Saturday, 10 November 2012

MAC Addresses

Media Access Control (MAC) is a hardware address that identifies every node in a network uniquely. The MAC address tables consist of the dynamic entries, which are derived when the switch examines the source of MAC addresses from the data frames, MAC address table include:

  • Dynamic Addresses: - Includes MAC addresses added to the MAC address table through normal switch processing. Depending on the port from where the data frame arrives, the MAC address is associated with the port. The entries in the table are cleared whenever the entire table is cleared.
  • Permanent MAC addresses: - Associates the MAC address with an incoming port similar to dynamic addresses. The Permanent entries never have a time out period.
  • Restricted-static entries: - Associates a MAC address with a particular part. Frames belonging to that MAC address must be entered through a particular set of incoming ports.

The 1900 series switches include the capacity to support 1024 MAC address. In addition, you must purchase the switches based on its capacity to support Layer 2 devices. You can configure static entries on a 1900 switch using the mac-address-table permanent command.

To populate the MAC address table on a 1900 switch:
  1. Open the switch CLI.
  2. Switch to the privilege mode.
  3. Switch to the configuration mode.
  4. Enter the following command, at the command prompt to configure static entries. Mac-address-table permanent 0444.4200.4200 e0/5.
  5. Enter the following command to exit the configuration mode. End
  6. Enter the following command to view the configuration of the MAC addresses.                                      Show mac-address-table.
Port Security

The Port Security feature of the MAC address table limits the number of MAC addresses associated with the port in the MAC address table. The function of this feature is to limit the number of sources that can forward frames into that particular switch port.

Configuration Files

The configuration can be stored in many locations. These locations can include the RAM, NVRAM, or a TFTP server. When a change in made to these switches, the changes occur in the RAM of those switch. These changes then can be saved into the NVRAM of those switches.

The commands that are used to manage configuration and system files are different on 1900 series switches than on the IOS based routers. The 1900 series switches have inherited many of IOS features, the difference being that it does not actually run on routers. The other difference in the 1900 series switches is that it automatically copies any changes made in the configuration into the NVRAM.