Newsgroup: it.comp.os.win.win2000
Titolo: Microsoft WLBS

Buongiorno a tutto il NG,
ho un problema con delle macchine che implementano Microsoft WLBS, non
riescono a creare il cluster;
lo switch a cui sono attestate è un Cisco 6500. I server in questione
sono visibili tramite i rispettivi Ip ma non va' il virtuale,
non riesco a vedere neanche il MAC address.
Avete notizia di qualche settaggio particolare da applicare allo switch
??.
Grazie per le eventuali risposte.
Cordialità
Joe
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WLBS Cluster Is Unreachable from Outside Networks (Q197862)
Configuration Options for WLBS Hosts Connected to a Layer 2 Switches 
(Q193602)
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MS Windows Load Balancing Server: Issues with Switching and Routing
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Contents 
Introduction
Problem Description
Solution
Related Information
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Introduction
This document addresses a problem where Windows Load Balancing Server 
(WLBS) causes slow traffic through switches. 
WLBS on Windows NT and Windows 2000 allows servers to load balance 
traffic between groups (clusters) of servers. WLBS operates by sharing a 
virtual IP address so that all servers see all traffic destined for the 
cluster?s IP address. In certain configurations, WLBS can cause large 
quantities of unicast floods on a switch. This is not a switch problem 
but expected behavior. 
Problem Description
This problem appeared as a customer was monitoring traffic because there 
was a slow response across a specific switch. The customer saw unicast 
packets appearing on a Switched Port Analyzer (SPAN) port, where they 
should not appear. (A SPAN is a feature of the Catalyst 5000 switch that 
extends the monitoring abilities of existing network analyzers into a 
switched Ethernet environment. SPAN mirrors the traffic at one switched 
segment onto a predefined SPAN port. A network analyzer attached to the 
SPAN port can monitor traffic from any of the other Catalyst switched 
ports.) The unicast frames contained source addresses of the WLBSs 
A unicast frame is destined to one unique host so the SPAN port 
shouldn't see it, except in the situation of a flood. In the case of a 
flood, the switch will know the MAC address of the destination host 
after the first frame requesting this information comes back from the 
destination. The host on the particular port the customer in this 
situation was examining was not the destination for these frames. There 
are several ways this problem could manifest itself: 
Slow response on a given switch 
Slow response on a given switch on a given virtual LAN (VLAN) 
If the flooding gets bad enough, it could conceivably cause spanning 
tree problems if the switch loses Bridge Protocol Data Units (BPDUs) 
from other switches. 
There are several ways an NT administrator can choose to configure WLBS. 
The implications of these choices need to be understood because 
configuring WLBS can impact an internetwork in negative ways. Once the 
WLBS configuration options are configured properly, per the Microsoft 
recommendation, problems that match the problems in this document should 
no longer be present on a switch. 
Solution 
See the following link for configuration details: 
http://support.microsoft.com/support/kb/articles/Q193/6/02.ASP
?
LNG=ENG&SA=TE   
Or you can go to Microsoft?s support site and search for article 
Q193602, which is titled ?Configuration Options for WLBS Hosts Connected 
to a Layer 2 Switches.? 
There are also layer three implications with regards to Address 
Resolution Protocol (ARP). See 
http://support.microsoft.com/support/kb/articles/Q197/8/62.ASP
 
or search for article Q197862, which is titled ?WLBS Cluster Is 
Unreachable from Outside Networks? at Microsoft?s web site. 



Se per caso hai abilitato il multicast su WLBS dovresti toglierlo.
Quindi dovresti usare 2 schede di rete per ciascuna macchina, una
dedicata al "dialogo" interno tra i servers ed una dedicata al vero e
proprio balancing.
Alessandro
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Alessandro Borille
Microsoft MVP - (Windows 2000)