If device A sends a data frame to the address 00000ABB28FC, the switch will fail to deliver this frame to the destination, as it has two recipients of this data frame.
WHAT IS CISCO MAC ADDRESS MAC
The NIC of devices B and C have the same MAC address. The MAC addresses of these devices are 11000ABB28FC, 00000ABB28FC, and 00000ABB28FC, respectively. Suppose three devices A, B, and C are connected to a network through a switch. If a LAN network has two or more devices with the same MAC address, that network will not work. Why should the MAC address be unique in the LAN network? We have the IP address to identify the device through different networks, we still need a MAC address to find the devices on the same network. On the other hand, the IP addresses are used on layer 3 and help identify the devices on different networks. The MAC address works on layer 2 and helps identify the devices within the same broadcast network (such as the router). When we request a page to load on the internet, the request is responded and sent to our IP address.īoth MAC and IP addresses are operated on different layers of the internet protocol suite. The answer to this question is that every mac address is assigned to the NIC of a hardware device that helps to identify a device over a network. Reason to have both IP and MAC addresses.Īs we already had the IP address to communicate a computer to the internet, why we need the MAC address.
It works on the data link layer of the OSI model.It is 12-digit, and 48 bits long, out of which the first 24 bits are used for OUI(Organization Unique Identifier), and 24 bits are for NIC/vendor-specific.It is represented in a hexadecimal format on each device, such as 00:0a:95:9d:67:16.
It is globally unique it means two devices cannot have the same MAC address.It stands for Media Access Control, and also known as Physical address, hardware address, or BIA (Burned In Address).It is assigned to the NIC (Network Interface card) of each device that can be connected to the internet. To make communication between two networked devices, we need two addresses: IP address and MAC address. MAC address is the physical address, which uniquely identifies each device on a given network.(ETA: What if you can't get to the Console port? How do you get the IP address of the switch in order to SSH or (if you must) Telnet in?)Ĭouldn't you just use CDP? #show cdp nei detail will show you the ip of the connected devices. The amazing thing to me is, this far into the 21st Century, this is still the only way I could find to get this information - i.e. Also, 'sh ip arp | i 0/24' will show just the MAC address(es) on that port.)
If you're all Cisco, 'show cdp neighbor' (or 'sh cdp nei') will get you to the next switch. (Small tip: When you see a large number of MAC addresses showing up on a single port, there's a switch on that port into which those MAC addresses are connected. It helps to Ping the subnet's broadcast address (e.g.
:^D After beating Google to death over it, hoping for some useful tool, I ended up using exactly the same process (plus the online MAC address lookup to ID the device manufacturer), so I can affirm this works perfectly, if you work it.Īs you can see, the 'sh arp' or 'sh ip arp' commands also give you the MAC addresses, so essentially the 'sh mac add' is only to get the port in which the device is connected. Thanks for posting this *after* I finished a "What's Connected Where" jihad on our network.
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