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Cat6k switches and MS Network Load Balancing

We are about to get up MS Windows Network Load Balancing (WNLB) for a proxy array. The two array cluster members will be in different buildings connect to two different Cat6k switches, separated by a fibre link.

WNLB will be set up in "Multicast" mode, so a multicast MAC address exists to which clients address packets (all cluster members receive all packets, and WNLB decides which packets to discard, according to its load-balancing algorithm).

Therefore, any inbound packets will be flooded to all switch ports in the VLAN, and I cannot see a method of limiting this multicast traffic other than by placing these servers in a separate VLAN. Would it be possible to hard-wire static CAM entries into the switches to limit the multicast traffic (would static entries then be required on upstream switches)?

This may be less of an issue than I anticipate, as only inbound traffic will be flooded (reply traffic from the cluster members won't have multicast MAC addresses) and the cluster is for a proxy server array where less traffic is likely to be sent than received.

Incidentally, I see that Microsoft have improved WNLB in 2003 Server, and now IGMP can be used to limit the flooding of cluster-related multicast traffic on switch ports through IGMP snooping.


Re: Cat6k switches and MS Network Load Balancing

Why not create a /29 Subnet/VLAN (max 6 hosts) and just have the WNLB Servers & the Router (HSRP etc) that way you will limit the traffic as much as possible.


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