- Switch mac address learning spanning tree how to#
- Switch mac address learning spanning tree update#
- Switch mac address learning spanning tree Pc#
Switch mac address learning spanning tree update#
(A is on link X.)Ī split-second later, switch 2 receives the exact same frame on link Y this time, it causes a new update to the forwarding table.
Switch mac address learning spanning tree Pc#
The following sequence of events occurs when an application on the top PC (MAC address A) communicates with the bottom PC (MAC address B):ġ The top PC sends a frame to the bottom PC (destination MAC address B).Ģ Switch 1 learns that MAC address A is off port 0/1.ģ Switch 1 looks up MAC address B no match is found.Ĥ Switch 1 sends out the frame on link X and Y (a process known as flooding).ĥ Switch 2 receives the frame from A to B on link X and updates its forwarding table. A legitimate Ethernet MAC address is actually made up of 6 bytes. In the next steps, MAC addresses are conveniently shortened to a single-letter format for clarity. The figure represents a simple network composed of two LAN switches interconnected by two Ethernet links. Although this is perfectly fine in a single-switch environment, interesting side effects are observed in multiswitch topologies, as Figure 3-1 shows. That is, it sends a copy of the frame to every single port in VLAN X (except the port that originally received the frame). When an Ethernet frame arrives on a switch port in VLAN X with a destination MAC address for which there is no entry in the forwarding table, the switch floods the frame. Ĭonfig Times :Hello 2s MaxAge 20s FwDly 15s MaxHop 20Īctive Times :Hello 2s MaxAge 20s FwDly 15s MaxHop 20ĬIST Root/ERPC :32768.4c1f-cc7e-7e4d / 20000ĬIST RegRoot/IRPC : 32768.Chapter 2, "Defeating a Learning Bridge's Forwarding Process," explained how Ethernet switches build their forwarding tables by learning source MAC addresses from data traffic. The mac address under the Bridge ID is the one used for spanning tree calculation.īridge ID Priority 32769 (priority 32768 sys-id-ext 1)
Hello Time 2 sec Max Age 20 sec Forward Delay 15 sec Hardware is EtherSVI, address is 000.0001.0800 (bia 000.0001.0800)Ģ: You could also just check spanning tree for the calculation directly: Show span vlan 1 | b Bridge ID You will notice all of the SVIs have the same mac address. This will give you your "base" mac address. You could do this on a Cisco switch as follows: You can determine the base mac address and then calculate what the bridgeID will be for a particular VLAN based on the concept that the bridge ID for a particular VLAN will be the base Bridge ID + the vlan number. It is also good to remember that newer switches can use an extended system ID which is more than just the mac-address (as the other poster noted). You can figure out what the bridge ID will be for a VLAN once you have determined what the assigned mac-address is. You should first know that most Cisco switches will assign a unique bridge ID per VLAN based on a mac-address assigned to the switch. If you haven't already you might want to check out:īy Priscilla Oppenheimer, Joseph Bardwell STP generally is implemented using BPDU or bridge protocol data unit.
Switch mac address learning spanning tree how to#
The answer above is more of a how to translate an ip address to a MAC address, as that sounds like the gist of your question. You will receive a packet back mapping the ip address requested to the MAC address which owns that ip address. Find the ip address of the switch you want, then send an ARP request to that ipaddress.