Cisco Switch

What exactly is a Cisco switch, how does it function and what do switches do on an Ethernet network? These are questions a lot of people who want to understand computers and networks will want to know the answer too. If you have a Cisco switch, it will change Ethernet frames and work at Layer at Layer 2 of the OSI model, but not Layer 1 like a hub. It will only look at Ethernet MAC address information and will keep a table of these addresses that traverse the Cisco switch. The table is called the bridge forwarding table or CAM table. It will also keep a table of the addresses and what port they are on.

A Cisco switch will save bandwidth because it will only send traffic to the particular device that is the intended destination. Collisions are prevented because each device connected to the Cisco switch will get the full bandwidth of the switch port. This means that the bridge forwarding table is used by the switch to send intelligent traffic to the destination MAC address. However if the bridge forwarding table does not have the destination MAC address, the Cisco switch will flood the Ethernet frame ports on the switch to see what port responds to the flooded frame. Once the port is determined, that information will be added in the bridge forwarding table so that the destination MAC address will then be there the next time. If you want to take a look at the bridge forwarding table on a Cisco switch, type in “show mac-address-table and you will then be able to see it on your monitor screen.

There are various types of Cisco switches that include “dumb” switches and “managed” switches, chassis-based and layer 3 switches. Businesses usually prefer to use managed switches. This way they can get statistics on their switch traffic, trouble shoot connections, see the bridge forwarding table and hard-code port speeds and duplex.

Cisco is a trusted brand but there are many other brands available. They come in sizes that have just a few ports or all the way up to 96 ports or more. Some are very inexpensive and others can cost tens of thousands of dollars like the Cisco Catalyst 6500 series switch. Some switches are chassis-based and have blades called cards. These types of switches will also do intrusion detection, routing and other types of services. A Layer 3 switch can perform the function of a router but it does not have WAN ports. A business will usually use a Layer 3 switch when they want to use a VLAN to have logical networks that are segregated.

The port speed and duplex are important when it come to your Cisco switch. Some devices may have to go to your switch and hardcode the speed or duplex if the Auto negotiate can not find the best speed and duplex that is available to make the needed connection. A lot of administrators prefer to hard-code the port speed and duplex to prevent auto negotiation. This is because they want to have either a full duplex connection all the time or half duplex connections all the time so that devices can send and receive information at the same time without any trouble. If left alone to auto negotiate, there may be one device that is set at half duplex while the other one is set at full duplex connection. Duplex can be hard-coded and set at either half, full or auto-negotiate. When you have one device at half duplex and the other one at full duplex the connection may not work at all. This is why the network administrator will usually hard-code the duplex on the Cisco switch.

This Cisco Switch Review is Written/Updated on Jul 8th, 2010 and filed under Computer Hardware. Both comments and pings are currently closed.

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