My Netwok Dictionary

A switch is a network device that acts as a Layer 2 concentration point for connecting workstations, servers, routers, hubs and other switches.

A hub is an older type of aggregation device that also has multiple ports. However, the hubs are lower than those switches as all devices connected to a hub share the bandwidth and have the same collision domain.

Another disadvantage is that only hubs operating in half-duplex mode. In half-duplex mode, the hubs can only send or receive data at some point but can not do both simultaneously. The switches can operate in full duplex mode, which means they can send and receive data simultaneously. Read the rest of this entry »

The isdn switch-type command can be executed in global configuration mode or interface configuration mode to specify the provider ISDN switch.

The configuration command of isdn switch-type in the global configuration mode defines the same type of ISDN switch for all ISDN interfaces. After running the global configuration command, each interface can be configured individually to reflect a different type of switch.

Once installed the ISDN service, the service provider will send information on the switch type and SPID. SPID are used to define the services available to each individual subscriber ISDN service. Depending on the switch, you may have to add these SPID to the configuration. The National ISDN-1 switches and DMS-100 ISDN configuration requires SPID, but not the AT & T 5ESS switch. You must specify the SPID when using Adtran ISDN simulator. Read the rest of this entry »

This article explains how the switches and bridges filter frames. In the terms switch and bridge are synonymous. Most bridges can filter frames based on any field Layer 2 frame. For example, a bridge can be programmed to reject, without sending, all frames that originate from a particular network. As the data link layer often includes reference to a higher layer protocol, bridges usually can filter based on this parameter.

In addition, filters can be useful for managing unnecessary broadcast packets and multicast. Once the bridge has created a local address table is ready to operate. When receives the frame, it examines the destination address. If the address of the story is local, the bridge passes by. If the frame is the address of another LAN segment, the bridge copies the frame to the second segment.

• Skipping a frame is called filtering.
• Copy the frame is called send.

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This article explains the default settings of a switch and how to verify it. At first light, a switch has default data in the active configuration file. The default hostname is Switch. Not set any password on the lines of console or virtual terminal (vty).

You may be granted to the switch IP address for management purposes. This is configured in the virtual interface, VLAN 1. By default, the switch has no IP address. The switch ports or interfaces are set to automatic mode and all switch ports are in VLAN 1. VLAN 1 is known as the management VLAN by default. Read the rest of this entry »

This article explains how the switches create and manage MAC address tables.
The switch examines the source address of frames that are received at the ports to learn the MAC address of workstations or PCs connected. These learned MAC addresses are recorded then a MAC address table. The frames that have a MAC address destination, which has been on the table, can be switched to the correct interface.

The command show mac-address-table can be entered in privileged EXEC mode to examine the addresses that a switch has learned. A switch dynamically learns and maintains thousands of MAC addresses. To preserve the memory and for optimal operation of the switch, the entries can be discarded learned the MAC address table. Read the rest of this entry »

It is possible that a switch is already preconfigured and only be made to passwords for user EXEC mode or privileged EXEC. You enter the configuration mode switch from the privileged EXEC mode.

In the CLI, the EXEC mode privileged default indicator is Switch #. In EXEC mode user indicator is Switch >.

The following steps will enable a completely new configuration overwrites the current configuration:

• To delete the current VLAN information, delete the file from the VLAN database, called vlan.dat flash directory.
• Erase the backup configuration file named startup-config.
• Reset the switch using the reload command.

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This article explains how bridges and switches learn addresses and send the frames. Bridges and switches need send only frames that travel from one LAN segment to another. To accomplish this task, these must learn which devices are connected to which segment of the LAN.

It is believed that a bridge is an intelligent device because it can make decisions based on MAC addresses. To do so, a bridge is consulting a table of addresses. When a bridge is turned on, messages are sent in broadcast stations asking all the local segment of the network to respond. As the answer stations broadcast the message, the bridge will create a table of local addresses. This process is called learning. Read the rest of this entry »

The routers must be configured to identify the type of switch which communicates. ISDN switch types available vary in part according to the country that uses the switch. As a result of the various implementations of Q.931, the signaling protocol used in the D channel ISDN switches varies between suppliers.

The services offered by ISDN providers vary considerably from one country to another and from one region to another. As modems, each type of switch operates slightly differently and has a specific set of requirements for the establishment of the call. Before you connect the router to the ISDN service must be configured for the type of switch. This information must be specified when configuring the router so that it can communicate with the switch, connect the call at the ISDN network and send data. Read the rest of this entry »

The construction of a LAN that meets the needs of medium and large organizations is much more likely to be successful if you use a hierarchical design model. This article discusses the three layers of hierarchical design model:

• The access layer provides workgroup users access the network.
• The layer of distribution offers policy-based connectivity.
• The core layer provides optimal transport between sites. The core layer is sometimes called a backbone.

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Functions of Layer 2 switches:

A switch is a device that connects LAN segments using a MAC address table to determine the segment to which a frame must be transmitted. Switches and bridges operate at Layer 2 of the OSI model.

Sometimes the switches are referred to as multi port bridges or switching hubs. The switches make decisions based on MAC addresses and therefore are Layer 2 devices. On the other hand, hubs regenerate the signal on Layer 1 and sent to all ports without making a decision. Read the rest of this entry »