![]() ![]() Use the Telnet protocol to log into a Cisco Switch. Learning Objectives Upon completion of this lab, you will be able to: Lab 9.8.2: Cisco Switch MAC Table Examination Try Scribd FREE for 30 days to access over 125 million titles without ads or interruptions! Start Free Trial Cancel Anytime.ĬCNA Exploration Network Fundamentals: Ethernet This document document is Cisco Public Information. Some switches can also be configured for static MAC-port combinations, consult the manual.Lab 9.8.2: Cisco Switch MAC Table Examination Topology DiagramĪll contents are Copyright © 1992–2007 1992–2007 Cisco Systems, Inc. You should make sure that the node in question sends out a frame after link-up (or before it is eventually aged out), populating the switch's MAC address table (a link-down usually clears the addresses on that port). (The only thing an L2 switch potentially changes in a frame is the 802.1Q tag.) The point is that the "unknown" MAC continues to function normally, even if the whole network is polluted with frames addressed for that node. ![]() If the node in question has never send a frame, the bridge/switch cannot know its location and subsequently floods frames with that destination out of all its ports, mimicking a repeater hub.īut in no case does a switch alter an unknown destination address in a frame to the broadcast address. That is how a self-learning bridge works: it learns the location of nodes by the frames' source addresses and then forwards frames by the destination address based on the learned table. What behaviour are we seeing here? Isn't the switch meant to flood the packets with destination MAC, forcing the clients to read the packet contents to see if they are meant for them?Īlso, I would greatly appreciate any advice on what other checks I can perform. The switch is meant to save that MAC into its mac address table. This is an important point: the device with MAC continues to send frames with source MAC to the switch. Whilst this 'flooding' (is this actually flooding?) is happening, the device 192.168.0.20 continues to function well on the network! It is successfully transferring data. The mac address-table entries, however, are missing .Īfter restarting the device, the MAC address table entry gets re-created. In a Wireshark capture on host 192.168.0.10 with MAC I see packets with MAC destination and Destination IP 192.168.0.20ĪRP table on the switch contains a correct entry for 192.168.0.20, listing MAC of.It appears that a switch is sending the same traffic to all ports in a VLAN: ![]()
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