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Barracuda Load Balancer ADC

Microsoft Exchange Server 2013 and 2016 Deployment

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Barracuda Networks has conducted interoperability tests using the Barracuda Load Balancer ADC and Microsoft® Exchange Server 2013 and Microsoft Exchange Server 2016. Follow the steps in this guide to deploy the Barracuda Load Balancer ADC to increase the scalability and reliability of your Microsoft Exchange Server deployment. Using a Barracuda Load Balancer ADC allows load balancing of a Client Access Server (CAS).

Product Versions and Prerequisites

You must have:

  • Barracuda Load Balancer ADC version 5.1 or above.
  • Microsoft Exchange Server 2013 or Microsoft Exchange Server 2016.
  • Installed your Barracuda Load Balancer ADC(s), connected to the web interface, and activated your subscription(s). 
  • If you want to deploy the Microsoft Exchange Server with high availability, clustered your Barracuda Load Balancer ADCs . For more information, see High Availability.


Microsoft Exchange Server 

A Microsoft Exchange Server deployment consists of Client Access Servers (CAS) and Exchange Mailbox servers. 

Fully Qualified Domain Name (FQDN)

The unique name for a specific computer or host that can resolve to an IP address (e.g.,
Virtual IP (VIP) AddressThe IP address assigned to a service. Clients use the virtual IP address to connect to the load-balanced service.
ServiceA combination of a virtual IP address and one or more TCP/UDP ports that the Barracuda Load Balancer ADC listens on. Traffic arriving on the specified port(s) is directed to one of the real servers associated with a service.
Instant SSL

Instant SSL provides SSL (HTTPS) access to content on servers without having to modify the servers or the content on the servers. The Barracuda Load Balancer ADC rewrites the "http" links in the response to "https".

Client Access Server (CAS)Client Access Server supports various protocols used by end users to access their mailboxes. This includes services such as RPC Client Access, IMAP, POP3, OWA, and ActiveSync.
Real ServerA server associated with a service that handles the requests forwarded to it by the Barracuda Load Balancer ADC.
Outlook Web App (OWA)Originally called Outlook Web Access, OWA is the Webmail component of Microsoft Exchange Server 2010.

Deployment Topology for Microsoft Exchange Server 2013


Deployment Topology for Microsoft Exchange Server 2016


Deploying Exchange Services on the Barracuda Load Balancer ADC

Configuring Clustered Barracuda Load Balancer ADCs

If your Barracuda Load Balancer ADCs are clustered, the configuration between the active and passive units is synchronized; you only need to configure the active Barracuda Load Balancer ADC.

To deploy the Exchange servers with the Barracuda Load Balancer ADC, complete the following steps:


Barracuda Networks recommends that you use the same certificate on the Barracuda Load Balancer ADC and each CAS.

Step 1. Create the Exchange Services
  1. Log into the Barracuda Load Balancer ADC as the administrator.
  2. Go to the BASIC > Certificates page, and create or upload a certificate for the service.
  3. Go to the  BASIC > Services page and add the following services. Click Add Service and enter the values in the corresponding fields (each service must be added separately).



    IP Address

     PortHTTP Service PortSession Timeout

    SSL Settings


    Load Balancing


    Instant SSL

    VIP address for the FQDN
    that clients use to access
    the Outlook Web Access
    (OWA) and Exchange
    Admin Center.


    Secure Site Domain – Enter the
    domain name of your Exchange
    server. If the internal and external
    domain are different, you can
    use wildcard characters.
    For example: *

    If your Barracuda Load Balancer
    ADC is running version 5.1.1 and
    , set the Rewrite Support
    option to Off. For versions below
    , this option is named Instant SSL.

    Select the certificate that you uploaded for the service.

    Persistence Type: Cookie Insert

    Persistence Time (Barracuda
    Load Balancer ADC 5.4 and earlier)
    : 1200 seconds

    Cookie Expiry (Barracuda
    Load Balancer ADC 6.0
    and later)
    : 1200 seconds

    Cookie Name
     Choose  a cookie name.

    Exchange_SMTPTCP ProxyVIP address for the FQDN
    that Microsoft Exchange
    server uses to receive mail.

    Persistence Type: Source IP

    Persistence Time: 1200

  4. Click Create.

  5. If you have the Barracuda Load Balancer ADC 540 and above, you can enable Application Security for the service.
    1. For Application Security, select Enable.
    2. For Security Mode, select the Passive mode. It is recommended that you run the service in Passive mode before going active. 
    3. From the Security Policy list, select owa2013. This policy is predefined for all Exchange applications and applies to both Exchange Server 2013 and 2016.

    4. You need to modify the default owa2013 policy. Go to the SECURITY > Security Policies page and select the owa2013 security policy. In the Cookie Security section, set Tamper Proof Mode to None.

      If you want to use Integrated Windows Authentication with the Exchange_InstantSSL service, go to the Request Limits section of the security policy settings and increase the Max Header Value Length to 800.

Step 2. Add the Real Servers

Add each CAS to your service. For each server, enable SSL and configure health checks. Certificate validation can be ignored.

  1. On the BASIC > Services page, verify that the correct service for the server is displayed.
  2. Click Add Server. Enter the values in the corresponding fields.

    IP AddressPortServer Monitor
    IP address of the CAS443
    • Testing Method: Simple HTTPS
    • Port: 443
    • Test Target: /owa/auth/logon.aspx (unless you modified the default path of logon.aspx)
    • Test Match: Microsoft Corporation
    • Additional Headers: User-Agent: Barracuda Load Balancer ADC Server Monitor
    • Status Code: 200
    • Test Delay: 30
  3. Click Create.
  4. If SNI is enforced on the Microsoft Exchange server(s), click Edit for each affected server, expand Settings and set Enable SNI to Yes.

Step 3. Configure an HTTP Request Rewrite Rule

To simplify access to the Outlook Web Access site for your users, configure a rewrite rule to add /OWA to the end of the URL.

  1. Go to the TRAFFIC > Web Translations page.
  2. From the Service list, select the Exchange_InstantSSL service.
  3. In the HTTP Request Rewrite section, add the following rule. Click Add Rule and enter the values in the corresponding fields.

    Rule NameSequence number ActionOld ValueRewrite ValueRewrite Condition
    OWA3Redirect URL //OWA*
  4. Click Save.
Step 4. Configure DNS

Configure the VIP address on the CAS virtual directories. Configure the DNS for the following domain names to point to the VIP address that you created for the Exchange_InstantSSL service:

  • mail.domain.local
  • autodiscover.domain.local
  • eas.domain.local
  • outlook.domain.local
  • oab.domain.local
  • ecp.domain.local

Configure HTTPS namespace on the Exchange Admin Center:

  1. Log into your Microsoft Exchange Admin Center.
  2. Click Servers > Virtual Directories.
  3. Select CAS1, click Edit , and configure external access domain.
  4. Add both servers to the list and configure the external domain.
  5. Click Save.

Next Step

You can configure authentication and access control for your applications. For more information, see Access Control.


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