Application Example; Configuring The Mac Learning Limit On Ports - H3C S3600V2 SERIES Layer 2-Lan Switching Configuration Manual

Step
1. Enter system view.
2. Disable MAC entry aging
timer refresh based on
destination MAC address.

Application example

Microsoft Network Load Balancing (NLB) is a load balancing technology for server clustering developed
on Windows Server.
Figure 5 NLB cluster
NLB supports load sharing and redundancy among servers within a cluster. To implement fast failover,
NLB requires that the switch forwards network traffic to all servers or specified servers in the cluster, and
each server filters out unexpected traffic.
In NLB unicast mode, when a server joins the cluster or a failover occurs, a packet with a virtual source
MAC address is sent within the cluster. The switch then adds the virtual MAC address to its MAC address
table, and packets destined for the server use the virtual MAC address (although not used by the server)
as their destination address. If the virtual MAC address never ages out, the switch forwards packets only
through the port associated with the virtual MAC address rather than all ports connected to the servers
within the cluster.
To address this issue, disable MAC entry aging timer refresh based on destination MAC address to age
out the virtual MAC address, so that the switch can forward packets to all servers within the cluster.

Configuring the MAC learning limit on ports

To prevent the MAC address table from getting too large, you can limit the number of MAC addresses
that a port can learn.
To configure the MAC learning limit on a Layer 2 Ethernet interface or all ports in a port group:
Step
1. Enter system view.
Command
system-view
mac-address destination-hit
disable
Device
cluster
NLB
Command
system-view
Remarks
N/A
By default, MAC entry aging timer
refresh based on destination MAC
address is enabled.
Remarks
N/A
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