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Citrix/Metaframe Load Balancing

Posted on 2000-03-27
Medium Priority
Last Modified: 2013-12-28
We have load balancing installed on two Citrix/Metaframe servers.  However, after we scheduled reboots 1 hour apart each morning (2 and 3 am) via the AT command, automatic load balancing "broke."  In order to get load balance going, we must log into the non-Citrix browser server and start load balancing manually.  From what I can see Citrix support documents on load balancing problems only deal with router and firewall issues, but that is not the problem with our Citrix servers because they are on the same LAN and are not separated by routers/firewalls.  Running lbadmin from the command prompt or GUI interface works fine, but it fails to find the Citrix master brower when run via the AT command.  The failure occurs even when a domain admin is logged on.  Via the AT command, lbadmin searches for the Citrix Master browser but can't find it.  I've struggled with the problem for a couple months and many knowledgeable people have been unable to find a solution.  Any help would be greatly appreciated!  Thank you.

PS  Please respond to julie@wesche.com.
Question by:jmw1000
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Expert Comment

ID: 2662373
Here's some Citrix information that relates to your problem. I'm posting it because in your question you mentioned only finding solutions relating to routers/firewalls.

My advice here is that your network is to have only one protocol. If using tcp/ip, all member servers have static addresses.

Use an LMhosts file pointing to each machine and nominate the first machine to reboot as the main controller.
As each each machine reboots, it will refer to this machine.

Your citrix licensing is spread across machines.

Take into account that the default timeout for a Citrix master browser list rebuild is 30 mins by default.

Here's the huge file. Sorry i had to post it here as i don't have a direct url.

ICA Browsing and Error Handling Overview

ICA browsing is at the heart of WinFrame license pooling, load balancing, and application publishing.

A separate ICA browsing system is in operation for each network protocol (TCP/IP, IPX/SPX, or NetBIOS) supported by WinFrame servers on a subnetwork. Each ICA browsing system is independent of the other systems. If a WinFrame server supports a network protocol, it can support license pooling; you must configure network WinStations for that network protocol to support user logons and published applications on that server.

For example, if two of the three servers in a subnetwork support IPX/SPX and all three servers in the subnetwork support TCP/IP, and each server has 15 licenses (all of which are pooled), 45 pooled licenses are available for TCP/IP connections but only 30 pooled licenses are available for IPX/SPX connections. If TCP/IP WinStations are configured on only two of the three servers, only those two servers can support TCP/IP user logons or published applications, up to a total of 45 users. The total number of users includes all connection types; for instance, with all 45 licenses in use, you might have 30 TCP/IP users, ten IPX/SPX users, and five Dial-in users on at one time, and 20 TCP/IP users, 15 IPX/SPX users, and ten Dial-in users on at another time.

ICA Browsing System Description

The ICA browsing system contains two categories of servers:

 The Master Browser. The Master Browser is a server that is selected by an election process (called Master Browser Election) to contain the master list of available Citrix servers, published applications, and pooled licenses. At any time, there is only one master browser per protocol (TCP/IP, IPX/SPX, or NetBIOS) per subnet. If several protocols are supported on a subnet, the master browsers for each protocol can be different computers. License pooling is not supported across subnets; however, ICA browsing can be configured to allow Citrix server logons, load balancing, and published applications access across subnets.

 Member Servers. Member Servers are the other WinFrame servers on the network that have not been elected as the master browser. Member servers periodically report information about their available connections, published applications, and pooled licenses to the master browser. If a network protocol is not configured on a server, that server is not a member server of the ICA browsing system for that protocol. Citrix server logon access is controlled by WinStation Configuration; the number of concurrent users for a connection type is limited by the number of configured WinStations as well as free licenses.

The master browser collects and maintains information from member servers in a database on the master browser for use by the Citrix ICA Clients for locating servers and published applications, by license management support, and by application publishing support. The master browser does not initiate contact with the member servers but merely collects information provided by the member servers.

Each member server reports its server data to the master browser periodically (the default interval is every 30 minutes) or whenever a change occurs, such as a user logging on or off at a client or an administrator adding a new published application or changing the pooled license count.

The master browser retains the information reported by a server in its database for up to 30 minutes, with the exception of license information, which is retained for 48 hours.

Whenever there is a browser election and a new master browser is elected, the server information database on the new master browser starts out empty and all information from the database on the previous master browser is lost. Each member server automatically updates the new master browser within a few seconds after the election.

If a member server goes down or off-line, its pooled licenses time out after 48 hours or at the next master browser election, whichever comes first. Member server information used for server browsing or application publishing times out after 30 minutes or at the next master browser election, whichever comes first.

Master Browser Elections

Master browser elections can be initiated by a client (WinFrame PC Client, Citrix ICA Client, or ICA device such as a Wyse Winterm) by a member server or by a master browser. Master browser elections are usually caused by the master browser going down or off-line. Whenever there is a browser election and a new master browser is elected, the server information database on the new master browser starts out empty and all information from the database on the previous master browser is lost. Each member server automatically updates the new master browser within a few seconds after the election.

A client will initiate a master browser election if it does not receive a response from the master browser to a request such as a request for the server or published application list or a request to map a server name to a network address.

A member server will initiate a master browser election if it does not receive an acknowledgement from the master browser after sending information to the master browser or requesting information from the master browser.

A master browser will initiate a master browser election if it detects the presence of another master browser on the network (this is rare).

Handling Fault Conditions

In most cases, a single server (which can be the master browser or a member server) fails or is brought off-line for maintenance. In this case, the 30 minute timeout for application publishing and server enumeration ensures that momentary interruptions (such as a quick reboot after a system crash) have a minimal impact on the overall system. Because many installations depend on license pooling to support large numbers of users with server farms, the pooled license timeout has been made longer (48 hours) to avoid impacting system throughput if a server needs to be replaced or requires more extensive maintenance. However, if the master browser goes down or off-line, the next user logon or logoff will force a master browser election, causing the licenses associated with the downed server to disappear.

Because licenses are only used to validate logons, active user sessions are not terminated if the license count on the network goes below the number of currently logged on users; however, new users will not be able to log in until the number of active user connections goes below the number of available licenses, freeing up licenses.

Citrix does not recommend placing all the pooled licenses on a single server. Although it is unlikely that a master browser election would occur while the server containing the pooled licenses is down, if it does occur, all those licenses would be lost until that server comes on-line again.

Expert Comment

ID: 2662406
I'm reasonably ignorant with Metaframe issues, but I have a small suggestion.

Does your Messenger service start with administrator privileges?

In the services control panel, you can check this.

Hope my answer isnt too simplistic (especially after netmage's), but it's worth a shot to check that out.

Good luck,


Expert Comment

ID: 2679013
jmw1000, Hows the cure for this problem proceeding?


Expert Comment

ID: 2701129
Assuming that both your servers are in the same farm, enable on of the servers to try and be the master browser all the time and the other to be browser none of time.  Try not to make your Citrix servers PDCs or BDCs either.  Also make sure that each user logging into the farm carries the same load weight.  Then try logging in about 4 users and see if they spread out on the 2 servers.  Hope it helps.

Accepted Solution

netmage earned 4000 total points
ID: 2720820
Posting this comment as answer looking to get response from jmw1000.

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