Increase the number of frames flooding in a VLAN.Īlso, because the dynamically learned MAC addresses need to stay current,Ĭatalyst switches have a mechanism to age out the MAC address table entriesĪfter a certain idle period. Nevertheless, there are configuration and spanning-tree events that might Unicast flooding is a normal and expected behavior of Ethernet LAN networks. This issue is known as unicast flooding.Ģ Switch Floods Traffic Sourced from PC-A to PC-D to All Interfaces If this flooding is happening for unicast frames, network performance Flooding to all ports in a VLAN always occurs for broadcastįrames.
MAC address hence, traffic from PC-A to PC-D is flooded to all interfaces in In Figure 2, the switch has not learned the PC-D The switch (that is, it is an unknown unicast), the switch floods the frame toĪll the interfaces in the VLAN. However, if the frame destination of the MAC address is not yet learned by Use the following command on Cisco IOS-based Catalyst switches to display theĭynamically learned MAC addresses for a specific VLAN: show mac-address-table dynamic vlan vlan-idįor CatOS-based Catalyst switches, use the following command to display theĭynamically learned MAC addresses for a specific VLAN: show cam dyanamic vlan-id Knows on which ports the PCs are located and, hence, is able to switch outįrames using the MAC address table without flooding the frame on all ports.ġ Switch Forwards Traffic Sourced from PC-A to PC-D Efficiently Maximum performance and efficiency is achieved if the switch already knows In addition, Catalyst switchesīuild MAC address tables used to forward frames at Layer 2 based on the unicast Troubleshoot these situations can significantly improve network performance.Ĭatalyst® Switches, at Layer 2, forward or switch frames based on theĭestination MAC addresses of the frames received.
Having the ability to identify and successfully
#Troubleshoot cisco mac address table how to
The followingĪrticle addresses how to detect and troubleshoot unicast flooding issues due to Unicast flooding occurs for many reasons in a switched network. Troubleshooting Unicast Flooding Due to Topology Changes
0 kommentar(er)
