Spanning-Tree Protocol is a link management protocol that provides path redundancy while 
preventing undesirable loops in the network. For an Ethernet network to function properly， only one active path can exist between two stations. Multiple active paths between stations cause loops in the network. If a loop exists in the network topology， the potential exists for duplication of messages. When loops occur， some switches see stations appear on both sides of the switch. This condition confuses the forwarding algorithm and allows duplicate frames to be forwarded. To provide path redundancy， Spanning-Tree Protocol defines a tree that spans all switches in an extended network. Spanning-Tree Protocol forces certain redundant data paths
into a standby （blocked） state. If one network segment in the Spanning-Tree Protocol becomes unreachable， or if Spanning-Tree Protocol costs change， the spanning-tree algorithm reconfigures the spanning-tree topology and reestablishes the link by activating the standby path. Spanning-Tree Protocol operation is transparent to end stations， which are unaware whether they are connected to a single LAN segment or a switched LAN of multiple segments.There is a lab about STP in Cisco CCNP 642-812 / 642- 892 exam.

Requirements: 
You will configure FastEthernet ports 0/12 through 0/24 for users who belong to VLAN 20. Also, all VLAN and VTP configurations are to be completed in global configuration mode as VLAN database mode is being deprecated by Cisco. You are required to accomplish the following tasks: 
1. Ensure the switch does not participate in VTP but forwards VTP advertisements received on trunk ports. 
2. Ensure all non-trunking interfaces (Fa0/1 to Fa0/24) transition immediately to the forwarding state of Spanning-Tree. 
3. Ensure all FastEthernet interfaces are in a permanent non-trunking mode. 
4. Place FastEthernet interfaces 0/12 through 0/24 in VLAN 20

Acme is a small shipping company that has an existing enterprise network comprised of 2 
switches；DSW1 and ASW2. The topology diagram indicates their layer 2 mapping. VLAN 40 is a new VLAN that will be used to provide the shipping personnel access to the server. For security reasons， it is necessary to restrict access to VLAN 20 in the following manner： 
- Users connecting to ASW1’s port must be authenticate before they are given access to the network. -Authentication is to be done via a Radius server：
- Radius server host： 172.120.39.46
-Radius key： rad123 
- Authentication should be implemented as close to the host device possible. 
- Devices on VLAN 20 are restricted to in the address range of 172.120.40.0/24. 
- Packets from devices in the address range of 172.120.40.0/24 should be passed on VLAN 20. 
- Packets from devices in any other address range should be dropped on VLAN 20. 
- Filtering should be implemented as close to the server farm as possible. 
The Radius server and application servers will be installed at a future date. You have been tasked with implementing the above access control as a pre-condition to installing the servers. You must use the available IOS switch features.
 

topology exhibit： 
 

 
You work as a network engineer at . is a large international company with offices on all continents. You work at the Chicago Office. Your boss at ，Miss ，has asked you to install a Catalyst 3500 to provide for another 24 users. Your instructions are as follows： 
* install it in an IDF 
* extremely import to have the proper configuration of the Catalyst before it is placed into the product information 
* it should not participate in VTP 
* it should forward VTP advertisements that are received on trunk ports 
* all nontrunking interfaces， Fa0/1 to Fa0/24） should immediately to the forwarding state of the Spanning tree. 
* configure all Fast Ethernet ports （the user ports） such as they are nontrunking. 
* the fastEthernet interfaces 0/12 through 0/24 should be placed in VLAN 20

Network topology exhibit： 
 

You work as a network administrator at . You study the network topology exhibit carefully. is a small 
company that has an existing enterprise network consisting of two switches named 1 and 2. The network topology schemata indicates their layer 2 mapping. VLAN 40 is a new VLAN that will be used to provide the shipping personnel access to the server. For security reasons， it is necessary to restrict access to VLAN 20 in the following manner： 
Users connecting to 1’s port must be authenticate before they are given access to the network. Authentication is to be done via a Radius server： 
Radius server host： 172.120.39.46 
Radius key： key 
Authentication should be implemented as close to the host device possible. 
Devices on VLAN 20 are restricted to in the address range of 172.120.40.0/24. 
Packets from devices in the address range of 172.120.40.0/24 should be passed on VLAN 20. 
Packets from devices in any other address range should be dropped on VLAN 20. Filtering should be implemented as close to the server farm as possible. 
The Radius server and application servers will be installed at a future date. You have been tasked with implementing the above access control as a pre-condition to installing the servers. You must use the available IOS switch features.