programming4us
programming4us
ENTERPRISE

Exchange Server 2010 : Utilize the Availability Options for Servers Based on Role (part 3) - Implement Redundant Transport Servers

- How To Install Windows Server 2012 On VirtualBox
- How To Bypass Torrent Connection Blocking By Your ISP
- How To Install Actual Facebook App On Kindle Fire

3. Implement Redundant Transport Servers

When implementing redundancy for Transport servers, it's important to consider each job that the server performs. Here are the primary components of Transport servers that you will want to make redundant:

  • Internal message routing

  • External message processing

3.1. Implement Redundancy for Internal Message Routing

When a user sends a message in Exchange, the message is submitted by the Mailbox server to a Hub Transport server that is in the same Active Directory site. The Hub Transport server is then responsible for sending that message to another Transport server that is considered to be the next hop in order for the message to reach its destination. So when considering redundancy for internal message routing, you need to ensure that you have redundant Transport servers for Mailbox servers to submit mail to. You also need to ensure that you have redundant servers to receive the messages that are sent from site to site by the Hub Transport servers that are routing the messages inside Exchange.

The need for this level of redundancy is evident when you look at the example routing topology in Figure 7.

Figure 7. Why multiple transport servers are preferred

The Baltimore site only has one Hub Transport server. If a message is sent from a user in Seattle to a user in Baltimore and if the Baltimore Hub Transport server is offline, the message will remain queued at one of the Seattle Hub Transport servers. However, if a user in Baltimore sends a message to a user in Seattle and one of the Hub Transport servers in Seattle goes down, the message will be sent to the other Hub Transport server that is still functioning. Users in Seattle can still send and receive email until the problem is resolved and the second Hub Transport server is brought back online. Leaving only one Hub Transport server in an Active Directory site introduces a single point of failure for mail routing to that site.

Accomplishing this level of redundancy for internal message routing is easy. You simply install multiple Hub Transport servers in each Active Directory site that contains Mailbox servers. No special configuration is necessary to have internal message routing redundancy.

3.2. Implement Redundancy for External Message Routing

Ensuring that external message routing is redundant requires a little more work than internal routing redundancy. Whether you are using Hub Transport servers for external messages or Edge Transport servers, implementing redundancy is the same. There are two facets to consider:

  • Redundancy for sending mail outside the organization

  • Redundancy for receiving mail directly from the Internet

3.2.1. Add Redundancy for Sending External Messages

To send mail outside an organization, you need to have a send connector configured. The send connector determines how mail destined for different email domains is processed. Each send connector has a list of source servers, which are the Transport servers that can be used to send mail for the email domain name specified on the send connector. If there is only one Transport server defined on a send connector and the Transport server goes offline, messages destined to that domain namespace will not be sent. Therefore, it's important to use multiple Transport servers in a send connector.

To add Transport servers to an existing send connector, use the following steps:

  1. Open the EMC and browse to the Organization Configuration => Hub Transport node in the Console tree.

  2. Click the Send Connectors tab in the Work area.

    The configured send connectors for the Exchange organization are displayed in the list.

  3. Select the send connector that you want to add redundant Transport servers to. Click the Properties task in the Actions pane on the right.

  4. In the properties dialog box for the send connector, click the Source Server tab.

    The current Transport servers configured to send mail for the connector are listed on this tab.

  5. Click the Add button to add an additional Transport server.

  6. In the search dialog box that appears, select the Transport server that you want to add and click OK.

    Add any additional Transport servers that you want to include by repeating this step.

  7. When back in the properties dialog box, click OK to makes the changes and close the dialog box.

3.2.2. Add Redundancy for Receiving Internet Mail

When a Transport server is Internet facing, the Mail Exchanger (MX) records for the domain's DNS name are configured to point Internet mail servers to the Transport server. For example, if joe@contoso.com is receiving a message from tim@fabrikam.com over the Internet, the fabrikam.com Mail server queries the contoso.com DNS domain for MX records to determine which server should receive the incoming message. Therefore, it's important to ensure that there are multiple servers that can receive mail based on that MX record lookup.

There are two methods for making MX records redundant:

  • Create more than one MX record for a DNS domain. Point each MX record to an Internet-facing Transport server.

  • Create a single MX record, but point it to multiple host records. Each host record maps to the IP address of the Transport servers that are Internet-facing.

When the first approach is used, a DNS query returns all the MX records. It is then up to the mail system that is sending the message to select the MX record to use according to its internal algorithm. There is no guarantee that a different server will be used each time, as the external server gets to choose what to use.

However, with the second approach, only a single MX record is returned. This MX record is the host record that uses multiple IPs. When the sending server receives the MX record, it performs a host record lookup and receives the list of IP addresses behind that host record. The order of the IP list is controlled by the DNS server, which uses a round-robin ordering or a random ordering. The sending server chooses the first IP address in the list and sends the message to that IP address. This method puts the control in the hands of the DNS server and not the email system. Figure 8 and Figure 9 show how the DNS response is different in these two methods.

Figure 8. The DNS response when using multiple MX records

Figure 9. The DNS response when using multiple host records

In addition to configuring multiple MX records, you will want to ensure that you have a receive connector on each of your Internet-facing Transport servers. The receive connector allows the Transport server to listen for incoming mail on the port that is configured. Edge Transport servers configure receive connectors to receive Internet email automatically when the Edge role is installed. However, if you have Internet-facing Hub Transport servers, you need to modify the permissions on the default receive connector on each Hub Transport server that is Internet-facing so that it can receive messages from the Internet.

Other  
  •  Exchange Server 2010 : Track Exchange Performance (part 2) - Test the Performance Limitations in a Lab
  •  Exchange Server 2010 : Track Exchange Performance (part 1) - Use the Performance Tools Available
  •  Exchange Server 2010 : Keep Exchange Healthy (part 2) - Verify Exchange Server Health
  •  Exchange Server 2010 : Keep Exchange Healthy (part 1) - Ensure That Mail Flows Freely
  •  Programming WCF Services : Queued Services - Instance Management
  •  Programming WCF Services : Queued Services - Transactions
  •  Exchange Server 2010 : Implementing Client Access and Hub Transport Servers - Test Cmdlets for CAS and Hub Transport Servers
  •  Exchange Server 2010 : Implementing Client Access and Hub Transport Servers - Installing the Hub Transport Server
  •  Exchange Server 2010 : Implementing Client Access and Hub Transport Servers - Transport Pipeline
  •  Exchange Server 2010 : Implementing Client Access and Hub Transport Servers - Understanding the Hub Transport Server
  •  
    Top 10
    - Microsoft Visio 2013 : Adding Structure to Your Diagrams - Finding containers and lists in Visio (part 2) - Wireframes,Legends
    - Microsoft Visio 2013 : Adding Structure to Your Diagrams - Finding containers and lists in Visio (part 1) - Swimlanes
    - Microsoft Visio 2013 : Adding Structure to Your Diagrams - Formatting and sizing lists
    - Microsoft Visio 2013 : Adding Structure to Your Diagrams - Adding shapes to lists
    - Microsoft Visio 2013 : Adding Structure to Your Diagrams - Sizing containers
    - Microsoft Access 2010 : Control Properties and Why to Use Them (part 3) - The Other Properties of a Control
    - Microsoft Access 2010 : Control Properties and Why to Use Them (part 2) - The Data Properties of a Control
    - Microsoft Access 2010 : Control Properties and Why to Use Them (part 1) - The Format Properties of a Control
    - Microsoft Access 2010 : Form Properties and Why Should You Use Them - Working with the Properties Window
    - Microsoft Visio 2013 : Using the Organization Chart Wizard with new data
    REVIEW
    - First look: Apple Watch

    - 3 Tips for Maintaining Your Cell Phone Battery (part 1)

    - 3 Tips for Maintaining Your Cell Phone Battery (part 2)
    programming4us programming4us
    Celebrity Style, Fashion Trends, Beauty and Makeup Tips.
    programming4us
     
     
    programming4us