Lenovo Flex System Fabric CN4093, Application Manual

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© Copyright Lenovo 2017 Chapter 20: Static Multicast ARP
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Chapter 20. Static Multicast ARP
The Microsoft Windows operating system includes the Network Load Balancing
(NLB) technology that helps to balance incoming IP traffic among multi ‐ node
clusters. In multicast mode, NLB uses a shared multicast MAC address with a
unicast IP address. Since the address resolution protocol (ARP) can map an IP
address to only one MAC address, port, and VLAN, the packet reaches only one of
the servers (the one attached to the port on which the ARP was learnt).
To avoid the ARP resolution, you must create a static ARP entry with multicast
MAC address. You must also specify the list of ports through which the multicast
packet must be sent out from the gateway or Layer 2/Layer 3 node.
With these configurations, a packet with a unicast IPv4 destination address and
multicast MAC address can be sent out as per the multicast MAC address
configuration. NLB maps the unicast IP address and multicast MAC address as
follows:
Cluster multicast MAC address: 03 ‐ BF ‐ W ‐ X ‐ Y ‐ Z; where W.X.Y.Z is the cluster
unicast IP address.
You must configure the static multicast ARP entry only at the Layer 2/Layer 3 or
Router node, and not at the Layer 2 ‐ only node.
Enterprise NOS supports a maximum of 20 static multicast ARP entries.
Note:
If you use the ACL profile or IPMC ‐ OPT profile, an ACL entry is consumed
for each Static Multicast ARP entry that you configure. Hence, you can configure a
maximum of 640 ACL and multicast MAC entries together.The ACL entries have a
higher priority. In the default profile, the number of static multicast ARP entries
that you configure does not affect the total number of ACL entries.