Ben Ari's UAG and IAG Blog

Plenty of useful and fun info on UAG, Microsoft's remote access and reverse-proxy product.

NLB modes supported by UAG

NLB modes supported by UAG

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A question that often comes up is which modes of NLB does UAG support. Initially, before UAG SP1 came out, support was limited to Unicast, even though the UAG User Interface allowed the user to select all 3 modes (Unicast, Multicast and or IGMP Multicast). To add to the confusion, there were some blog posts and other documents that contradicted each other.

To make this clear, we have edited the public documentation on this topic to say “From Forefront UAG SP1, Forefront UAG DirectAccess supports NLB in Unicast, Multicast, and IGMP Multicast modes.” To be clear, this means that for non DirectAccess (meaning Application Publishing scenarios), only Unicast is supported. In other words, if you are creating trunks on your UAG server, you can assign regular IPs, or VIPs configured with Unicast, but *not* VIPs configured with Multicast or IGMP Multicast. If you are configuring DirectAccess, you can assign any IP or VIP to the DA configuration, no matter which type of casting they use. If the UAG server has both Application publishing and DirectAccess, the same rule applies – Unicast only to the trunk or trunks, anything to the DA configuration.

If you run into any other source of information that contradicts the above, please notify me, so I can have it corrected.

  • small typo, NLA instead of NLB ^^

    Thanks for the info.

  • In this documentation, both three modes are offered for NLB: I think we already implemented NLB in Multicast Mode for trunks with no further problem, could that be? (obvously with the adequated router configuration).

  • Hi Ben,

    Can you provide the rationale behind supporting all modes for DA, but only unicast for publishing?



  • Hi Ben,

    Will the behaviour of supporting only unicast mode for publishing change in UAG sp3?


  • In response to Ashish's question: No, this is not going to change in UAG SP3.

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