19.5.5 Packet Tracer – Configure and Verify a Site-to-Site IPsec VPN Answers Version
Topology
Addressing Table
Device | Interface | IP Address | Subnet Mask | Default Gateway | Switch Port |
---|---|---|---|---|---|
R1 | G0/0 | 192.168.1.1 | 255.255.255.0 | N/A | S1 F0/1 |
S0/0/0 (DCE) | 10.1.1.2 | 255.255.255.252 | N/A | N/A | |
R2 | G0/0 | 192.168.2.1 | 255.255.255.0 | N/A | S2 F0/2 |
S0/0/0 | 10.1.1.1 | 255.255.255.252 | N/A | N/A | |
S0/0/1 (DCE) | 10.2.2.1 | 255.255.255.252 | N/A | N/A | |
R3 | G0/0 | 192.168.3.1 | 255.255.255.0 | N/A | S3 F0/5 |
S0/0/1 | 10.2.2.2 | 255.255.255.252 | N/A | N/A | |
PC-A | NIC | 192.168.1.3 | 255.255.255.0 | 192.168.1.1 | S1 F0/2 |
PC-B | NIC | 192.168.2.3 | 255.255.255.0 | 192.168.2.1 | S2 F0/1 |
PC-C | NIC | 192.168.3.3 | 255.255.255.0 | 192.168.3.1 | S3 F0/18 |
Objectives
- Verify connectivity throughout the network.
- Configure R1 to support a site-to-site IPsec VPN with R3.
Background / Scenario
The network topology shows three routers. Your task is to configure R1 and R3 to support a site-to-site IPsec VPN when traffic flows between their respective LANs. 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 operates at the network layer and protects and authenticates IP packets between participating IPsec devices (peers), such as Cisco routers.
ISAKMP Phase 1 Policy Parameters
Parameters | R1 | R3 | |
---|---|---|---|
Key Distribution Method
Encryption Algorithm |
Manual or ISAKMP
DES, 3DES, or AES |
ISAKMP | ISAKMP |
AES 256 | AES 256 | ||
Hash Algorithm
Authentication Method Key Exchange |
MD5 or SHA-1
Pre-shared keys or RSA DH Group 1, 2, or 5 |
SHA-1 | SHA-1 |
pre-share | pre-share | ||
DH 5 | DH 5 | ||
IKE SA Lifetime
ISAKMP Key |
86400 seconds or less | 86400 | 86400 |
vpnpa55 | vpnpa55 |
Note: Bolded parameters are defaults. Only unbolded parameters have to be explicitly configured.
IPsec Phase 2 Policy Parameters
Parameters | R1 | R3 |
---|---|---|
Transform Set Name | VPN-SET | VPN-SET |
ESP Transform Encryption | esp-aes | esp-aes |
ESP Transform Authentication | esp-sha-hmac | esp-sha-hmac |
Peer IP Address | 10.2.2.2 | 10.1.1.2 |
Traffic to be Encrypted | access-list 110 (source 192.168.1.0 dest 192.168.3.0) |
access-list 110 (source 192.168.3.0 dest 192.168.1.0) |
Crypto Map Name | VPN-MAP | VPN-MAP |
SA Establishment | ipsec-isakmp | ipsec-isakmp |
The routers have been pre-configured with the following:
• Password for console line: ciscoconpa55
• Password for vty lines: ciscovtypa55
• Enable password: ciscoenpa55
• SSH username and password: SSHadmin / ciscosshpa55
• OSPF 101
Instructions
Part 1: Configure IPsec Parameters on R1
Step 1: Test connectivity.
Ping from PC-A to PC-C. The devices are all configured with routing. Therefore, the ping should succeed.
Step 2: Enable the Security Technology package.
a. On R1, issue the show version
command to view the Security Technology package license information.
b. If the Security Technology package has not been enabled, use the following command to enable the package.
R1(config)# license boot module c1900 technology-package securityk9
c. Accept the end-user license agreement.
d. Save the running-config and reload the router to enable the security license.
e. Use the show version
command again to verify that the securityk9 is listed under current Technology packages.
Step 3: Identify interesting traffic on R1.
Configure ACL 110 to identify the traffic from the LAN on R1 to the LAN on R3 as interesting. This interesting traffic will trigger the IPsec VPN to be implemented when there is traffic between the R1 to R3 LANs. All other traffic sourced from the LANs will not be encrypted. Because of the implicit deny all, there is no need to configure a deny ip any any statement.
R1(config)# access-list 110 permit ip 192.168.1.0 0.0.0.255 192.168.3.0 0.0.0.255
Step 4: Configure the IKE Phase 1 ISAKMP policy on R1.
Configure the crypto ISAKMP policy 10 properties on R1 along with the shared crypto key vpnpa55. Default values do not have to be configured. Therefore, only the encryption method, key exchange method, and DH method must be configured.
Note: The highest DH group currently supported by Packet Tracer is group 5. In a production network, you would configure at least DH 24.
R1(config)# crypto isakmp policy 10 R1(config-isakmp)# encryption aes 256 R1(config-isakmp)# authentication pre-share R1(config-isakmp)# group 5 R1(config-isakmp)# exit R1(config)# crypto isakmp key vpnpa55 address 10.2.2.2
Step 5: Configure the IKE Phase 2 IPsec policy on R1.
a. Create the transform-set VPN-SET to use esp-aes and esp-sha-hmac
.
R1(config)# crypto ipsec transform-set VPN-SET esp-aes esp-sha-hmac
b. Create the crypto map VPN-MAP that binds all of the Phase 2 parameters together. Use sequence number 10 and identify it as an ipsec-isakmp map.
R1(config)# crypto map VPN-MAP 10 ipsec-isakmp R1(config-crypto-map)# description VPN connection to R3 R1(config-crypto-map)# set peer 10.2.2.2 R1(config-crypto-map)# set transform-set VPN-SET R1(config-crypto-map)# match address 110 R1(config-crypto-map)# exit
Step 6: Configure the crypto map on the outgoing interface.
Bind the VPN-MAP crypto map to the outgoing Serial 0/0/0 interface.
R1(config)# interface s0/0/0 R1(config-if)# crypto map VPN-MAP
Part 2: Configure IPsec Parameters on R3
Step 1: Enable the Security Technology package.
a. On R3, issue the show version
command to verify that the Security Technology package license information has been enabled.
b. If the Security Technology package has not been enabled, enable the package and reload R3.
Step 2: Configure router R3 to support a site-to-site VPN with R1.
Configure reciprocating parameters on R3. Configure ACL 110 identifying the traffic from the LAN on R3 to the LAN on R1 as interesting.
R3(config)# access-list 110 permit ip 192.168.3.0 0.0.0.255 192.168.1.0 0.0.0.255
Step 3: Configure the IKE Phase 1 ISAKMP properties on R3.
Configure the crypto ISAKMP policy 10 properties on R3 along with the shared crypto key vpnpa55.
R3(config)# crypto isakmp policy 10 R3(config-isakmp)# encryption aes 256 R3(config-isakmp)# authentication pre-share R3(config-isakmp)# group 5 R3(config-isakmp)# exit R3(config)# crypto isakmp key vpnpa55 address 10.1.1.2
Step 4: Configure the IKE Phase 2 IPsec policy on R3.
a. Create the transform-set VPN-SET to use esp-aes and esp-sha-hmac.
R3(config)# crypto ipsec transform-set VPN-SET esp-aes esp-sha-hmac
b. Create the crypto map VPN-MAP that binds all of the Phase 2 parameters together. Use sequence number 10 and identify it as an ipsec-isakmp map.
R3(config)# crypto map VPN-MAP 10 ipsec-isakmp R3(config-crypto-map)# description VPN connection to R1 R3(config-crypto-map)# set peer 10.1.1.2 R3(config-crypto-map)# set transform-set VPN-SET R3(config-crypto-map)# match address 110 R3(config-crypto-map)# exit
Step 5: Configure the crypto map on the outgoing interface.
Bind the VPN-MAP crypto map to the outgoing Serial 0/0/1 interface. Note: This is not graded.
R3(config)# interface s0/0/1 R3(config-if)# crypto map VPN-MAP
Part 3: Verify the IPsec VPN
Step 1: Verify the tunnel prior to interesting traffic.
Issue the show crypto ipsec sa
command on R1. Notice that the number of packets encapsulated, encrypted, decapsulated, and decrypted are all set to 0.
Step 2: Create interesting traffic.
Ping PC-C from PC-A.
Step 3: Verify the tunnel after interesting traffic.
On R1, re-issue the show crypto ipsec sa
command. Notice that the number of packets is more than 0, which indicates that the IPsec VPN tunnel is working.
Step 4: Create uninteresting traffic.
Ping PC-B from PC-A. Note: Issuing a ping from router R1 to PC-C or R3 to PC-A is not interesting traffic.
Step 5: Verify the tunnel.
On R1, re-issue the show crypto ipsec sa
command. Notice that the number of packets has not changed, which verifies that uninteresting traffic is not encrypted.
Step 6: Check results.
Your completion percentage should be 100%. Click Check Results to see feedback and verification of which required components have been completed.
Answer Scripts
Router R1
config t license boot module c1900 technology-package securityk9 yes end copy running-config startup-config reload config t access-list 110 permit ip 192.168.1.0 0.0.0.255 192.168.3.0 0.0.0.255 crypto isakmp policy 10 encryption aes 256 authentication pre-share group 5 exit crypto isakmp key vpnpa55 address 10.2.2.2 crypto ipsec transform-set VPN-SET esp-aes esp-sha-hmac crypto map VPN-MAP 10 ipsec-isakmp description VPN connection to R3 set peer 10.2.2.2 set transform-set VPN-SET match address 110 exit interface S0/0/0 crypto map VPN-MAP
Router R3
config t access-list 110 permit ip 192.168.3.0 0.0.0.255 192.168.1.0 0.0.0.255 crypto isakmp policy 10 encryption aes 256 authentication pre-share group 5 exit crypto isakmp key vpnpa55 address 10.1.1.2 crypto ipsec transform-set VPN-SET esp-aes esp-sha-hmac crypto map VPN-MAP 10 ipsec-isakmp description VPN connection to R1 set peer 10.1.1.2 set transform-set VPN-SET match address 110 exit interface S0/0/1 crypto map VPN-MAP