CCNA Security Lab A: Configuring a Site-to-Site VPN Using Cisco IOS and SDM

CCNA Security Lab A: Configuring a Site-to-Site VPN Using Cisco IOS
and SDM

Topology
ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-top
IP Addressing Table

Device Interface          IP Address Subnet Mask Default Gateway Switch Port
R1 FA0/1                  192.168.1.1 255.255.255.0 N/A S1 FA0/5
S0/0/0 (DCE)      10.1.1.1 255.255.255.252 N/A N/A
R2 S0/0/0                  10.1.1.2 255.255.255.252 N/A N/A
S0/0/1 (DCE)      10.2.2.2 255.255.255.252 N/A N/A
R3 FA0/1                  192.168.3.1 255.255.255.0 N/A S3 FA0/5
S0/0/1                  10.2.2.1 255.255.255.252 N/A N/A
PC-A NIC                     192.168.1.3 255.255.255.0 192.168.1.1 S1 FA0/6
PC-C NIC                     192.168.3.3 255.255.255.0 192.168.3.1 S3 FA0/18

Objectives

Part 1: Basic Router Configuration

  • Configure host names, interface IP addresses, and access passwords.
  • Configure the EIGRP dynamic routing protocol.

Part 2: Configure a Site-to-Site VPN Using Cisco IOS

  • Configure IPsec VPN settings on R1 and R3
  • Verify site-to-site IPsec VPN configuration
  • Test IPsec VPN operation

Part 3: Configure a Site-to-Site VPN Using SDM

  • Configure IPsec VPN settings on R1
  • Create a mirror configuration for R3
  • Apply the mirror configuration to R3
  • Verify the configuration
  • Test the VPN configuration using SDM

Background
VPNs can provide a secure method of transmitting data over a public network, such as the Internet. VPN connections can help reduce the costs associated with leased lines. Site-to-Site VPNs typically provide a secure (IPsec or other) tunnel between a branch office and a central office. Another common implementation that uses VPN technology is remote access to a corporate office from a telecommuter location such as a small office or home office.

In this lab, you build a multi-router network and configure the routers and hosts. You use Cisco IOS and SDM to configure a site-to-site IPsec VPN and test it. The IPsec VPN tunnel is from router R1 to router R3 via R2. R2 acts as a pass-through and has no knowledge of the VPN. IPsec provides secure transmission of sensitive information over unprotected networks such as the Internet. IPsec acts at the network layer, protecting and authenticating IP packets between participating IPsec devices (peers), such as Cisco routers.

Note: The router commands and output in this lab are from a Cisco 1841 with Cisco IOS Release 12.4(20)T (Advanced IP image). Other routers and Cisco IOS versions can be used. See the Router Interface Summary table at the end of the lab to determine which interface identifiers to use based on the equipment in the lab. Depending on the router model and Cisco IOS version, the commands available and output produced might vary from what is shown in this lab.

Note: Make sure that the routers and the switches have been erased and have no startup configurations.

Instructor Note: Instructions for erasing switches and routers are provided in the Lab Manual, located on Academy Connection in the Tools section.

Required Resources

  • 3 routers with SDM 2.5 installed (Cisco 1841 with Cisco IOS Release 12.4(20)T1 or comparable)
  • 2 switches (Cisco 2960 or comparable)
  • PC-A (Windows XP or Vista)
  • PC-C (Windows XP or Vista)
  • Serial and Ethernet cables as shown in the topology
  • Rollover cables to configure the routers via the console

Instructor Notes:

This lab is divided into three parts. Each part can be administered individually or in combination with others as time permits. The main goal is to configure a site-to-site VPN between two routers, first using the Cisco IOS CLI and then using SDM. R1 and R3 are on separate networks and communicate through R2, which simulates an ISP. The routers in this lab are configured with EIGRP, although it is not typical for stub networks to communicate with an ISP using an interior routing protocol. You can also use static routes for basic (non-VPN) communication between R1 and R2 and between R1 and R3, if desired.

Students can work in teams of two for router configuration, one person configuring R1 and the other R3.

Although switches are shown in the topology, students can omit the switches and use crossover cables between the PCs and routers R1 and R3.
The running configs for all three routers are captured after Part 1 of the lab is completed.

The running configs for R1 and R3 from Part 2 and Part 3 are captured and listed separately. All configs are found at the end of the lab.

Part 1: Basic Router Configuration

In Part 1 of this lab, you set up the network topology and configure basic settings, such as the interface IP
addresses, dynamic routing, device access, and passwords.
Note: All tasks should be performed on routers R1, R2, and R3. The procedure for R1 is shown here as an example.

Step 1: Cable the network as shown in the topology.
Attach the devices shown in the topology diagram, and cable as necessary.

Step 2: Configure basic settings for each router.
a. Configure host names as shown in the topology.
b. Configure the interface IP addresses as shown in the IP addressing table.
c. Configure a clock rate for the serial router interfaces with a DCE serial cable attached.

Step 3. Disable DNS lookup.
To prevent the router from attempting to translate incorrectly entered commands, disable DNS lookup.

Step 4: Configure the EIGRP routing protocol on R1, R2, and R3.

a. On R1, use the following commands.

b. On R2, use the following commands.

c. On R3, use the following commands.

Step 5: Configure PC host IP settings.
a. Configure a static IP address, subnet mask, and default gateway for PC-A, as shown in the IP addressing table.

b. Configure a static IP address, subnet mask, and default gateway for PC-C, as shown in the IP addressing table.

Step 6: Verify basic network connectivity.
a. Ping from R1 to the R3 Fa0/1 interface at IP address 192.168.3.1. Were the results successful?
Yes. If the pings are not successful, troubleshoot the basic device configurations before continuing.

b. Ping from PC-A on the R1 LAN to PC-C on the R3 LAN. Were the results successful?
Yes. If the pings are not successful, troubleshoot the basic device configurations before continuing.

Note: If you can ping from PC-A to PC-C, you have demonstrated that the EIGRP routing protocol is configured and functioning correctly. If you cannot ping but the device interfaces are up and IP addresses are correct, use the show run and show ip route commands to help identify routing protocol-related problems.

Step 7: Configure a minimum password length.

 Note: Passwords in this lab are set to a minimum of 10 characters but are relatively simple for the benefit of performing the lab. More complex passwords are recommended in a production network. Use the security passwords command to set a minimum password length of 10 characters.

Step 8: Configure the basic console and vty lines.
a. Configure a console password and enable login for router R1. For additional security, the exectimeout command causes the line to log out after 5 minutes of inactivity. The logging synchronous command prevents console messages from interrupting command entry.

Note: To avoid repetitive logins during this lab, the exec-timeout can be set to 0 0, which prevents it from expiring. However, this is not considered a good security practice.

b. Configure the password on the vty lines for router R1.

c. Repeat these configurations on both R2 and R3.

Step 9: Encrypt clear text passwords.
a. Use the service password-encryption command to encrypt the console, aux, and vty passwords.

b. Issue the show run command. Can you read the console, aux, and vty passwords? Why or why not?
No, the passwords are now encrypted

c. Repeat this configuration on both R2 and R3.

Step 10: Save the basic running configuration for all three routers.
a. Save the running configuration to the startup configuration from the privileged EXEC prompt.

Step 11: Save the configuration on R1 and R3 for later restoration.
Use HyperTerminal or another means such as copy and paste to save the R1 and R3 running configurations from Part 1 of this lab and edit them so that they can be used to restore the routers in Part 3 of the lab to configure the VPN with SDM.

Note: When editing the captured running config text, remove all occurrences of “- – More – -.” Remove any commands that are not related to the items you configured in Part 1 of the lab, such as the Cisco IOS version number, no service pad, and so on. Many commands are entered automatically by the Cisco IOS software. Also replace the encrypted passwords with the correct ones specified previously and be sure to use the no shutdown command for interfaces that need to be enabled.

Part 2: Configure a Site-to-Site VPN with Cisco IOS

In Part 2 of this lab, you configure an IPsec VPN tunnel between R1 and R3 that passes through R2. You will
configure R1 and R3 using the Cisco IOS CLI. You then review and test the resulting configuration.

Task 1: Configure IPsec VPN Settings on R1 and R3

Step 1: Verify connectivity from the R1 LAN to the R3 LAN.
In this task, you verify that with no tunnel in place, the PC-A on the R1 LAN can ping the PC-C on R3 LAN.

a. From PC-A, ping the PC-C IP address of 192.168.3.3.
PC-A:\>ping 192.168.3.3

b. Were the results successful?
Yes. If the pings are not successful, troubleshoot the basic device configurations before continuing.

Step 2: Enable IKE policies on R1 and R3.
IPsec is an open framework that allows the exchange of security protocols as new technologies, such as encryption algorithms, are developed.

There are two central configuration elements to the implementation of an IPsec VPN:

  • Implement Internet Key Exchange (IKE) parameters
  • Implement IPsec parameters

a. Verify that IKE is supported and enabled.
IKE Phase 1 defines the key exchange method used to pass and validate IKE policies between peers. In IKE Phase 2, the peers exchange and match IPsec policies for the authentication and encryption of data traffic. IKE must be enabled for IPsec to function. IKE is enabled by default on IOS images with cryptographic feature sets. If it is disabled for some reason, you can enable it with the command crypto isakmp enable. Use this command to verify that the router IOS supports IKE and that it is enabled.

Note: If you cannot execute this command on the router, you need to upgrade the IOS image to one with a feature set that includes the Cisco cryptographic services.

b. Establish an Internet Security Association and Key Management Protocol (ISAKMP) policy and view the available options.
To allow IKE Phase 1 negotiation, you must create an ISAKMP policy and configure a peer association involving that ISAKMP policy. An ISAKMP policy defines the authentication and encryption algorithms and hash function used to send control traffic between the two VPN endpoints. When an ISAKMP security association has been accepted by the IKE peers, IKE Phase 1 has been completed. IKE Phase 2 parameters will be configured later. Issue the crypto isakmp policy number configuration command on R1 for policy 10.

c. View the various IKE parameters available using Cisco IOS help by typing a question mark (?).

Step 3: Configure ISAKMP policy parameters on R1 and R3.

Your choice of an encryption algorithm determines how confidential the control channel between the endpoints is. The hash algorithm controls data integrity, ensuring that the data received from a peer has not been tampered with in transit. The authentication type ensures that the packet was indeed sent and signed by the remote peer. The Diffie-Hellman group is used to create a secret key shared by the peers that has not been sent across the network.

a. Configure an authentication type of pre-shared keys. Use AES 256 encryption, SHA as your hash algorithm, and Diffie-Hellman group 5 key exchange for this IKE policy.

b. Give the policy a life time of 3600 seconds (one hour). Configure the same policy on R3. Older versions of Cisco IOS do not support AES 256 encryption and SHA as a hash algorithm. Substitute whatever encryption and hashing algorithm your router supports. Be sure the same changes are made on the other VPN endpoint so that they are in sync.

Note: You should be at the R1(config-isakmp)# at this point. The crypto isakmp policy 10 command is repeated below for clarity.

c. Verify the IKE policy with the show crypto isakmp policy command.

Step 4: Configure pre-shared keys.

a. Because pre-shared keys are used as the authentication method in the IKE policy, configure a key on each router that points to the other VPN endpoint. These keys must match for authentication to be successful. The global configuration command crypto isakmp key key-string address address is used to enter a pre-shared key. Use the IP address of the remote peer, the remote interface that the peer would use to route traffic to the local router.

Which IP addresses should you use to configure the IKE peers, given the topology diagram and IP addressing table?
The IP addresses should be R1 S0/0/0 IP address 10.1.1.1 and R3 S0/0/1 IP address 10.2.2.1 because these are the addresses that are used to send normal traffic between R1 and R3.

b. Each IP address that is used to configure the IKE peers is also referred to as the IP address of the remote VPN endpoint. Configure the pre-shared key of cisco123 on router R1 using the following command. Production networks should use a complex key. This command points to the remote peer R3 S0/0/1 IP address.

c. The command for R3 points to the R1 S0/0/0 IP address. Configure the pre-shared key on router R1 using the following command.

Step 5: Configure the IPsec transform set and life times.
a. The IPsec transform set is another crypto configuration parameter that routers negotiate to form a security association. To create an IPsec transform set, use the crypto ipsec transform-set tag parameters. Use ? to see which parameters are available.

b. On R1 and R3, create a transform set with tag 50 and use an Encapsulating Security Protocol (ESP) transform with an AES 256 cipher with ESP and the SHA hash function. The transform sets must match.

c. What is the function of the IPsec transform set? The IPsec transform set specifies the cryptographic algorithms and functions (transforms) that a router employs on the actual data packets sent through the IPsec tunnel. These algorithms include the encryption, encapsulation, authentication, and data integrity services that IPsec can apply.

d. You can also change the IPsec security association life times from the default of 3600 seconds or 4,608,000 kilobytes, whichever comes first. On R1 and R3, set the IPsec security association life time to 30 minutes, or 1800 seconds.

Step 6: Define interesting traffic.

a. To make use of the IPsec encryption with the VPN, it is necessary to define extended access lists to tell the router which traffic to encrypt. A packet that is permitted by an access list used for defining IPsec traffic is encrypted if the IPsec session is configured correctly. A packet that is denied by one of these access lists is not dropped, but sent unencrypted. Also, like any other access list, there is an implicit deny at the end, which, in this case, means the default action is to not encrypt traffic. If there is no IPsec security association correctly configured, no traffic is encrypted, and traffic is forwarded as unencrypted.

b. In this scenario, the traffic you want to encrypt is traffic going from R1 ’s Ethernet LAN to R3’s Ethernet LAN, or vice versa. These access lists are used outbound on the VPN endpoint interfaces and must mirror each other.

c. Configure the IPsec VPN interesting traffic ACL on R1.

d. Configure the IPsec VPN interesting traffic ACL on R3.

e. Does IPsec evaluate whether the access lists are mirrored as a requirement to negotiate its security association?
Yes, IPsec does evaluate whether access lists are mirrored. IPsec does not form a security association if the peers do not have mirrored access lists to select interesting traffic.

Step 7: Create and apply a crypto map.
A crypto map associates traffic that matches an access list to a peer and various IKE and IPsec settings. After the crypto map is created, it can be applied to one or more interfaces. The interfaces that it is applied to should be the ones facing the IPsec peer.

a. To create a crypto map, use the global configuration command crypto map name sequence-num type to enter the crypto map configuration mode for that sequence number. Multiple crypto map statements can belong to the same crypto map and are evaluated in ascending numerical order.

Enter the crypto map configuration mode on R1. Use a type of ipsec-isakmp, which means IKE is used to establish IPsec security associations.

b. Create the crypto map on R1, name it CMAP, and use 10 as the sequence number. A message will display after the command is issued.

c. Use the match address access-list command to specify which access list defines which traffic to encrypt.

d. To view the list of possible set commands that you can do in a crypto map, use the help function.

e. Setting a peer IP or host name is required, so set it to R3’s remote VPN endpoint interface using the following command.

f. Hard code the transform set to be used with this peer, using the set transform-set tag command. Set the perfect forwarding secrecy type using the set pfs type command, and also modify the default IPsec security association life time with the set security-association lifetime seconds seconds command.

g. Create a mirrored matching crypto map on R3.

h. The last step is applying the maps to interfaces. Note that the security associations (SAs) will not be established until the crypto map has been activated by interesting traffic. The router will generate a notification that crypto is now on.

i. Apply the crypto maps to the appropriate interfaces on R1 and R3.

Task 2: Verify Site-to-Site IPsec VPN Configuration
Step 1: Verify the IPsec configuration on R1 and R3.

a. Previously, you used the show crypto isakmp policy command to show the configured ISAKMP policies on the router. Similarly, the show crypto ipsec transform-set command displays the configured IPsec policies in the form of the transform sets.

b. Use the show crypto map command to display the crypto maps that will be applied to the router.

Note: The output of these show commands does not change if interesting traffic goes across the connection. You test various types of traffic in the next task.

Task 3: Verify IPsec VPN Operation

Step 1: Display isakmp security associations.
The show crypto isakmp sa command reveals that no IKE SAs exist yet. When interesting traffic is sent, this command output will change.

Step 2: Display IPsec security associations.
a. The show crypto ipsec sa command shows the unused SA between R1 and R3. Note the number of packets sent across and the lack of any security associations listed toward the bottom of the output. The output for R1 is shown here.

b. Why have no security associations (SAs) been negotiated? Because no interesting traffic has been identified, IPsec has not begun to negotiate a security association over which it will encrypt traffic.

Step 3: Generate some uninteresting test traffic and observe the results.
a. Ping from R1 to the R3 S0/0/1 interface IP address 10.2.2.1. Were the pings successful? Yes
b. Issue the show crypto isakmp sa command. Was an SA created between R1 and R3? No.
c. Ping from R1 to the R3 Fa01 interface IP address 192.168.3.1. Were the pings successful? Yes

d. Issue the show crypto isakmp sa command again. Was an SA created for these pings? Why or why not? No SA was created. The source address of both pings was the R1 S0/0/0 address of 10.1.1.1. In the first case, the destination address was 10.2.2.1. In the second case, the destination address was 192.168.3.1. This is not “interesting” traffic. The ACL 101 that is associated with th crypto map for R1 defines interesting traffic as IP packets from the 192.168.1.0/24 network to the 192.168.3.0/24 network.

e. Issue the command debug eigrp packets. You should see EIGRP hello packets passing between R1 and R3.

f. Turn off debugging with the no debug eigrp packets or undebug all command.

g. Issue the show crypto isakmp sa command again. Was an SA created between R1 and R3? Why or why not? No. This is router-to-router routing protocol traffic. The source and destination of these packets is not interesting, does not initiate the SA, and is not encrypted.

Step 4: Generate some interesting test traffic and observe the results.
a. Use an extended ping from R1 to the R3 Fa01 interface IP address 192.168.3.1. Extended ping allows you to control the source address of the packets. Respond as shown in the following example. Press enter to accept the defaults, except where a specific response is indicated.

b. Issue the show crypto isakmp sa command again.

c. Why was an SA created between R1 and R3 this time? The source was 192.168.1.1, and the destination was 192.168.3.1. This is interesting traffic based on the ACL 101 definition. An SA is established, and packets travel through the tunnel as encrypted traffic.

d. What are the endpoints of the IPsec VPN tunnel? Src: 10.1.1.1 (R1 S0/0/0), Dst: 10.2.2.1 (R3 S0/0/1)

e. Ping from PC-A to PC-C. Were the pings successful? Yes

 

f. Issue the show crypto ipsec sa command. How many packets have been transformed between R1 and R3? Nine, Five packets from the R1 to R3 pings, and four packets from the PC-A to R3 pings. One packet for each echo request. The number of packet may vary depending on how many pings have been issued and from where.

g. The previous example used pings to generate interesting traffic. What other types of traffic would result in an SA forming and tunnel establishment? Any traffic initiated from R1 with a source address in the 192.168.1.0/24 network and a destination address in the 192.168.3.0/24 network. On R3, interesting traffic is any traffic with a source address in the 192.168.3.0/24 network and a destination address in the 192.168.1.0/24 network. This includes FTP, HTTP, Telnet, and others.

Part 3: Configure a Site-to-Site IPsec VPN with SDM

In Part 3 of this lab, you configure an IPsec VPN tunnel between R1 and R3 that passes through R2. In Task 2, you configure R1 using Cisco SDM. In Task 3, you mirror those settings to R3 using SDM utilities. You then review and test the resulting configuration.

Task 1: Restore Router R1 and R3 to the Basic Settings
To avoid confusion as to what was entered in Part 2 of the lab, start by restoring R1 and R3 to the basic configuration as described in Part 1 of this lab.

Step 1: Erase and reload the router.
a. Connect to the router console, and enter privileged EXEC mode.
b. Erase the startup config and then issue the reload command to restart the router.

Step 2: Restore the basic configuration.
a. When the router restarts, enter privileged EXEC mode with the enable command, and then enter global config mode. Use the HyperTerminal Transfer > Send File function, copy and paste or use another method to load the basic startup config for R1 and R3 that was created and saved in Part 1 of this lab.

b. Save the running config to the startup config for R1 and R3 using the copy run start command.

c. Test connectivity by pinging from host PC-A to PC-C. If the pings are not successful, troubleshoot the router and PC configurations before continuing.

Task 2: Configure IPsec VPN Settings on R1 Using SDM

Step 1: Configure the enable secret password and HTTP router access prior to starting SDM.

a. From the CLI, configure the enable secret password for use with SDM on R1 and R3.

b. Enable the HTTP server on R1 and R3.

Step 2: Access SDM and set command delivery preferences.
a. Run the SDM application, or open a browser on PC-A and start SDM by entering the R1 IP address 192.168.1.1 in the address field.

Note: You might be prompted by Internet Explorer to allow ActiveX during several of these steps. Click Allow.

b. Log in with no username and the enable secret password cisco12345.

c. In the Authentication Required dialog box, leave the Username field blank and enter cisco12345 in the Password field. Click Yes.

d. If the IOS IPS login dialog displays, click the Cancel button to bypass this option.

e. Select Edit > Preferences to configure SDM to allow you to preview the commands before sending them to the router. In the User Preferences window, check the Preview commands before delivering to router check box and click OK.

Step 3: Start the SDM VPN wizard to configure R1.

a. Click the Configure button at the top of the SDM screen, and then click the VPN button. Select Siteto-Site VPN from the list of options. The default option is Create Site-to-Site VPN. Read through the description of this option.

b. What must you know to complete the configuration?
The remote device (R3 S0/0/1) IP address and the pre-shared key (cisco12345), which will be established in Task 2, Step 4.
ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-1

c. Click the Launch the selected task button to begin the SDM Site-to-Site VPN wizard.

d. On the initial Site-to-Site VPN wizard window, the Quick Setup option is selected by default. Click the View Details button to see what settings this option uses. What type of encryption does the default transform set use? ESP-3DES

e. From the initial Site-to-Site VPN wizard window, select the Step by Step wizard, and then click Next. Why would you use this option over the Quick setup option? So that you have more control over the VPN settings used.

Step 4: Configure basic VPN connection information settings.

a. From the VPN Connection Information window, select the interface for the connection, which should be R1 Serial0/0/0.

b. In the Peer Identity section, select Peer with static address and enter the IP address of remote peer R3 S0/0/1 (10.2.2.1).

c. In the Authentication section, click Pre-shared keys, and enter the pre-shared VPN key cisco12345. Re-enter the key for confirmation. This key is what protects the VPN and keeps it secure. When finished, your screen should look similar to the following. Once you have entered these settings correctly, click Next.

ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-2

Step 5: Configure IKE policy parameters.
IKE policies are used while setting up the control channel between the two VPN endpoints for key exchange. This is also referred to as the IKE secure association (SA). In contrast, the IPsec policy is used during IKE Phase II to negotiate an IPsec security association to pass target data traffic.

a. In the IKE Proposals window, a default policy proposal is displayed. You can use this one or create a new one. What function does this IKE proposal serve? The IKE proposal specifies the encryption algorithm, authentication algorithm, and key exchange method used by this router when negotiating a VPN connection with a remote router.

b. Click the Add button to create a new IKE policy.

c. Set up the security policy as shown in the Add IKE Policy dialog box below. These settings are matched later on R3. When finished, click OK to add the policy. Then click Next.

ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-3

d. Click the Help button to assist you with answering the following questions. What is the function of the encryption algorithm in the IKE policy? The encryption algorithm encrypts and decrypts the payload of the control packets that pass over the secure IKE channel.

e. What is the purpose of the hash function? The hash validates that the entire control packet has not been tampered with during transit. The hash also authenticates the remote peer as the origin of the packet via a secret key.

f. What function does the authentication method serve? Both endpoints verify that the IPsec traffic that
they have received is sent by the remote IPsec peer.

g. How is the Diffie-Hellman group in the IKE policy used? The Diffie-Hellman group is used by each of the endpoints to generate a shared secret key, which is never transmitted across the network. Each Diffie-Hellman group has an associated key length.

h. What event happens at the end of the IKE policy’s lifetime? IKE renegotiates the IKE association.

Step 6: Configure a transform set.
The transform set is the IPsec policy used to encrypt, hash, and authenticate packets that pass through the tunnel. The transform set is the IKE Phase 2 policy.

a. An SDM default transform set is displayed. Click the Add button to create a new transform set.

b. Set up the transform set as shown in the Transform Set dialog box below. These settings are matched later on R3. When finished, click OK to add the transform set. Then click Next.

ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-4

Step 7: Define interesting traffic.
You must define interesting traffic to be protected through the VPN tunnel. Interesting traffic will be defined through an access list when applied to the router. If you enter source and destination subnets, SDM generates the appropriate simple access list for you.

In the Traffic to protect window, enter the information as shown below. These are the opposite of the settings configured on R3 later in the lab. When finished, click Next.

ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-5

Step 8: Review the summary configuration and deliver commands to the router.
a. Review the summary of the Configuration window. It should look similar to the one below. Do not select the checkbox for Test VPN connectivity after configuring. This is done after configuring R3.

ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-6

b. In the Deliver Configuration to router window, select Save running config to router’s startup config and click the Deliver button. After the commands have been delivered, click OK. How many commands were delivered? 31 with SDM 2.5

Task 3: Create a Mirror Configuration for R3

Step 1: Use SDM on R1 to generate a mirror configuration for R3.
a. On R1, select VPN > Site-to-Site VPN and click the Edit Site-to-Site VPN tab. You should see the VPN configuration you just created on R1 listed. What is the description of the VPN? Tunnel to 10.2.2.1

b. What is the status of the VPN and why? Down. The IKE security association could not be established because the VPN peer R3 has not yet been configured. R3 must be configured with the appropriate VPN parameters, such as matching IKE proposals and IPsec policies and a mirrored access list, before the IKE and IPsec security associations will activate.

c. Select the VPN policy you just configured on R1 and click the Generate Mirror button in the lower right of the window. The Generate Mirror window displays the commands necessary to configure R3 as a VPN peer. Scroll through the window to see all the commands generated.
ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-7

d. The text at the top of the window states that the configuration generated should only be used as a guide for setting up a site-to-site VPN. What commands are missing to allow this crypto policy to function on R3? The commands to apply the crypto map to the S0/0/1 interface.

Hint: Look at the description entry following the crypto map SDM_CMAP_1 command.

Step 2: Save the configuration commands for R3.
a. Click the Save button to create a text file for use in the next task.
b. Save the commands to the desktop or other location and name it VPN-Mirror-Cfg-for-R3.txt.

Note: You can also copy the commands directly from the Generate Mirror window.

c. (Optional) Edit the file to remove the explanation text at the beginning and the description entry following the crypto map SDM_CMAP_1 command.

Task 4: Apply the Mirror Configuration to R3 and Verify the Configuration

Step 1: Access the R3 CLI and copy the mirror commands.

Note: You can also use SDM on R3 to create the appropriate VPN configuration, but copying and pasting the mirror commands generated from R1 is easier.

a. On R3, enter privileged EXEC mode and then global config mode.

b. Copy the commands from the text file into the R3 CLI.

Step 2: Apply the crypto map to the R3 S0/0/1 interface.

Step 3: Verify the VPN configuration on R3 using Cisco IOS.

a. Display the running config beginning with the first line that contains the string “0/0/1” to verify that the crypto map is applied to S0/0/1.

b. On R3, use the show crypto isakmp policy command to show the configured ISAKMP policies on the router. Note that the default SDM policy is also present.

c. In the above output, how many ISAKMP policies are there? Two, the SDM default with priority 1 and the one with priority 10, which was created during the SDM session with R1 and copied as part of the mirror configuration.

d. Issue the show crypto ipsec transform-set command to display the configured IPsec policies in the form of the transform sets.

e. Use the show crypto map command to display the crypto maps that will be applied to the router.

f. In the above output, the ISAKMP policy being used by the crypto map is the SDM default policy with sequence number priority 1, indicated by the number 1 in the first output line: Crypto Map “SDM_CMAP_1” 1 ipsec-isakmp. Why is it not using the one you created in the SDM session — the one shown with priority 10 in Step 3b above? The SDM crypto map config defaults to using the default ISAKMP policy.

g. (Optional) You can force the routers to use the more stringent policy that you created by changing the crypto map references in the R1 and R3 router configs as shown below. If this is done, the default  ISAKMP policy 1 can be removed from both routers.

Task 5: Test the VPN Configuration Using SDM on R1.

a. On R1, use SDM to test the IPsec VPN tunnel between the two routers. Select VPN > Site-to-Site
VPN and click the Edit Site-to-Site VPN tab.

b. From the Edit Site to Site VPN tab, select the VPN and click Test Tunnel.

c. When the VPN Troubleshooting window displays, click the Start button to have SDM start troubleshooting the tunnel.

d. When the SDM Warning window displays indicating that SDM will enable router debugs and generate some tunnel traffic, click Yes to continue.

e. In the next VPN Troubleshooting window, the IP address of the R1 Fa0/1 interface in the source network is displayed by default (192.168.1.1). Enter the IP address of the R3 Fa0/1 interface in the destination network field (192.168.3.1) and click   Continue to begin the debugging process.
ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-8

f. If the debug is successful and the tunnel is up, you should see the screen below. If the testing fails, SDM displays failure reasons and recommended actions. Click OK to remove the window.
ccna-security-lab-configuring-site-site-vpn-using-cisco-ios-sdm-9

g. You can save the report if desired; otherwise, click Close.

Note: If you want to reset the tunnel and test again, you can click the Clear Connection button from the Edit Suite-to-Site VPN window. This can also be accomplished at the CLI using the clear crypto session command.

h. Display the running config for R3 beginning with the first line that contains the string 0/0/1 to verify that the crypto map is applied to S0/0/1.

i. Issue the show crypto isakmp sa command on R3 to view the security association created.

j. Issue the show crypto ipsec sa command. How many packets have been transformed between

Task 6: Reflection
a. Would traffic on the Fast Ethernet link between PC-A and the R1 Fa0/0 interface be encrypted by the site-to-site IPsec VPN tunnel? Why or why not? No, this site-to-site VPN only encrypts from router R1 to R3. A sniffer could be used to see the traffic from PC-A to the R1 default gateway.

b. What are some factors to consider when configuring site-to-site IPsec VPNs using the manual CLI compared to using the SDM VPN wizard GUI?
Answers will vary but could include: Traditional CLI methods are time-consuming and prone to keystroke errors. They also require the administrator to have an extensive knowledge of IPsec VPNs and Cisco IOS command syntax. SDM gives the maximum flexibility and greatly simplifies IPsec VPN configuration. SDM also provides help and explanations on various technologies and settings available

Router Interface Summary Table

Router Interface Summary

Router Model Ethernet Interface
#1
Ethernet Interface
#2
Serial Interface
#1
Serial Interface
#2
1700 Fast Ethernet 0
(Fa0)
Fast Ethernet 1
(Fa1)
Serial 0 (S0) Serial 0/0/1
(S0/0/1)
1800 Fast Ethernet 0/0
(Fa0/0)
Fast Ethernet 0/1
(Fa0/1)
Serial 0/0/0
(S0/0/0)
Serial 0/0/1
(S0/0/1)
2600 Fast Ethernet 0/0
(Fa0/0)
Fast Ethernet 0/1
(Fa0/1)
Serial 0/0 (S0/0) Serial 0/1 (S0/1)
2800 Fast Ethernet 0/0
(Fa0/0)
Fast Ethernet 0/1
(Fa0/1)
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. Rather than list all 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 might contain one. For example, for an ISDN BRI interface, the string in parenthesis is the legal abbreviation that can be used in Cisco IOS commands to represent the interface.

Router Configs

Router R1 after Part 1

Router R2 after Part 1

Router R3 after Part 1

Router R1 after Part 2

Router R3 after Part 2

Router R1 after Part 3

Router R3 after Part 3

More Resources

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Prasanna

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