#Cisco mac address table clearance mac#
The table shows that the switch adds the MAC address for PC-A to the MAC address table. In Figure 7-15, for example, PC-A is sending an Ethernet frame to PC-D. By default, most Ethernet switches keep an entry in the table for 5 minutes. If the source MAC address does exist, the switch updates the refresh timer for that entry. If the source MAC address does not exist, it is added to the table, along with the incoming port number.
It does this by examining the source MAC address of the frame and the port number where the frame entered the switch. Examine the Source MAC AddressĮvery frame that enters a switch is checked for new information to learn. The switch forwards frames by searching for a match between the destination MAC address in a frame and an entry in the MAC address table. Switch Learning and Forwarding (7.3.2)Ī switch dynamically builds its MAC address table by examining the source MAC addresses of the frames received on a port. While the term CAM table is fairly common, for the purposes of this course, we refer to it as a MAC address table. The MAC address table is sometimes referred to as a content-addressable memory (CAM) table. The table shows the MAC address table, which has not yet learned the MAC addresses for the four attached PCs. In Figure 7-14, the four-port switch was just powered on. In contrast, a legacy Ethernet hub repeats bits out all ports except the incoming port. The switch makes its forwarding decisions based solely on the Layer 2 Ethernet MAC addresses.Īn Ethernet switch examines its MAC address table to make a forwarding decision for each frame. It is completely unaware of the data (protocol) being carried in the data portion of the frame, such as an IPv4 packet, an ARP message, or an IPv6 ND packet. If a switch just forwarded every frame it received out all ports, your network would be so congested that it would probably come to a complete halt.Ī Layer 2 Ethernet switch uses Layer 2 MAC addresses to make forwarding decisions. Now that you know all about Ethernet MAC addresses, it is time to talk about how a switch uses these addresses to forward (or discard) frames to other devices on a network. Layer 3 switches are beyond the scope of this book.
This section focuses on Layer 2 switches. Although traditionally most LAN switches have operated at Layer 2 of the OSI model, an increasing number of Layer 3 switches are now being implemented. Do not use this command when the port is trunk or if you connect other switches on the specific port.Compared to legacy Ethernet hubs, Ethernet switches improve efficiency and overall network performance. Use it only if you connect a regular host (e.g Computer) on the port. “Portfast” bypasses the Spanning Tree states and brings the port up as quickly as possible. MySwitch(config)# copy running-config startup-config PortFast MySwitch(config-if)#switchport port-security violation shutdown MySwitch(config-if)#switchport port-security maximum 1 MySwitch(config-if)#switchport port-security mac-address sticky MySwitch(config-if)#switchport port-security Setting Web-based interface for configuration (GUI): MySwitch(config-if)#description TO SERVER Duplex and Speed Settings
MySwitch(config)#ip default-gateway 192.168.1.1 Setting IP Address (To allow remote access to the switch): MySwitch(config-line)#transport input telnet MySwitch(config-line)#transport input ssh MySwitch(config)#service password-encryption
#Cisco mac address table clearance password#
MySwitch(config)#username admin password csico1234 MySwitch(config)# Setting login credentials: The following commands will work on most Cisco switch models such as 4500, 3850, 3650, 2960, 3560 etc. NOTE: Other Cisco Command Cheat Sheet Posts:
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