630 | Layer 2w w w . d e l l . c o m | s u p p o r t . d e l l . c o m Default BehaviorWhen an ARP request is sent to a server cluster, either the active server or all of the servers send a reply,depending on the cluster configuration. If the active server sends a reply, the Dell Force10 switch learns theactive server’s MAC address. If all servers reply, the switch registers only the last received ARP reply, andthe switch learns one server’s actual MAC address (Figure 29-3); the virtual MAC address is neverlearned.Since the virtual MAC address is never learned, traffic is forwarded to only one server rather than theentire cluster, and failover and balancing are not preserved (Figure 29-4).Figure 29-3. Server Clustering: Multiple ARP RepliesFigure 29-4. Server Clustering: Failover and Balancing Not PreservedConfiguring the Switch for Microsoft Server ClusteringTo preserve failover and balancing, the Dell Force10 switch must learn the cluster’s virtual MAC address,and it must forward traffic destined for the server cluster out all member ports in the VLAN connected tothe cluster. To ensure that this happens, you must configure the command vlan-flooding on the DellForce10 switch at the time that the Microsoft cluster is configured (Figure 29-5).VLAN 1 ClientLast ARP ReplyMACS1Server1: IPS1MACS2IPS2Server2:Source MAC: MACClusterDestination MAC: MACClientSource IP: IPS1Source MAC: MACS1Type: 0x0806Pad CRCEthernet Frame Header ARP ReplyfnC0027mpMicrosoft Server Cluster: IPClusterMACClusterMACS3IPS3Server3:MACS4IPS4Server4:VLAN 1 ClientDatafnC0028mpMACS1Server1: IPS1MACS2IPS2Server2:Microsoft Server Cluster: IPClusterMACClusterMACS3IPS3Server3:MACS4IPS4Server4:
