A cisco switch is a layer 2 device that forwards traffic between ports based on the destination mac address of the frames. A cisco switch can perform two types of actions, filtering and throttling.
Filtering is the process of blocking traffic from passing through a port on the switch. This can be done based on various criteria, such as the source or destination mac address, the type of frame, or the VLAN the frame is a member of.
Throttling is the process of slowing down the rate at which traffic is forwarded through a port on the switch. This can be done for various reasons, such as to prevent congestion, or to give priority to certain types of traffic.
How does a cisco switch forward traffic?
A cisco switch is a device that allows for the forwarding of traffic on a cisco network. The switch looks at the destination address of each packet and then compares it to a table of known addresses. If the switch knows the address, it will forward the packet to the next hop. Otherwise, the switch will flood the packet out all ports except the port on which it was received.
How does a cisco switch learn about MAC addresses?
Whenever a frame is received on a port, the source MAC address of that frame is learned and associated with the ingress port. If the MAC address is already learned on a different ingress port, then the device will update its forward information to point to the correct egress port for that MAC address. The device canaging feature causes the device to periodically remove stale MAC address and port information from the device's forwarding database.
How does a cisco switch handle broadcasts?
A cisco switch handle broadcasts by comparison. The switch looks at the Layer 2 header of each frame that arrives on a port and compares the destination address with the addresses in its MAC address table. If the switch finds a match, it sends the frame out of the port associated with that address. If the switch doesn't find a match, it sends the frame out of all the ports except the one on which the frame arrived.
This process is known as broadcast forwarding and is the most efficient way to handle broadcasts. Broadcast forwarding reduces the number of broadcasts that are forwarded and thus reduces the amount of traffic on the network.
How does a cisco switch handle collisions?
A cisco switch handles collisions by discarding the damaged frames and continuing to listen for valid frames. It then retransmits the valid frames it receives.
Frequently Asked Questions
How do switches forward data between ports?
In store-and-forward switching, the switch receives the entire frame, computes the CRC, and stores the frame for processing by the forwarding engine. The forwarding engine then forwards the frame based on the destination MAC address in the header.
How does a frame forwarding switch work?
A switch forwards a frame according to the destination address, as determined by the CRC.
Is port forwarding with a Cisco router a good option?
Yes, if you need a low-cost option or want to remote-access your network from a different location. However, be aware that port forwarding with a Cisco router isn’t the most secure option – it’s better to use a dedicated security server.
What is the difference between Layer 3 forwarding and switch forwarding?
L3 forwarding involves a router or layer3 device that processes packet forwarding decisions. In contrast, switch forwarding is the process of switching packets between different interfaces on a switch.
How does a switch decide which port to use to forward frames?
The switch uses the destination MAC address in a frame to determine which port to send the frame onto. MAC Bridges A MAC bridge forwards frames based on the source IP address of the frame. This means that each device on the network forwards frames only based on its own network addresses, not by using the MAC addresses of other devices. The advantage of this approach is that it prevents bridging loops—if one device sends a frame to another device and that second device is also addressing another device, routers at both devices will drop the packet because they’re expecting a different type of packet (a broadcast or multicast frame, for example). However, MAC bridges are less efficient than switch forwarding because they don’t take into account how many pieces of data are in a frame. Figure 11-1 illustrates this concept. Figure 11-1: How MAC bridges work In Figure 11-1, Device A is sending information to Device B. In order
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