Microsoft NLB and Cisco 4507R

Unanswered Question
Mar 23rd, 2009
User Badges:

I was trying to follow this document for setting up my Cisco 4507R switch to support multicast mode for a Microsoft network load balancing.

But I am unable to assign the virtual NLB MAC address used by the cluster to multiple switch ports. I can however do it on a Cisco 2950. Is there anyway to make this work with the 4507R? Both of my servers are connected to it, and I would rather not have to stick another switch in the middle. I'm running the Supervisor Engine II-Plus.

My goal is to eliminate all of the flooding that the current unicast NLB mode is doing.


  • 1
  • 2
  • 3
  • 4
  • 5
Overall Rating: 0 (0 ratings)
tom_fox_ki4qqq Mon, 03/23/2009 - 15:51
User Badges:

Can you give us the commands you are having trouble with and the error that is occurring?

jplowick3 Tue, 03/24/2009 - 06:15
User Badges:

This is the command that I was trying to enter:

mac-address-table static vlan 1 interface g6/25 g6/33

On the 4507, it doesn't accept the second interface as an argument which I need.

tom_fox_ki4qqq Tue, 03/24/2009 - 06:56
User Badges:

If IOS detects a unicast MAC, it won't allow you to put in 2 interfaces on one line. I believe you can enter the same command twice, once for each NIC.

Is the MAC a multicast MAC address (i.e. begins with 01)?

jplowick3 Tue, 03/24/2009 - 07:13
User Badges:

Yes, it should have been a multicast MAC, although I don't recall what exactly it was. I used what the server had listed on the screen when we switched to multicast mode.

I just tried the command again on my switch but using a fake MAC starting with 01 and it accepted the command with multiple interfaces. Ugh.

Thanks for the pointer!

tom_fox_ki4qqq Tue, 03/24/2009 - 07:17
User Badges:

No problem. :) At least now you know the switch can do it.

If you can find a way to get MS to assign a true multicast MAC, that would be best.

Otherwise, I believe you can still do it by running the same command twice, once for each interface.

EDIT: Interestingly enough, I found this:

Note: Ensure that you use the multicast mode on the NLB cluster. Cisco recommends that you do not use multicast MAC addresses that begin with 01 because they are known to have a conflict with the IGMP setup.

from here:

So you may want to change your multicast MAC (if possible) to begin with 03.


This Discussion