Configure and verify switch administration

Exam: Cisco 300-101 - CCNP Implementing Cisco IP Routing (ROUTE v2.0)

One important topic under the CCNP routing and switching exam is the layer 2 technologies. The topic how to configure and verify switch administration is an important part of this section. The exam is a closed book one and you are not allowed to refer any external materials must be kept in mind.

We will now discuss the topic in more details so that you can understand it better. As we all know that switch is a device that is used for making or breaking a connection in a network or an electric circuit. The term switch in this chapter will refer to a standalone switch and not to a switch stack. The switch stack is a set of up to 9 catalyst 3750 switches.

These are connected with the help of stackwise ports. One of the switches will control the operation of the whole stack and this is why it is called the stack master. This makes the other switches the stack members. The layer 2 and layer 3 protocols will present the whole switch stack as a one single entity for the whole network.

You must keep in mind that a switch cluster is very different from a switch stack. The switch cluster is a set of switches that are connected through their LAN ports. We will now move on to some topics that are associated with switch administration.

SDM templates

The SDM templates are used to configure system resources in the switch that will optimize the support for the specific features. This is done on the basis of how the switch is being used in the network.

One particular template can be used to ensure maximum system usage or you can use a default template for balancing the resources. The switch SDM template will prioritize the system resources that are used to optimize some features. The select SDM templates can be used to optimize the following features:

  1. Routing - The routing template will maximize the system resources for the IPv4 unicast routing. This is typically required for a router that is in the centre of the network.
  2. Default - The default template gives a balance to all the functions.
  3. Access - The access template will maximise the system resources for the ACL (access control list) this will accommodate a large number of ACLs.
  4. VLAN -The VLAN template is one that will disable the routing and support the maximum number of MAC addresses. This will be typically selected for a layer 2 Switch.

There is also a dual IPv4 and IPv6 templates will enable dual stack environment. Each template will generally have two versions. One is the desktop template and the other is aggregator template. The catalyst 3750-12s switch is capable of using the larger TCAM size that is available in the aggregator template. The other catalyst 3750 switch will support the desktop templates. If the desktop keyword is not used the aggregator template will be selected automatically.

All the stack members will generally use the same SDM template which is stored in the stack master. You must know that when a switch is added to the stack with the VLAN database file and switch configuration then the SDM configuration that is stored on the stack master will automatically override the templates that are configured on the individual switch.

As a network administrator you must remember that if change the template from a desktop template to a aggregator template and reload the switch then the whole desktop switch that was a part of the stack will go into a SDM mismatch mode.

If this happens a syslog message will be sent to the stack master that will indicate that a stack member has gone into a SDM mismatch mode. This will also suggest the steps that must be followed to bring the switch out of the mismatch mode.

The command that you can use to see if the stack members are in a SDM mismatch mode is "show switch privileged EXEC" command. To configure the

Managing MAC address table

The MAC address table contains the address information which the switch uses to forward the traffic between the ports. All the MAC addresses in an address table will be generally associated with one or multiple ports. The address table will basically contain the following types of addresses and these are:

  1. Static address that is a manually entered address that will not age nor get lost when the switch is reset.
  2. Dynamic address is a source MAC address that the switch will learn and will age when it is actually not in use.

The address table will list the destination MAC address, the port number and the associated VLAN ID along with the address type and address. With the help of multiple MAC addresses that support all ports you can connect any port on the switch to the individual switches, routers, workstations and even other network devices.

The switch allows dynamic addressing by understanding the source address of the packets received and adding these to the associated port numbers in the address table. As the stations are added and removed from the network, the switch will update the address table automatically.

Using the MAC address table the switch will forward the packet only to the port that is associated with the destination address. If the destination address is on the port that sent the packet then the packet will be filtered but will not be forwarded.

The MAC address tables on all the stack members are synchronised. This is why at any time each stack member will have the same copy of the address tables for each VLAN. If the address ages out the address is removed from the address table that is there on all the stack members. You can change the aging time for all the VLANs or for a particular VLAN.

The MAC addresses change notification and track the users on a network. They do so by storing the MAC address change activity. The MAC address change notifications are generated for the secure and dynamic MAC addresses only.

We hope that this chapter on how to configure and verify switch administration will help you to prepare better for the CCNP exam and also get a better score.

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