19.5.6 Lab – Configure a Site-to-Site VPN Answers

Recommend

Network Security 1.0
Final Exam Answers
This Chapters 18 - 19
Chapters 18 - 19 Exam Answers	Online Test
Next Chapters 20 - 22
Chapters 20 - 22 Exam Answers	Online Test
Network Security Packet Tracer Activity Files Answers
19.5.5 Packet Tracer – Configure and Verify a Site-to-Site IPsec VPN Answers
Network Security Student Lab Source Files Answers
19.5.6 Lab – Configure a Site-to-Site VPN Answers

Lab – Configure a Site-to-Site VPN (Answers Version)

Answers Note: Red font color or gray highlights indicate text that appears in the instructor copy only.

Topology

Addressing Table

Device	Interface	IP Address	Subnet Mask	Default Gateway	Switch Port
R1	G0/0/1	192.168.1.1	255.255.255.0	N/A	S1 F0/5
R1	G0/0/0	10.1.1.1	255.255.255.252	N/A	N/A
R2	G0/0/0	10.1.1.2	255.255.255.252	N/A	N/A
R2	G0/0/1	10.2.2.2	255.255.255.252	N/A	N/A
R3	G0/0/1	192.168.3.1	255.255.255.0	N/A	S3 F0/5
R3	G0/0/0	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 F0/6
PC-C	NIC	192.168.3.3	255.255.255.0	192.168.3.1	S3 F0/18

Blank Line, No additional information

Objectives

Part 1: Configure Basic Device Settings

Configure hostnames, interface IP addresses, and access passwords.

Configure the OSPF 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.

Background / Scenario

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 of 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 will build and configure a multi-router network, use Cisco IOS to configure a site-to-site IPsec VPN, and then test the VPN. The IPsec VPN tunnel is from R1 to 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 and protecting and authenticating IP packets between participating IPsec devices (peers), such as Cisco routers.

Note: The routers used with hands-on labs are Cisco 4221 with Cisco IOS XE Release 16.9.6 (universalk9 image). The switches used in the labs are Cisco Catalyst 2960+ with Cisco IOS Release 15.2(7) (lanbasek9 image). Other routers, switches, and Cisco IOS versions can be used. Depending on the model and Cisco IOS version, the commands available and the output produced might vary from what is shown in the labs. Refer to the Router Interface Summary Table at the end of the lab for the correct interface identifiers.

Note: Before you begin, ensure that the routers and the switches have been erased and have no startup configurations.

Required Resources

3 Routers (Cisco 4221 with Cisco XE Release 16.9.6 universal image or comparable with a Security Technology Package license)

2 Switches (Cisco 2960+ with Cisco IOS Release 15.2(7) lanbasek9 image or comparable)

2 PCs (Windows OS with a terminal emulation program, such as PuTTY or Tera Term installed)

Console cables to configure Cisco networking devices

Ethernet cables as shown in the topology

Answers 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 of this lab is to configure a site-to-site VPN between two routers using the Cisco IOS CLI. R1 and R3 are on separate networks and communicate through R2, which simulates an ISP. The routers in this lab are configured with OSPF, 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 configures R1 and the other person configures R3.

Although switches are shown in the topology, students can omit the switches and use crossover cables between the PCs and R1 and R3.

The running configurations for all three routers are captured after Part 1 of the lab is completed. The running configurations for R1 and R3 from Part 2 are also captured. All configurations are found at the end of the lab.

Part 1:Configure Basic Device Settings

In Part 1, you will 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 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 as shown in the topology diagram and cable as necessary.

Step 2:Configure basic settings for each router.

Configure hostnames, as shown in the topology.
Configure the interface IP addresses, as shown in the Addressing Table.

Step 3:Disable DNS lookup.

Disable DNS lookup to prevent the router from attempting to translate incorrectly entered commands.

R1(config)# no ip domain lookup

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

On R1, use the following commands:

R1(config)# router ospf 101

R1(config-router)# network 192.168.1.0 0.0.0.255 area 0

R1(config-router)# network 10.1.1.0 0.0.0.3 area 0

On R2, use the following commands:

R2(config)# router ospf 101

R2(config-router)# network 10.1.1.0 0.0.0.3 area 0

R2(config-router)# network 10.2.2.0 0.0.0.3 area 0

On R3, use the following commands:

R3(config)# router ospf 101

R3(config-router)# network 192.168.3.0 0.0.0.255 area 0

R3(config-router)# network 10.2.2.0 0.0.0.3 area 0

Step 5:Configure PC host IP settings.

Configure a static IP address, subnet mask, and default gateway for PC-A, as shown in the IP Addressing Table.
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.

Ping from R1 to the R3 G0/0/1 interface at IP address 192.168.3.1.

If the pings are unsuccessful, troubleshoot the basic device configurations before continuing.

Ping from PC-A on the R1 LAN to PC-C on the R3 LAN.

If the pings are unsuccessful, troubleshoot the basic device configurations before continuing.

Note: If you can ping from PC-A to PC-C, you have demonstrated that the OSPF 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 and encrypt passwords.

Note: Passwords in this task 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.

Configure the same settings for R1 and R3.

Configure a minimum password length.

Use the security passwords command to set a minimum password length of 10 characters.

R1(config)# security passwords min-length 10

Configure the enable secret password on both routers with a password of cisco12345. Use the type 9 (SCRYPT) hashing algorithm.

R1(config)# enable algorithm-type scrypt secret cisco12345

Create a local admin01 account using admin01pass for the password. Use the type 9 (SCRYPT) hashing algorithm.

R1(config)# username admin01 algorithm-type scrypt secret admin01pass

Step 8:Configure the console line.

Configure the console to use the local database for login. For additional security, configure the line to log out after five minutes of inactivity. Issue the logging synchronous command to prevent console messages from interrupting command entry.

R1(config)# line console 0

R1(config-line)# login local

R1(config-line)# exec-timeout 5 0

R1(config-line)# logging synchronous

Step 9:Configure SSH Server.

Configure a domain name netsec.com.

R1(config)# ip domain-name netsec.com

Configure the RSA keys with 2048 for the number of modulus bits.

R1(config)# crypto key generate rsa general-keys modulus 2048

Issue the command to force the use of SSH version 2.

R1(config)# ip ssh version 2

Configure the vty lines on R1 and R3 to use the local database for login. Remote access to the routers should only be allowed using SSH. Configure the vty lines to logout after five minutes of inactivity.

R1(config)# line vty 0 4

R1(config-line)# login local

R1(config-line)# exec-timeout 5 0

R1(config-line)# transport input ssh

Step 10:Save the basic running configuration for all three routers.

Save the running configuration to the startup configuration from the privileged EXEC mode prompt on R1, R2, and R3.

R1# copy running-config startup-config

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

In Part 2 of this lab, you will 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 will then review and test the resulting configuration.

Note: Because no tunnel is yet in place, PC-A should still be able to ping PC-C. If not, troubleshoot the basic device configurations before continuing.

Task 1:Configure IPsec VPN Settings on R1 and R3.

Step 1:Enable IKE policies on R1 and R3.

IPsec is an open framework that allows for the exchange of security protocols as new technologies, and encryption algorithms as they are developed.

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

Implement Internet Key Exchange (IKE) parameters

Implement IPsec parameters

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, you can enable it with the crypto isakmp enable command. Use this command to verify that the router IOS supports IKE and that it is enabled.

R1(config)# crypto isakmp enable

R3(config)# crypto isakmp enable

Note: If you cannot execute this command on the router, you must upgrade to the IOS image that includes the Cisco cryptographic services.

Establish an ISAKMP policy and view the available options.

To allow IKE Phase 1 negotiation, you must create an ISAKMP policy and configure a peer association for that ISAKMP policy. An ISAKMP policy defines the authentication and encryption algorithms and the 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 global configuration mode command on R1 for policy 10.

R1(config)# crypto isakmp policy 10

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

R1(config-isakmp)# ?

ISAKMP commands:

authenticationSet authentication method for protection suite

defaultSet a command to its defaults

encryptionSet encryption algorithm for protection suite

exitExit from ISAKMP protection suite configuration mode

groupSet the Diffie-Hellman group

hashSet hash algorithm for protection suite

lifetimeSet lifetime for ISAKMP security association

noNegate a command or set its defaults

Step 2:Configure the IKE Phase 1 ISAKMP policy 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 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.

Configure an ISAKMP policy with a priority of 10. Use pre-shared key as the authentication type, aes 256 for the encryption algorithm, sha as the hash algorithm, and the Diffie-Hellman group 24 key exchange. Give the policy a lifetime of 3600 seconds (one hour).

Note: 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. Ensure that the same changes are made on R3 in order to be in sync.

R1(config)# crypto isakmp policy 10

R1(config-isakmp)# hash sha

R1(config-isakmp)# authentication pre-share

R1(config-isakmp)# group 24

R1(config-isakmp)# lifetime 3600

R1(config-isakmp)# encryption aes 256

R1(config-isakmp)# end

Configure the same policy on R3.

R3(config)# crypto isakmp policy 10

R3(config-isakmp)# hash sha

R3(config-isakmp)# authentication pre-share

R3(config-isakmp)# group 24

R3(config-isakmp)# lifetime 3600

R3(config-isakmp)# encryption aes 256

R3(config-isakmp)# end

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

R1# show crypto isakmp policy

Global IKE policy

Protection suite of priority 10

encryption algorithm:AES – Advanced Encryption Standard (256 bit keys).

hash algorithm:Secure Hash Standard

authentication method:Pre-Shared Key

Diffie-Hellman group:#24 (2048 bit, 256 bit subgroup)

lifetime:3600 seconds, no volume limit

Step 3:Configure pre-shared keys.

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

Type your answers here.

The IP addresses should be R1 G0/0/0 IP address 10.1.1.1 and R3 G0/0/0 IP address 10.2.2.1. These are the addresses that are used to send normal traffic between R1 and R3.

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. Production networks should use a complex key. This command points to the remote peer R3 G0/0/0 IP address.

R1(config)# crypto isakmp key cisco123 address 10.2.2.1

Configure the pre-shared key cisco123 on router R3. The command for R3 points to the R1 S0/0/0 IP address.

R3(config)# crypto isakmp key cisco123 address 10.1.1.1

Step 4:Configure the IPsec transform set and lifetime.

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 command where tag is a name configured by the administrator. Use ? to see which parameters are available.

R1(config)# crypto ipsec transform-set R1-R3 ?

ah-md5-hmacAH-HMAC-MD5 transform

ah-sha-hmacAH-HMAC-SHA transform

ah-sha256-hmacAH-HMAC-SHA256 transform

ah-sha384-hmacAH-HMAC-SHA384 transform

ah-sha512-hmacAH-HMAC-SHA512 transform

esp-192-aesESP transform using AES cipher (192 bits)

esp-256-aesESP transform using AES cipher (256 bits)

esp-3desESP transform using 3DES(EDE) cipher (168 bits)

esp-aesESP transform using AES cipher

esp-desESP transform using DES cipher (56 bits)

esp-gcmESP transform using GCM cipher

esp-gmacESP transform using GMAC cipher

esp-md5-hmacESP transform using HMAC-MD5 auth

esp-nullESP transform w/o cipher

esp-sealESP transform using SEAL cipher (160 bits)

esp-sha-hmacESP transform using HMAC-SHA auth

esp-sha256-hmacESP transform using HMAC-SHA256 auth

esp-sha384-hmacESP transform using HMAC-SHA384 auth

esp-sha512-hmacESP transform using HMAC-SHA512 auth

On R1 and R3, create a transform set with tag R1-R3 and use an ESP transform with an AES 256 cipher with ESP and the SHA hash function. The transform sets must match on both ends of the VPN.

R1(config)# crypto ipsec transform-set 50 esp-aes 256 esp-sha-hmac

R1(cfg-crypto-trans)# exit

R3(config)# crypto ipsec transform-set 50 esp-aes 256 esp-sha-hmac

R3(cfg-crypto-trans)# exit

What is the function of the IPsec transform set?

Type your answers here.

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.

You can also change the IPsec security association lifetime from the default of 3600 seconds. On R1 and R3, set the IPsec security association lifetime to 30 minutes, or 1800 seconds.

R1(config)# crypto ipsec security-association lifetime seconds 1800

R3(config)# crypto ipsec security-association lifetime seconds 1800

Step 5:Define interesting traffic.

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 the IPsec access list is not dropped. It is sent unencrypted. Also, like any other access list, there is an implicit deny at the end, which 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 unencrypted.

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

Configure the IPsec VPN interesting traffic ACL on R1.

R1(config)# access-list 101 permit ip 192.168.1.0 0.0.0.255 192.168.3.0 0.0.0.255

Configure the IPsec VPN interesting traffic ACL on R3.

R3(config)# access-list 101 permit ip 192.168.3.0 0.0.0.255 192.168.1.0 0.0.0.255

Question:

Does IPsec evaluate whether the access lists are mirrored as a requirement to negotiate its security association?

Type your answers here.

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 6: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.

To create a crypto map, use crypto map <name> <sequence-num> <type> command in global configuration mode to enter 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 crypto map configuration mode on R1. Use a type of ipsec-isakmp, which means IKE is used to establish IPsec security associations.

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

R1(config)# crypto map CMAP 10 ipsec-isakmp

% NOTE: This new crypto map will remain disabled until a peer

and a valid access list have been configured.

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

R1(config-crypto-map)# match address 101

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

R1(config-crypto-map)# set ?

identityIdentity restriction.

ipInterface Internet Protocol config commands

isakmp-profileSpecify isakmp Profile

natSet NAT translation

peerAllowed Encryption/Decryption peer.

pfsSpecify pfs settings

reverse-routeReverse Route Injection.

security-associationSecurity association parameters

transform-setSpecify list of transform sets in priority order

Setting a peer IP or hostname is required. Set it to R3’s remote VPN endpoint interface using the following command.

R1(config-crypto-map)# set peer 10.2.2.1

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

R1(config-crypto-map)# set pfs group24

R1(config-crypto-map)# set transform-set R1-R3

R1(config-crypto-map)# set security-association lifetime seconds 900

R1(config-crypto-map)# exit

Create a mirrored matching crypto map on R3.

R3(config)# crypto map CMAP 10 ipsec-isakmp

R3(config-crypto-map)# match address 101

R3(config-crypto-map)# set peer 10.1.1.1

R3(config-crypto-map)# set pfs group24

R3(config-crypto-map)# set transform-set R1-R3

R3(config-crypto-map)# set security-association lifetime seconds 900

R3(config-crypto-map)# exit

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

Note: . The router generates a notification that crypto is now on. However, the SAs are not established until the crypto map has been activated by interesting traffic

R1(config)# interface G0/0/0

R1(config-if)# crypto map CMAP

*Jan 28 04:09:09.150: %CRYPTO-6-ISAKMP_ON_OFF: ISAKMP is ON

R1(config)# end

R3(config)# interface G0/0/1

R3(config-if)# crypto map CMAP

*Jan 28 04:10:54.138: %CRYPTO-6-ISAKMP_ON_OFF: ISAKMP is ON

R3(config)# end

Task 2:Verify the Site-to-Site IPsec VPN Configuration.