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WLAN Microsoft NLB Conundrum

Good afternoon All

Situation:
I have 2 subnets x.x.32.x and x.x.35.x with a wlan in between, on the 35.x end I have a Dell 6224 and on the 32.x end I have a HP 3400cl.  I have a web host on the 35.x and a 2 x wcf apps server on the 32.x with MS load balancing - the web host needs to connect to the 32.x wcf servers.  Both ends are VMs on VMware hosts.

Problem:
The web host can connect to the wcf if it used the NIC IP but is unable to connect to the NLB IP.  

On the Dell switch I can add static ARP entries but on the HP switch I only have the option of Proxy-ARP (unless someone knows different).
I cam across an option of adding a second NIC to the pair of WCF servers and altering the vSwitch but that will only work if I keep both servers on a single host, which sort of negates the reason for having them on separate hosts.

Could anyone give me a suggestion on how to achieve this connection without compromising my network or breaking anything else.?

Many thanks
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Eric
Asked:
Eric
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1 Solution
 
asavenerCommented:
What's the network topology at the 32.x site?  It's the layer 3 device that I'm concerned about.
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EricIT Systems and Asset ManagerAuthor Commented:
Hi Asavener

The layer 3 device we use for routing is the HP3400cl - it routes the traffic through the Huawei to the 35.x site.

Thanks
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asavenerCommented:
So that's the device that won't let you add a static ARP entry for the NLB address?
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asavenerCommented:
OK, according to the documentation for that model switch, it should support static ARP entries, but they only get added to the ARP table when the interface comes up:


ftp://ftp.hp.com/pub/networking/software/6400-5300-4200-3400-AdvTrafficMgmt-Oct2006-59906051-Chap11.pdf

A static entry enters the ARP cache from the static ARP table (which is a separate table) when the interface for the entry comes up
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EricIT Systems and Asset ManagerAuthor Commented:
Hi Asavener

There is no way to add static entries, and the dynamic entry only seems to pick up the host IP and mac not the load balancing IP and mac - in IPConfig it shows the nic as having 2 IP addresses not a real card and a NLB virtual card.  The wcf apps servers are virtual machines so they are not connected directly to the HP3400.
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asavenerCommented:
I suggest you contact the vendor, because the documentation indicates that static ARP entries are possible.

This is a "normal error" for layer three devices.  Cisco has an article on why their devices reject dynamic ARP replies from NLB clusters.  (Basically, it's a mis-match between multicast MAC address in the ARP reply and the unicast IP address of the NLB cluster address.)

Unless you're able to add a static ARP entry on your router/layer3 switch, only local hosts will be able to communicate with the NLB cluster.



Here's a good article describing the problem:  http://kb.vmware.com/selfservice/microsites/search.do?language=en_US&cmd=displayKC&externalId=1006525
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EricIT Systems and Asset ManagerAuthor Commented:
Many thanks for you help with this asavener, the links you supplied were very useful.
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