ccna 200-301 network simulator toolstation

ccna 200-301 network simulator toolstation.(2) Bridge (Bridge)Bridges work at the data link layer and are used to connect two LANs together and forward frames by MAC address. The physical layer hubs can scale the network, but all hosts connected through the hubs belong to the same conflict domain, only one host can send data at any time, if there are two hosts sending data at the same time there will be a conflict, resulting in data sending failure. When the amount of data from the hosts in the same conflict domain is very large, the possibility of data conflict increases greatly, and a bridge can be used to separate the conflict domains at this time. A bridge can be used to separate conflict domains by separating a conflict domain into two conflict domains, reducing the likelihood of conflict by increasing the number of conflict domains and reducing the size of each conflict domain. A bridge connecting two network segments can transmit complete and correct frames from one segment to the other without transmitting interfering or faulty frames.Bridges are primarily used to interconnect Ethernet segments, transmitting information that needs to be transmitted between two different segments, but blocking information within a local segment, so the bridge reduces the total amount of traffic on the network.Figure 2-3-4 includes two hubs, four computers, and one bridge. Each bridge maintains a dynamic MAC address table, often called CAM (Content Addressable Memory), consisting of the MAC address of the site and the bridge's port number. Initially, this MAC address table is empty, and MAC address information is acquired later through learning methods. When a data frame arrives at the bridge, the bridge adds or refreshes a * record to the MAC address table based on its source MAC address and the port number of the arrival.AAAAAAAAAAAA money collector A BBBBBBBBBBBBBBCCCCCCCCCCCCC set na B DDDDDDDDDDDDDDFigure 2.3-4 Diagram of how the bridge worksThe bridge works as follows.1 When it is first powered up, the bridge's MAC address table is empty, suppose computer A (192.168.1.1) wants to send data to computer B (192.168.1.2),computer A encapsulates the packet (assuming computer A already knows computer B's MAC address, which will be described in section 242 on how computer A gets computer B's MAC address), sends the packet Computer A sends the packet to hub A, which sends the packet to all ports except the receiving port (Computer B and the bridge).2 After the bridge receives this packet, it first adds the source MAC address of this frame in the MAC address table, that is, the MAC address of computer A "AAAAAAAAAAAAA" and the corresponding port 1, then the bridge looks up the destination MAC address in this frame in its own MAC address table, that is " BBBBBBBBBBBBBB", but it does not find it, and the bridge forwards this packet out of port 2. The packet from the bridge port reaches hub B, which forwards the packet out from a port other than the incoming port. Computer C and Computer D receive the packet and check it, but find that the destination MAC address in the frame is different from the MAC address of their own NICs.