Most Common Interview Questions and Answers on Citrix Technologies

Most Common Interview Questions and Answers on Citrix Technologies including XenApp, XenDesktop, Provisioning Services and NetScaler, etc.,

This is an attempt to make a list of typical questions you can expect in the initial technical round for Citrix Administrator, Engineer, L1, L2, L3 and SME positions.  Apparently most people can answer these questions just by preparation but it makes to the interviewer about how strong the candidate in basic overview.

What is Delivery Controller?

  • Delivery Controller is the Core component of XenDesktop v5 & above, using  FMA. 
  • It is the server that centrally manages the XenDesktop site.
  • At least one delivery controller is installed on a site.
  • The delivery controller communicates with the database
  • It runs several services that manages
  • the hypervisor resources,
  • the user authentication and authorization/access,
  • the broker between the user requests and their virtual desktops and applications,
  • monitoring, and
  • the power management (shutting down of virtual desktops when needed), and so on.
  • It includes the functionality of Data Collector and Desktop Delivery Controller (DDC) roles that existed in previous XenDesktop versions up-to v4 that uses IMA. 
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    What is the impact to end users if Delivery Controller (FMA) is unavailable?

    • If none of the Delivery Controller Servers are available in a Site, VDA’s fails to register themselves with Delivery Controllers and thus will be unavailable for new session launches.  Thus users cannot access their applications or desktops.  However, the sessions that are already connected will continue to work. 
    • If just one of the Delivery Controller is unavailable, then VDA’s instantly (15-90 seconds) auto load-balances to other available Delivery Controllers in the Site.
    • If specific service on Delivery Controller is unavailable then its respective resources will become in accessible for users.  If Delivery Controller is unavailable 

    What is Data Collector?

    • Data Collector is the component of IMA used in XenDesktop up to v4. It is a Zone level role.
    • By default, in a XenDesktop farm, the initial Desktop Delivery Controller (DDC) installed is the farm master acts as the Data Collector, performing desktop resolution operations during starting the desktop and managing the hosting infrastructure.
    • Data collector exists as an in-memory database that maintains dynamic information about the servers in the zone, such as server loads, session status, published applications, users connected, and license usage
    • Data collectors receive incremental data updates and queries from servers within their zone. Data collectors relay information to all other data collectors in the farm
    • The data collector communicates information to the data store on behalf of the other servers in the farm
    • They act as communication gateways between zones in server farms that have more than one zone.

    What is the impact to end users if Data Collector (IMA) is unavailable?

    • Data Collector is Zone level role. If Data Collector is unavailable, a new data collector is automatically elected for the zone based on a simple ranking of servers (indicated by server’s election preference setting) in the zone.
    • The Data Collector election process is almost instant, automatic (without administrative interference) and is not dependent on the data store thus existing as well as incoming user sessions are unaffected by the election process.

    What are differences between StoreFront (SF) and Web Interface (WI)?

    StoreFront validates the user credentials with the help of the Active Directory domain controller which wasn’t the case with WI.  StoreFront will check the application subscription data store for the existing user subscriptions and then store those in the memory.

     

    What are the ICA and Session Reliability ports?

    • The Independent Computing Architecture (.ICA) uses TCP 1494 port.  ICA was initially defined for Intelligent Console Architecture.
    • The Session Reliability/Citrix Gateway Protocol (CGP) uses TCP 2598 port.

    What is Connection Leasing?

    Connection Leasing is a XenDesktop built-in capability, which lets users connect or reconnect to their most recently used applications and desktops, even when the site database is unavailable. However, this doesn’t help new or first time user scenarios.  With Connection Leasing enabled each DDC, or Controller, caches the users connections to his or her recently used applications and or desktops. By default connections are cached for a period of two weeks.

      

     

     

    Reference:

    Mastering Citrix XenDesktop by Govardhan Gunnala

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