Microsoft NLB
There are 3 modes to Microsoft Network Load Balancing (NLB)
1.Unicast
2.Multicast
3.IGMP multicast (check the IGMP checkbox in the GUI while in multicast mode)
In general,every mode uses a different sending and receiving mac address while keeping the unicast virtual IP address (VIP) constant across all 3 modes. This concept makes switches flood traffic at layer 2 since the switch either never sees the destination mac address come in on any of its ports(and hence can’t learn it) or the multicast mac address floods. Either multicast mode, IGMP or normal multicast, also requires static ARP entries on the gateway router since Cisco routers will not learn an ARP reply with a multicast mac address tied to a unicast ip address.
Mac addresses in the 3 modes breakdown into the following components:
The first number in the mac address is the type of NLB configuration: 01=IGMP, 02=Unicast, 03=Multicast (Note: bit 2 is the administered locally multicast space)
The second number, (bf) is the same for unicast and multicast mode (not IGMP multicast mode which uses the standard 01-00-5e mac address)
The last two (IGMP multicast mode) or four (unicast or multicast mode) numbers are the virtual IP address, i.e. c0=192, a8=168, 04=4, 0a=10 and thus the IP of 192.168.4.10 has a multicast mac address 03-BF-C0-a8-04-0a while an IGMP multicast mac address would be 01-00-5e-7f-04-0a
http://communities.cisco.com/message/76797
...
Mcast try to avoid unicast MAC oddities using a "proper" L2 mcast address but..yes but..there are problems dealing with switches since most L3 switches does not like multicast MAC with unicast IP and you have to create statics arp for NLB vip
Multicast/IGMP try to fix the flood of mcasts traffic only on ports that are members of a IGMP registered group..you should have IGMP support on L3 switches
We work mostrly with VMWare setups and mcast is the only reliable solution
For Cisco catalyst:
mac address-table static 03bf.0a9c.0284 vlan 10 interface Po2.
Nexus 7000
mac address-table multicast 03bf.xxxx.xxxx vlan interface
1.Unicast
2.Multicast
3.IGMP multicast (check the IGMP checkbox in the GUI while in multicast mode)
In general,every mode uses a different sending and receiving mac address while keeping the unicast virtual IP address (VIP) constant across all 3 modes. This concept makes switches flood traffic at layer 2 since the switch either never sees the destination mac address come in on any of its ports(and hence can’t learn it) or the multicast mac address floods. Either multicast mode, IGMP or normal multicast, also requires static ARP entries on the gateway router since Cisco routers will not learn an ARP reply with a multicast mac address tied to a unicast ip address.
Mac addresses in the 3 modes breakdown into the following components:
The first number in the mac address is the type of NLB configuration: 01=IGMP, 02=Unicast, 03=Multicast (Note: bit 2 is the administered locally multicast space)
The second number, (bf) is the same for unicast and multicast mode (not IGMP multicast mode which uses the standard 01-00-5e mac address)
The last two (IGMP multicast mode) or four (unicast or multicast mode) numbers are the virtual IP address, i.e. c0=192, a8=168, 04=4, 0a=10 and thus the IP of 192.168.4.10 has a multicast mac address 03-BF-C0-a8-04-0a while an IGMP multicast mac address would be 01-00-5e-7f-04-0a
http://communities.cisco.com/message/76797
...
Mcast try to avoid unicast MAC oddities using a "proper" L2 mcast address but..yes but..there are problems dealing with switches since most L3 switches does not like multicast MAC with unicast IP and you have to create statics arp for NLB vip
Multicast/IGMP try to fix the flood of mcasts traffic only on ports that are members of a IGMP registered group..you should have IGMP support on L3 switches
We work mostrly with VMWare setups and mcast is the only reliable solution
For Cisco catalyst:
mac address-table static 03bf.0a9c.0284 vlan 10 interface Po2.
Nexus 7000
mac address-table multicast 03bf.xxxx.xxxx vlan interface