on the internal network. First, the server cannot host a Recipient Update Service. If it does, you will have to delete or move the Recipient Update Service to another server using Exchange System Manager. Next, the Exchange Server 2003 server cannot host offline address lists. If it does, you must remove them from the server using Exchange System Manager. The Mailbox Management service, which starts and stops the mailbox cleanup agent, cannot be run on a front-end server either and must be removed. Finally, the free and busy service, which tracks the free and busy status of user calendars, does not run on front-end servers. Once you remove these services, you will be able to configure the server as a front-end server. In the practice at the end of this lesson, you will configure a front-end server.

There are several additional considerations when creating front-end servers.

• If the front-end server accepts SMTP mail from Internet-based clients, you must start the Microsoft Exchange Information Store service and mount at least one mailbox store. In certain situations, such as generating nondelivery reports, the SMTP service requires the store to perform a conversion. If a mailbox store is not mounted, messages that have to be converted are stuck in the local delivery queue. For security reasons, make sure that user mailboxes are not stored in the mailbox store of a front-end server. If there are servers that are running Exchange Server 5.5 in the same site or routing group, the Microsoft Exchange MTA Stacks service must run on the front-end server. By doing so, the MTAs can bind and transfer mail by using remote procedure call (RPC), which was the method of internal message transport in Exchange Server 5.5 (Exchange Server 2003 uses SMTP).

• If you must change the configuration by using Internet Services Manager, such as for changing the Secure Sockets Layer (SSL) configuration, leave the mailbox store intact on the front-end server.

• When you create a front-end server, do not delete the First Storage Group object in Exchange System Manager. The Microsoft Exchange Information Store service (and its related services) depends on the First Storage Group object.

If you are installing Exchange Server 2003 into an existing Exchange 2000 Server front-end and back-end configuration, you must first upgrade all the front-end servers and then upgrade the back-end servers.

As a general guideline, use one front-end server for every four back-end servers. However, this number is only a guideline; it is not a rule. Front-end servers do not need large or particularly fast disk storage, but they should have fast central processing units (CPUs) and a large amount of memory. There is no need to back up the disks on the front-end server unless you choose to enable SMTP. SMTP must be backed up because it writes queued mail to the local disk. For POP3, Internet Message Access Protocol 4 (IMAP4), and HTTP (OWA), no user data is stored on the drives of the front-end server.

Front-End and Back-End Servers and Clustering

The front-end and back-end architecture scales well with the use of Network Load Balancing and the Cluster Service. Since front-end servers do not host user data, they are more akin to Web servers than a typical Exchange Server configuration. As a result, front-end servers are well suited for using Network Load Balancing. In this type of configuration, you can scale up to 32 nodes in a cluster using Network Load Balancing, having the cluster service Internet-based clients connecting through OWA, POP3, or IMAP4. The cluster functions as a single entity to client requests and relays traffic back and forth between the client computer and the back-end server.

Back-end servers are better suited for the Cluster Service. A common highly scalable and highly available Exchange Server 2003 configuration is to create a cluster using Network Load Balancing, configure all the Exchange Server 2003 server nodes on the cluster as front-end servers, and have them connect to a back-end Exchange Server 2003 active/passive cluster running the Cluster Service.

When you have front-end servers, it is necessary to modify settings using both Cluster Administrator and Exchange System Manager. To configure a clustered back-end server using the Cluster Service, you must map each front-end server to all server nodes of the back-end Cluster Service cluster so that any node can accept proxy requests from any front-end server. Proxy requests are requests for messaging services from client computers running OWA, POP3, or IMAP4 that are sent to the back-end cluster through the front-end servers. All communication between front-end and back-end servers goes through TCP port 80, regardless of the port used for communication between the client computer and the front-end server.

Exchange Server 2003 uses the concept of virtual servers to refer to instances of IP services that it provides. By default, there are a number of different services that Exchange Server 2003 is configured with to support different types of messaging clients. For example, there are virtual servers for HTTP access to Exchange Server 2003, as well as for POP3, IMAP4, NNTP, and SMTP access. They are virtual servers because each service runs within the context of the Exchange Server 2003 server, not as truly separate servers. However, at the same time, each virtual server can be configured independently with its own IP address, security settings, and port numbers. But these IP virtual servers are not the same as a virtual server running on the Cluster Service. An HTTP virtual server on a Cluster Service cluster defines the resources that make an IP HTTP virtual server available through Exchange Server 2003 on a cluster.

There are a few steps to configure HTTP virtual server resources for an Exchange Server 2003 virtual server functioning as a back-end server. First, you must create the HTTP virtual servers in Exchange System Manager. Next, you must create virtual directories to match the directories configured on the front-end server. Finally, you must add new HTTP virtual server resources to the Exchange virtual server. However, you do not need to perform this configuration if you are only making the default HTTP virtual server available, servicing a single domain. The default configuration of Exchange Server 2003 and the Exchange Server 2003 virtual server already has the HTTP virtual server, virtual directory, and HTTP virtual server cluster resource configured. However, if you are supporting multiple domain names through HTTP, you must create separate HTTP virtual servers for each domain. For example, if Contoso, Ltd., acquires Fabrikam, Inc., and after merging, it is necessary for users to access mailboxes in both contoso.com and fabrikam.com. By default, there is an IP virtual server for contoso.com, but you will need to create an additional one for fabrikam.com. Creating virtual servers and virtual directories is the focus of Chapter 9.

Practice: Installing Exchange Server 2003 in a Front-End and Back-End Configuration

In this practice, you will configure Server02 in the tailspintoys.com domain as a front-end server, connecting to the Exch-VS01 back-end virtual server that you created earlier in this chapter. Before completing these exercises, you must complete the exercises in Lessons 1 and 2 of this chapter.

Exercise 1: Configure Exchange Server 2003 as a Front-end Server

1. Make sure that Server01 is online and that the Exchange Server 2003 virtual server Exch-VS01 is running. On Server02, install Exchange Server 2003 as a typical installation, which will have it join the Tailspintoys organization.

2. After installing Exchange Server 2003, reboot if prompted.

3. Start Exchange System Manager and expand the Recipients container. Click the Recipient Update Services container.

4. There should be two Recipient Update Services that reference Server02. Right-click the one that has (TAILSPINTOYS) in the name, and then click Delete. Rightclick the one that has (Enterprise Configuration) in the name, and then click Properties. Next to Windows Domain Controller, click Browse, and then enter Server01 for the name. This will move the Recipient Update Service off of Server02. Click OK, and then click OK again.

5. Click the Offline Address Lists container. You should have offline address lists for both Exch-VS01 and Server02. Right-click the Default Offline Address List for Server02, and then click Delete.

6. Expand the Servers container. Right-click Server02 and click Properties. Select the check box for This Is A Front-End Server, and click OK. You will see a warning message similar to Figure 6-13. Click OK to continue.

   
   Figure 6-13: Confirming the conversion to a front-end server

7. Restart all the Exchange Server services, as well as the World Wide Web Publishing Service.

In a simple front-end and back-end topology, no additional configuration is required on the front-end servers. However, if you are hosting multiple domains, you must configure virtual servers and virtual directories for each of the domains you will be hosting.

Lesson Review

The following questions are intended to reinforce key information presented in this lesson. If you are unable to answer a question, review the lesson materials and then try the question again. You can find answers to the questions in the "Questions and Answers" section at the end of this chapter.

1. You are the Exchange Server administrator for TailspinToys, which recently acquired WingtipToys. TailspinToys uses a front-end server outside of its firewall that connects to a back-end server cluster. You have migrated the mailboxes for WingtipToys employees onto the Exchange Server 2003 cluster. In order to support Internet-based client computers connecting to WingtipToys resources, you configure a new HTTP virtual server and virtual directory on the front-end server for wingtiptoys.com and mimic it on the Exchange Server 2003 virtual server. However, mail traffic fails to flow properly, even though it works fine for TailspinToys. You verify the network settings, and they are all correct. What else might you be missing?

2. You install Exchange Server 2003 clean onto a new server, with the plan to make it a front-end server in an existing Exchange Server 2003 organization. After a successful installation, you start Exchange System Manager and expand the Servers container, then right-click the server and then click Properties. You select the check box for This Is A Front-End Server and click OK, but you receive an error. What did you do wrong?

3. You are the Exchange Server administrator for an organization that has an existing Exchange 2000 Server front-end and back-end server architecture. There are four non-load-balanced front-end servers servicing 15 non-clustered back-end servers. You want to upgrade to Exchange Server 2003 on all servers. In what order would you upgrade?

   1. Upgrade a front-end server and then each of its corresponding back-end servers, and then repeat the process with the next front-end server.

   2. Upgrade all the back-end servers, and then upgrade all the front-end servers.

   3. Upgrade back-end servers, then upgrade the corresponding front-end server, and then repeat the process with the next set of back-end servers.

   4. Upgrade all the front-end servers, and then upgrade all the back-end servers.

Lesson Summary

• Front-end servers work best with Network Load Balancing, and back-end servers work best with the Cluster Service.

• A general guideline is to use one front-end server for every four back-end servers.

• Recipient Update Services, Offline Address Lists, the Mailbox Management service, and the free and busy service are not supported on front-end servers.

• Front-end servers should have a mailbox store defined but should not host user mailboxes.

• You must duplicate the virtual server and virtual directory configuration between the front-end and back-end servers.