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New Member

Microsoft Windows Load Balancing (WLBS) on two Cat-6513

My network consist of Two backcone switches

Cat-6513 ( Sup2, SFM, and MSFC ), 40 Edge switches Cat-3550 ( inline power )

each edge switch connected to both backbone ( one

Gigabit up-link to each backbone )

I would like to install Two MS-Exchange Servers on this network ( connect One Server to each Backbone ) and use Microsoft Windows Load Balancing (WLBS) feature

Is this possible ? OR should I connect the servers to a hub

Can anyone help me in this issue ?

Thanks

Regards

Mohamed

7 REPLIES
Bronze

Re: Microsoft Windows Load Balancing (WLBS) on two Cat-6513

Mohamed,

Server issues aside :), this should work as long as your backbone switches are connected to each other and passing the VLAN the MS Exchange servers are on across that connection. Due to the behavior of the WLBS, I would recommend that you put the MS Exchange servers on their own (dedicated) VLAN. You can find more information here:

http://www.cisco.com/en/US/partner/tech/tk389/tk689/technologies_tech_note09186a008011b481.shtml

~Zach

New Member

Re: Microsoft Windows Load Balancing (WLBS) on two Cat-6513

Zach,

Thanks for your reply

Both servers will have the same MAC & IP addresses due to WLBS feature

I think this may casue a problem with the switches to see the same MAC addess on two ports on two different switches

How can I solve this issue ?

Regards

Mohamed

Bronze

Re: Microsoft Windows Load Balancing (WLBS) on two Cat-6513

Mohamed,

The WLBS will respond to ARP requests for the cluster IP address with the cluster MAC address. However, when an individual server sends traffic to the switch, it uses a substitue MAC address (not the cluster MAC address). This prevents the switch from ever associating the cluster MAC address with a particular switch port, which causes frames destined for the cluster MAC address to be flooded to every port in the VLAN.

~Zach

New Member

Re: Microsoft Windows Load Balancing (WLBS) on two Cat-6513

Zach,

Thanks for your help

Does this mean that this is no special configuration on the switches ? Just assign the ports ( connected to the two servers ) to the same VLAN ?

Is this is a configuration on the Servers ?

Regards

Mohamed

Bronze

Re: Microsoft Windows Load Balancing (WLBS) on two Cat-6513

Correct. The configuration is done on the servers. I believe the behavior I described is the default for WLBS, but you should verify.

~Zach

New Member

Re: Microsoft Windows Load Balancing (WLBS) on two Cat-6513

The way WLBS works is you have 2 servers and one nic a piece. WLBS creates a virutal mac and you assign a virtual IP. Our experience is that you get mutilple replies from the same IP. So, if you ping the IP you would see one SYN and multiple echo replies. The user still gets connected but it seems like a lot of traffic. Our own support calls into Microsoft tell us that this is how it works.

Now, if you want to administer the servers individually, you will have to add one more nic to each server with separate IP's or you will never be able to get into the server you want. This also creates replies when you ping the virtual IP. Sounds incorrect but again, this is coming from Tech Support from MS.

Because of this, I would recommend going with a hardware load balancer of some sort. These allow you to use a virtual IP on any port you want it to use and you can still access each server individually for administrative purposes.

WLBS does work and you can connect each nic (associated with the virtual address) to separate switches but we are weary of the multiple replies when the virtual address is accessed.

Hope this helps.

Mike Goodman

New Member

Re: Microsoft Windows Load Balancing (WLBS) on two Cat-6513

Thanks for your reply

How should I configure my Backbone Switches ?

each server will connect to one backbone switch

Regards

Mohamed Abdallah

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