Static ARP for Microsoft NLB Multicast on HPE Aruba ArubaOS-Switch

How to stop Microsoft NLB multicast traffic flooding on HPE Aruba ArubaOS-Switch using ip arp-mcast-replies and IGMP, with equivalent Cisco commands for reference.

1 min readUpdated KNET Ltd

Microsoft NLB in multicast mode causes switches to flood traffic to all ports because the multicast MAC address is never seen as a source — the switch cannot learn which port the cluster is on and treats it as an unknown destination.

HPE Aruba ArubaOS-Switch does not have a direct static MAC/ARP entry feature like Cisco, but ip arp-mcast-replies combined with IGMP resolves the flooding.

HPE Aruba solution #

cli
ip arp-mcast-replies

Enable IGMP on the NLB client VLAN, and ensure NLB is set to multicast cluster operation mode:

cli
vlan 10
  name "Client VLAN"
  ip igmp
exit
IGMP multicast mode in Microsoft NLB
IGMP multicast mode in Microsoft NLB

Apply on all switches in the campus, not just the directly connected switch.

Cisco equivalent (for reference) #

cli
arp x.x.x.x 0000.0000.0000 arpa
mac-address-table static 0000.0000.0000 vlan x interface Gix/x/x