Error 500, Internal Server Error -Message: Maximum number of concurrent connections exceeded. Please

[Dave Kissoondoyal]

We are running three web sites in a clustered environment on
WLBS. Afinity is none on UNICAST. Each server has two NICs. On the NIC with
Network Load Balancing, the SAME Virtual IP address is used for all three of
them. Each has a UNIQUE IP address on the same subnet.
WLBS tends to work fine since on the Event Viewer we can see that the 1st
WEB SERVER joins the cluster with the three Unique hosts ID and the 1st One
is the default web server.

The web servers are connected to a Database Server running MS SQL server
enterprise edition licensed as per CPU license. The Windows 2000 Advanced
Server Licensing mode on all the servers is per SEAT license.

Our customers are accessing our web servers and after some time getting
error 500, Maximum concurrent users have reached.

After monitoring the maximum number of Concurrent Connections, we notice the
following:

Web Server 1 (default) only 40 connections
Web Server 2 160 connections
Web Server 3 160 Connections

We have been told by our software provider that the connection problem lies
with the ADO components while communicating with the SQL server.

We have been turning round and round, without any luck.

Your help will be highly appreciated.

Thanks and best regards

Dave

 

[Curtis Koenig [MSFT]]

Hi Dave,
Lets clarify a couple of terms so we can all get on the same page. In NLB
you have three choices for affinity; none, single and class C. No affinity
means each request from a client can go to any NLB server, single means
once a session is established with a server all subsequent packets meeting
the rules go back to the same server and class C means all clients from a
given class C subnet go to the same server (this one is rarely used). NLB
can operate in 2 network modes; unicast and multicast. The recommendation
for multicast is that it must be used in a single NIC NLB configuration or
when a load balanced application calls for it, in general multicast is
never recommended as there are a great number of issues surrounding its
use. As such unicast is the most common mode and is what should be used for
2 network card configurations like yours.

Given the setup with 2 network cards you will want to confirm that the
setup is inline with this KB article for 2 network card configurations
(256910 IP Address Assignment for NLB with Multiple Network Adapters
http://support.microsoft.com/?id=256910). Essentially you have to have 2
different and distinct subnets, this is especially true when connecting to
a backend DB from the NLB balanced web site. You will want to have the your
Dedicated IP (DIP) and Virtual IP (VIP) in the same subnet and the backend
or ADMIN NIC in the separate subnet. In the case of a database connection
you also want to have the database in the same subnet as the ADMIN and not
the VIP/DIP.

So that covers the configuration details, the error message you are getting
could be coming from SQL I can not say for sure as my personal knowledge of
SQL is quite limited. However, if you configuration is correct and matches
the best practices I have described above what we should probably look at
next is a wlbs display output from one of the nodes to verify the setup and
maybe take a look at how the database is being used.

--
Curtis Koenig
Support Professional
Microsoft Clustering Technologies Support

Microsoft Certified Systems Engineer
Microsoft Certified Systems Engineer - Security

This posting is provided "AS IS" with no warranties and confers no rights.
Please reply to the newsgroup so that others may benefit. Thanks!

--------------------

From: "Dave Kissoondoyal" <[email protected]>
Subject: Error 500, Internal Server Error -Message: Maximum number of

concurrent connections exceeded. Please try again later