CCNA RSE Lab: 5.2.2.9 Configuring Switch Security Features

CCNA RSE Lab: 5.2.2.9 Configuring Switch Security Features

Topology

Addressing Table

Device Interface IP Address Subnet Mask Default Gateway
R1 G0/1 172.16.99.1 255.255.255.0 N/A
S1 VLAN 99 172.16.99.11 255.255.255.0 172.16.99.1
PC-A NIC 1 72.16.99.3 255.255.255.0 172.16.99.1

Objectives
Part 1: Set up the Topology and Initialize Devices
Part 2: Configure Basic Device Settings and Verify Connectivity

Part 3: Configure and Verify SSH Access on S1

  • Configure SSH access.
  • Modify SSH parameters.
  • Verify the SSH configuration.

Part 4: Configure and Verify Security Features on S1

  • Configure and verify general security features.
  • Configure and verify port security.

Background / Scenario
It is quite common to lock down access and install strong security features on PCs and servers. It is important that your network infrastructure devices, such as switches and routers, are also configured with security features.

In this lab, you will follow some best practices for configuring security features on LAN switches. You will only allow SSH and secure HTTPS sessions. You will also configure and verify port security to lock out any device with a MAC address not recognized by the switch.

Note: The router used with CCNA hands-on labs is a Cisco 1 941 Integrated Services Router (ISR) with Cisco IOS Release 1 5.2(4)M3 (universalk9 image). The switch used is a Cisco Catalyst 2960 with Cisco IOS Release 1 5.0(2) (lanbasek9 image). Other routers, switches, and Cisco IOS versions can be used. Depending on the model and Cisco IOS version, the commands available and output produced might vary from what is

shown in this lab. Refer to the Router Interface Summary Table at the end of this lab for the correct interface identifiers.

Note: Make sure that the router and switch have been erased and have no startup configurations. If you are unsure, contact your instructor or refer to the previous lab for the procedures to initialize and reload devices.

Instructor Note: Refer to the Instructor Lab Manual for the procedures to initialize and reload devices.

Required Resources

  • 1 Router (Cisco 1941 with Cisco IOS Release 15.2(4)M3 universal image or comparable)
  • 1 Switch (Cisco 2960 with Cisco IOS Release 15.0(2) lanbasek9 image or comparable)
  • 1 PC (Windows 7, Vista, or XP with terminal emulation program, such as Tera Term)
  • 1 Console cable to configure the Cisco IOS devices via the console ports
  • 2 Ethernet cables as shown in the topology
Part 1: Set Up the Topology and Initialize Devices

In Part 1 , you will set up the network topology and clear any configurations if necessary.

Step 1: Cable the network as shown in the topology.
Step 2: Initialize and reload the router and switch.
If configuration files were previously saved on the router or switch, initialize and reload these devices back to their default configurations.

Part 2: Configure Basic Device Settings and Verify Connectivity

In Part 2, you will configure basic settings on the router, switch, and PC. Refer to the Topology and Addressing Table at the beginning of this lab for device names and address information.

Step 1: Configure an IP address on PC-A.
Refer to the Addressing Table for the IP Address information.

Step 2: Configure basic settings on R1 .
a. Console into R1 and enter global configuration mode.
b. Copy the following basic configuration and paste it to running-configuration on R1 .

c. Save the running configuration to startup configuration.

Step 3: Configure basic settings on S1 .
a. Console into S1 and enter global configuration mode.
b. Copy the following basic configuration and paste it to running-configuration on S1 .

c. Create VLAN 99 on the switch and name it Management.

d. Configure the VLAN 99 management interface IP address, as shown in the Addressing Table, and enable the interface.

e. Issue the show vlan command on S1.

What is the status of VLAN 99? ______________________ Active

f. Issue the show ip interface brief command on S1.

What is the status and protocol for management interface VLAN 99?
Status is up, and protocol is down.

Why is the protocol down, even though you issued the no shutdown command for interface VLAN 99?
No physical ports on the switch have been assigned to VLAN 99.

g. Assign ports F0/5 and F0/6 to VLAN 99 on the switch.

h. Save the running configuration to startup configuration.

i. Issue the show ip interface brief command on S1. What is the status and protocol showing for interface

VLAN 99? _______________________________________________ Up and up

Note: There may be a delay while the port states converge.

Step 4: Verify connectivity between devices.
a. From PC-A, ping the default gateway address on R1. Were your pings successful? ______________ Yes
b. From PC-A, ping the management address of S1. Were your pings successful? ______________ Yes
c. From S1, ping the default gateway address on R1. Were your pings successful? ______________ Yes
d. From PC-A, open a web browser and go to http://172.16.99.11 . If you are prompted for a username and password, leave the username blank and use class for the password. If you are prompted for a secured connection, answer No. Were you able to access the web interface on S1? ______________ Yes

e. Close the browser.

Note: The non-secure web interface (HTTP server) on a Cisco 2960 switch is enabled by default. A common security measure is to disable this service, as described in Part 4.

Part 3: Configure and Verify SSH Access on S1

Step 1: Configure SSH access on S1.
a. Enable SSH on S1. From global configuration mode, create a domain name of CCNA-Lab.com.

b. Create a local user database entry for use when connecting to the switch via SSH. The user should have administrative level access.

Note: The password used here is NOT a strong password. It is merely being used for lab purposes.

S1(config)# username admin privilege 15 secret sshadmin

c. Configure the transport input for the vty lines to allow SSH connections only, and use the local database for authentication.

d. Generate an RSA crypto key using a modulus of 1024 bits.

e. Verify the SSH configuration.

What version of SSH is the switch using? _______________________ 1.99
How many authentication attempts does SSH allow? _______________________ 3
What is the default timeout setting for SSH? _______________________ 120 seconds

Step 2: Modify the SSH configuration on S1.
Modify the default SSH configuration.

How many authentication attempts does SSH allow? _______________________ 2
What is the timeout setting for SSH? _______________________ 75 seconds

Step 3: Verify the SSH configuration on S1.
a. Using the SSH client software on PC-A (such as Tera Term), open an SSH connection to S1. If you receive a message on your SSH client regarding the host key, accept it. Log in with admin for username and sshadmin for the password.

Was the connection successful? _________________________ Yes

What prompt was displayed on S1? Why?
S1 is showing the prompt at privileged EXEC mode because the privilege 15 option was used when configuring username and password

b. Type exit to end the SSH session on S1.

Part 4: Configure and Verify Security Features on S1

In Part 4, you will shut down unused ports, turn off certain services running on the switch, and configure port security based on MAC addresses. Switches can be subject to MAC address table overflow attacks, MAC spoofing attacks, and unauthorized connections to switch ports. You will configure port security to limit the number of MAC addresses that can be learned on a switch port and disable the port if that number is exceeded.

Step 1: Configure general security features on S1.
a. Change the message of the day (MOTD) banner on S1 to, “Unauthorized access is strictly prohibited. Violators will be prosecuted to the full extent of the law.”

b. Issue a show ip interface brief command on S1 . What physical ports are up? Ports F0/5 and F0/6

c. Shut down all unused physical ports on the switch. Use the interface range command.

d. Issue the show ip interface brief command on S1. What is the status of ports F0/1 to F0/4?
Administratively down.

e. Issue the show ip http server status command.

What is the HTTP server status? ___________________________ Enabled
What server port is it using? ___________________________ 80
What is the HTTP secure server status? ___________________________ Enabled
What secure server port is it using? ___________________________ 443

f. HTTP sessions send everything in plain text. You will disable the HTTP service running on S1.

S1(config)# no ip http server

g. From PC-A, open a web browser and go to http://172.16.99.11 . What was your result?
The web page could not open. HTTP connections are now refused by S1.

h. From PC-A, open a web browser and go to https://172.16.99.11 . Accept the certificate. Log in with no

username and a password of class. What was your result?
Secure web session was successful.

i. Close the web browser.

Step 2: Configure and verify port security on S1.
a. Record the R1 G0/1 MAC address. From the R1 CLI, use the show interface g0/1 command and record the MAC address of the interface.

What is the MAC address of the R1 G0/1 interface?
____________________________________________________________________________________
In the example above, it is 30f7.0da3.1821

b. From the S1 CLI, issue a show mac address-table command from privileged EXEC mode. Find the dynamic entries for ports F0/5 and F0/6. Record them below.

c. Configure basic port security.

Note: This procedure would normally be performed on all access ports on the switch. F0/5 is shown here as an example.

1) From the S1 CLI, enter interface configuration mode for the port that connects to R1.
S1(config)# interface f0/5

2) Shut down the port.
S1(config-if)# shutdown

3) Enable port security on F0/5.
S1(config-if)# switchport port-security

Note: Entering the switchport port-security command sets the maximum MAC addresses to 1 and the violation action to shutdown. The switchport port-security maximum and switchport port-security violation commands can be used to change the default behavior.

4) Configure a static entry for the MAC address of R1 G0/1 interface recorded in Step 2a.

Note: Optionally, you can use the switchport port-security mac-address sticky command to add all the secure MAC addresses that are dynamically learned on a port (up to the maximum set) to the switch running configuration. 5) Enable the switch port.

d. Verify port security on S1 F0/5 by issuing a show port-security interface command.

What is the port status of F0/5?
The status is Secure-up, which indicates that the port is secure, but the status and protocol are up.

e. From R1 command prompt, ping PC-A to verify connectivity.

f. You will now violate security by changing the MAC address on the router interface. Enter interface configuration mode for G0/1 and shut it down.

g. Configure a new MAC address for the interface, using aaaa.bbbb.cccc as the address.

h. If possible, have a console connection open on S1 at the same time that you do the next two steps. You will eventually see messages displayed on the console connection to S1 indicating a security violation. Enable the G0/1 interface on R1.

i. From R1 privileged EXEC mode, ping PC-A. Was the ping successful? Why or why not?
No, the F0/5 port on S1 is shut down because of the security violation.

j. On the switch, verify port security with the following commands.

k. On the router, shut down the G0/1 interface, remove the hard-coded MAC address from the router, and re-enable the G0/1 interface.

l. From R1, ping PC-A again at 172.16.99.3. Was the ping successful? _________________ No

m. On the switch, issue the show interface f0/5 command to determine the cause of ping failure. Record your findings. F0/5 port on S1 is still in an error disabled state.

n. Clear the S1 F0/5 error disabled status.

Note: There may be a delay while the port states converge.

o. Issue the show interface f0/5 command on S1 to verify F0/5 is no longer in error disabled mode.

p. From the R1 command prompt, ping PC-A again. The ping should be successful.

Reflection
1. Why would you enable port security on a switch?
It would help prevent unauthorized devices from accessing your network if they plugged into a switch on your network.

2. Why should unused ports on a switch be disabled?
One excellent reason is that a user could not connect a device to the switch on an unused port and access the LAN.

Router Interface Summary Table

Router Interface Summary

Router Model Ethernet Interface #1 Ethernet Interface #2 Serial Interface #1 Serial Interface #2
1800 Fast Ethernet 0/0
(F0/0)
Fast Ethernet 0/1
(F0/1)
Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)
1900 Gigabit Ethernet 0/0
(G0/0)
Gigabit Ethernet 0/1
(G0/1)
Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)
2801 Fast Ethernet 0/0
(F0/0)
Fast Ethernet 0/1
(F0/1)
Serial 0/1 /0 (S0/1 /0) Serial 0/1 /1 (S0/1 /1)
2811 Fast Ethernet 0/0
(F0/0)
Fast Ethernet 0/1
(F0/1)
Serial 0/0/0 (S0/0/0) Serial 0/0/1 (S0/0/1)
2900 Gigabit Ethernet 0/0 (G0/0) Gigabit Ethernet 0/1 (G0/1) Serial 0/0/0(S0/0/0) Serial 0/0/1 (S0/0/1)
Note: To find out how the router is configured, look at the interfaces to identify the type of router and how many interfaces the router has. There is no way to effectively list all the combinations of configurations for each router class. This table includes identifiers for the possible combinations of Ethernet and Serial interfaces in the device. The table does not include any other type of interface, even though a specific router may contain one. An example of this might be an ISDN BRI interface. The string in parenthesis is the legal abbreviation that can be used in Cisco IOS commands to represent the interface.

Device Configs
Router R1

Switch S1

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