Network load balancing and switching, arp, mac address, etc

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I am planning on setting up network load balancing for 2 web servers and I'm trying to understand how the cluster IP address works with the MAC addresses and ARP on a layer 2 managed switch. I've read a few Microsoft articles but it's still not very clear.

Let's say I ping the cluster IP address. The switch will look in its ARP table and see if there's a corresponding MAC address. once it figures out the mac address then it maps it to a port and I can look in the mac address table to figure out what port it's on.

How does the switch know what port to send the traffic to each time if the mac-address is bound to a specific port?

I have this problem too.
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satish_zanjurne Tue, 08/19/2008 - 21:51


If mac address is bound to one of the switch port, this entry will also be in mac-address-table of that switch as permanent/static entry.

So switch will do lookup and will find the corresponding port to send the traffic.

Rate it if your query is clear..

ohassairi Wed, 08/20/2008 - 00:31

the problem with microsoft network load balancing is that it uses multicast address. This can cause bad performance in switches (see:

Microsoft has given some solutions for this problem: see;en-us;193602

i think the best solution is to add static entries in mac address tables

I don't really use multicasting on my network. According to the MS article, you can use either Unicast or Multicast. Which one should I be using?

When creating the static mac-address-mappings for the ports the servers are connected to, how do I do that? (using port-security?)

One of the Microsoft Articles talks about doing an ARP static mapping. Is that the same thing as the mac-address-mapping for the ports?


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