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What should you configure?

HOTSPOT
Your network contains an Active Directory domain named contoso.com. The domain contains two
member servers named Server1 and Server2. All servers run Windows Server 2012 R2.
Server1 and Server2 have the Network Load Balancing (NLB) feature installed. The servers are
configured as nodes in an NLB cluster named Cluster1. Both servers connect to the same switch.
Cluster1 hosts a secure web Application named WebApp1. WebApp1 saves user state information in
a central database.
You need to ensure that the connections to WebApp1 are distributed evenly between the nodes.
The solution must minimize port flooding.
What should you configure? To answer, configure the appropriate affinity and the appropriate mode
for Cluster1 in the answer area.

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Answer:

Explanation:
The Affinity parameter is applicable only for the Multiple hosts filtering mode.
/ The Single option specifies that NLB should direct multiple requests from the same client IP address
to the same cluster host.

Network Load Balancing Manager Properties
https://technet.microsoft.com/en-us/library/cc771709.aspx

9 Comments on “What should you configure?

  1. Blazz says:

    If the session state is being stored in a central database (i.e. SharePoint web front ends), why would you need to set the affinity to single? The could make one call to server 1 and the next call to server 2 and the state would be preserved because it’s stored in the SQL database.




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    1. mist74 says:

      It is clear that Affinity should be NONE: no one told us that the session state should be preserved on the same machine, even more, they told us that SQL DB is preserving it and WebApp is able to use it. But (!), none IS NOT PRESEN so the single is the most natural option if demanding EQUAL load balance. By the way: there is no CLIENT affinity option on real server console (evil M$, very tricky), and class C option bounds whole class C network to one server what potentially CAN cause more unbalanced environment.
      The second part is answered WRONG. Because MULTICAST always do switch flooding. Sometimes so severe that MULTICAST with IGMP support was invented, but it is (again) not an potion given here. By the way, in real server 2012 R2 console MULTICAST with IGMP is an option. Unicast mode does not cause any flooding, in that case not all switch ports receiving packets, only the ones who are promoted in switch ARP memory with Unicast MAC address.
      Concluding, right answers are: Affinity – SINGLE, Mode – Unicast.




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  2. kurt says:

    Snowden says:
    July 7, 2015 at 2:32 am
    Rick, you’re a bit confused it seems: Unicast *maximizes* port flooding! 🙂 The best way to deal with this is, like you say, by using IGMP Multicast. If the switches don’t support it, however, the next best approach is to use Multicast with *static* ARP entries.




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  3. kurt says:

    This should be Affinity=None and Mode=Multicast. As I understand it, in NLB the unicast mode spoofs the same MAC address across all the nodes in the cluster, so all traffic to the individual nodes has to be sent across every switch port because it doesn’t know which port to contact the individual node on. In Multicast however, the original MAC address is kept and the clusters shared MAC is assigned as an additional address on each node. This means internal traffic can still be sent to individual nodes, while cluster traffic is still sent to the shared MAC & reaches each node. This reduces the amount of port flooding, and can be further improved by IGMP multicast if the switches support it




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  4. Gilbert says:

    [b]Unicast[/b] – Each NLB cluster node replaces its real (hard coded) MAC address with a new one (generated by the NLB software) and each node in the NLB cluster uses the same (virtual) MAC. Because of this virtual MAC being used by multiple computers, a switch is not able to learn the port for the virtual NLB cluster MAC and is forced to send the packets destined for the NLB MAC to all ports of a switch to make sure packets get to the right destination

    [b]Multicast[/b] – NLB adds a layer 2 MAC address to the NIC of each node. Each NLB cluster node basically has two MAC addresses, its real one and its NLB generated address. With multicast, you can create static entries in the switch so that it sends the packets only to members of the NLB cluster. Mapping the address to the ports being used by the NLB cluster stops all ports from being flooded. Only the mapped ports will receive the packets for the NLB cluster instead of all ports in the switch. If you don’t create the static entries, it will cause switch flooding just like in unicast.




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