testolz.blogg.se - How to show mac address table on cisco switch

Setting too long an aging time can cause the address table to be filled with unused addresses, which prevents new addresses from being learned. This unnecessary flooding can impact performance. Then, when the switch receives a packet for an unknown destination, it floods the packet to all ports in the same LAN (or VLAN) as the receiving port. Setting too short an aging time can cause addresses to be prematurely removed from the table. You can change the aging time setting for MAC addresses. Note: The MAC address table was previously referred to as content addressable memory (CAM) or as the CAM table.ĭynamic addresses are source MAC addresses that the switch learns and then ages when they are not in use. The figure shows a sample MAC address table from the output of the show mac-address-table command that includes static and dynamic MAC addresses. These MAC tables include dynamic and static addresses. Operation: Added Vlan: 28 MAC Addr: use MAC address tables to determine how to forward traffic between ports. History Index 0, Entry Timestamp 348747, Despatch Timestamp 348747 Maximum Number of entries configured in History Table : 1 Interval between Notification Traps : 1 secs MAC Notification Feature is Enabled on the switch Rack1SW2#show mac-address-table notification Rack1SW2#clear mac-address-table dynamic interface fa0/24 Verify SNMP MAC Address logging configuration: These traps are then forwarded to an NMS station located at 187.1.3.100 using the community string CISCOTRAP.

Then, these traps are selectively enabled on a per-interface basis by issuing the snmp trap mac-notifications interface level command. To enable SNMP trapping when a MAC address is added or removed from the CAM table, issue the global configuration commands mac-address-table notification and snmp-server enable traps MAC-Notification. Snmp-server host 187.1.3.100 CISCOTRAP MAC-Notification Snmp-server enable traps MAC-Notification

The network management server will be expecting community-string to be CISCOTRAP.

In order to help track down this device in the future configure SW2 to notify the network management station at 187.X.3.100 whenever a new MAC address is learned in VLAN 28.

After checking the MAC address tables of SW1 and SW2 you have determined that the notebook computer is not currently plugged into the network.

A recent security breach which involved the compromising of the company’s future business plans was tracked down to a notebook computer that was located in VLAN 28 with a MAC address of 0001.02ac.9ab2.Logging MAC addresses Augat 11:44 am | Posted in IOS services | 4 Comments