請登入Cisco Error Message Decoder網站
http://www.cisco.com/cgi-bin/Support/Errordecoder/index.cgi

將錯誤代碼%SYS-4-P2_WARN 輸入
http://www.cisco.com/cgi-bin/Support/Errordecoder/index.cgi?action=search&index=all&locale=en&query=%25SYS-4-P2_WARN&counter=0&paging=5&links=reference&sa=Submit

查到的訊息如下

2. %SYS-4-P2_WARN: 1/Filtering Ethernet MAC address of value zero Problem
   The switch is generating Filtering Ethernet MAC address of value zero messages. This is an example of the syslog output that you see when this error occurs: %SYS-4-P2_WARN: 1/Filtering Ethernet MAC address of value zero from agent host table interface %SYS-4-P2_WARN: 1/Filtering Ethernet MAC address of value zero from agent host table interface The Filtering Ethernet MAC address of value zero syslog message is generated when the switch receives packets with a source MAC address of 00-00-00-00-00-00, which is an invalid source MAC. The syslog message indicates that the switch refuses to learn the invalid address. However, the switch forwards traffic sourced from an all-zeros MAC address.

Recommended Action: The workaround is to try to identify the end station that is generating frames with an all-zeros source MAC address. Typically, such frames are transmitted from a traffic generator (for example, Spirent SmartBits), certain types of servers (such as load-balancing IBM WebSphere servers), a misconfigured router or end station (for example, a device transmitting all-zeros broadcasts), or a faulty NIC.

Related documents-

Understanding and Troubleshooting HSRP Problems in Catalyst Switch Networks

Common CatOS Error Messages on Catalyst 4500/4000 Series Switches

Understanding and Troubleshooting Astro/Lemans/NiceR Timeouts on Catalyst 4000/4500 Series Switches

Common CatOS Error Messages on Catalyst 6500/6000 Series Switches

看 Recommended Action 建議採取的行動 這部份就好，大意是需要找到MAC全部為0的這一個設備(可能是load-balancing IBM WebSphere servers，或是設定錯誤的Router)把他排除掉就可以解決。