Cisco PIX Firewall and VPN Configuration Guide, Version 6.2 - Site-to-Site VPN Configuration Examples [Cisco PIX Firewall Software]

Table Of Contents

Site-to-Site VPN Configuration Examples

Using Pre-Shared Keys

Scenario Description

Configuring PIX Firewall 1 with VPN Tunneling

Configuring PIX Firewall 2 for VPN Tunneling

Using PIX Firewall with a VeriSign CA

Scenario Description

Configuring PIX Firewall 1 with a VeriSign CA

Configuring PIX Firewall 2 with a VeriSign CA

Using PIX Firewall with an In-House CA

Scenario Description

Configuring PIX Firewall 1 for an In-House CA

Configuring PIX Firewall 2 for an In-House CA

Using an Encrypted Tunnel to Obtain Certificates

Establishing a Tunnel Using a Pre-Shared Key

PIX Firewall 1 Configuration

PIX Firewall 2 Configuration

Establishing a Tunnel with a Certificate

PIX Firewall 1 Configuration

PIX Firewall 2 Configuration

Manual Configuration with NAT

PIX Firewall 1 Configuration

PIX Firewall 2 Configuration

Site-to-Site VPN Configuration Examples

A site-to-site VPN protects the network resources on your protected networks from unauthorized use by users on an unprotected network, such as the public Internet. The basic configuration for this type of implementation has been covered in Chapter 6, "Configuring IPSec and Certification Authorities." This chapter provides examples of the following site-to-site VPN configurations:

•Using Pre-Shared Keys

•Using PIX Firewall with a VeriSign CA

•Using PIX Firewall with an In-House CA

•Using an Encrypted Tunnel to Obtain Certificates

•Manual Configuration with NAT

Note Throughout the examples in this chapter, the local PIX Firewall unit is identified as PIX Firewall 1 while the remote unit is identified as PIX Firewall 2. This designation makes it easier to clarify the configuration required for each.

Using Pre-Shared Keys

This section describes an example configuration for using pre-shared keys. It contains the following topics:

•Scenario Description

•Configuring PIX Firewall 1 with VPN Tunneling

•Configuring PIX Firewall 2 for VPN Tunneling

Scenario Description

In the example illustrated in Figure 7-1, the intranets use unregistered addresses and are connected over the public Internet by a site-to-site VPN. In this scenario, NAT is required for connections to the public Internet. However, NAT is not required for traffic between the two intranets, which can be transmitted using a VPN tunnel over the public Internet.

Note If you do not need to do VPN tunneling for intranet traffic, you can use this example without the access-list or the nat 0 access-list commands. These commands disable NAT for traffic that matches the access list criteria.

If you have a limited number of registered IP addresses and you cannot use PAT, you can configure PIX Firewall to use NAT for connections to the public Internet, but avoid NAT for traffic between the two intranets. This configuration might also be useful if you were replacing a direct, leased-line connection between two intranets.

Figure 7-1 VPN Tunnel Network

The configuration shown for this example uses an access list to exclude traffic between the two intranets from NAT. The configuration assigns a global pool of registered IP addresses for use by NAT for all other traffic. By excluding intranet traffic from NAT, you need fewer registered IP addresses.

Configuring PIX Firewall 1 with VPN Tunneling

Follow these steps to configure PIX Firewall 1:

Step 1 Define a host name:
hostname NewYork
Step 2 Configure an ISAKMP policy:
isakmp enable outside
isakmp policy 9 authentication pre-share	
isakmp policy 9 encrypt des
Step 3 Configure a pre-shared key and associate with the peer:
crypto isakmp key cisco1234 address 209.165.200.229
Step 4 Configure the supported IPSec transforms:
crypto ipsec transform-set strong esp-des esp-sha-hmac
Step 5 Create an access list:
access-list 90 permit ip 192.168.12.0 255.255.255.0 10.0.0.0 255.0.0.0
This access list defines traffic from network 192.168.12.0 to 10.0.0.0. Both of these networks use unregistered addresses.

Note Steps 5 and 6 are not required if you want to enable NAT for all traffic.

Step 6 Exclude traffic between the intranets from NAT:
nat 0 access-list 90
This excludes traffic matching access list 90 from NAT. The nat 0 command is always processed before any other nat commands.

Step 7 Enable NAT for all other traffic:
nat (inside) 1 0 0
Step 8 Assign a pool of global addresses for NAT and PAT:
global (outside) 1 209.165.202.129-209.165.202.159
global (outside) 1 209.165.202.160
The pool of registered addresses are only used for connections to the public Internet.

Step 9 Define a crypto map:
crypto map toSanJose 20 ipsec-isakmp 
crypto map toSanJose 20 match address 90
crypto map toSanJose 20 set transform-set strong
crypto map toSanJose 20 set peer 209.165.200.229
Step 10 Apply the crypto map to the outside interface:
crypto map toSanJose interface outside
Step 11 Specify that IPSec traffic be implicitly trusted (permitted):
sysopt connection permit-ipsec
Example 7-1 lists the configuration for PIX Firewall 1.

Example 7-1 PIX Firewall 1 VPN Tunnel Configuration
nameif ethernet0 outside security0
nameif ethernet1 inside security100
interface ethernet0 auto
interface ethernet1 auto
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname NewYork
domain-name example.com
fixup protocol ftp 21
fixup protocol http 80
fixup protocol smtp 25
fixup protocol h323 1720
fixup protocol rsh 514
fixup protocol sqlnet 1521
names
pager lines 24
no logging on
mtu outside 1500
mtu inside 1500
ip address outside 209.165.201.8 255.255.255.224
ip address inside 192.168.12.1 255.255.255.0
no failover
failover ip address outside 0.0.0.0
failover ip address inside 0.0.0.0
arp timeout 14400
nat 0 access-list 90
access-list 90 permit ip 192.168.12.0 255.255.255.0 10.0.0.0 255.0.0.0
nat (inside) 1 0 0
global (outside) 1 209.165.202.129-209.165.202.159
global (outside) 1 209.165.202.160
no rip outside passive
no rip outside default
rip inside passive
no rip inside default
route outside 0.0.0.0 0.0.0.0 209.165.201.7 1
timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00
timeout rpc 0:10:00 h323 0:05:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
sysopt connection permit-ipsec
crypto ipsec transform-set strong esp-3des esp-sha-hmac
crypto map toSanJose 20 ipsec-isakmp
crypto map toSanJose 20 match address 90
crypto map toSanJose 20 set peer 209.165.200.229
crypto map toSanJose 20 set transform-set strong
crypto map toSanJose interface outside
isakmp enable outside
isakmp key cisco1234 address 209.165.200.229 netmask 255.255.255.255
isakmp policy 9 authentication pre-share
isakmp policy 9 encryption 3des
telnet timeout 5
terminal width 80
Note In this example, the following statements are not used when enabling NAT for all traffic:
nat 0 access-list 90
access-list 90 permit ip 192.168.12.0 255.255.255.0 10.0.0.0 255.0.0.0

Configuring PIX Firewall 2 for VPN Tunneling

Follow these steps to configure PIX Firewall 2:

Step 1 Define a host name:
hostname SanJose
Step 2 Define the domain name:
domain-name example.com
Step 3 Create a net static:
static (inside,outside) 10.0.0.0 10.0.0.0 netmask 255.0.0.0
Step 4 Configure the ISAKMP policy:
isakmp enable outside
isakmp policy 8 authentication pre-share	
isakmp policy 8 encryption 3des
Step 5 Configure a pre-shared key and associate it with the peer:
crypto isakmp key cisco1234 address 209.165.201.8
Step 6 Configure IPSec supported transforms:
crypto ipsec transform-set strong esp-3des esp-sha-hmac
Step 7 Create an access list:
access-list 80 permit ip 10.0.0.0 255.0.0.0 192.168.12.0 255.255.255.0
This access list defines traffic from network 10.0.0.0 to 192.168.12.0. Both of these networks use unregistered addresses.

Note Step 7 and Step 8 are not required if you want to enable NAT for all traffic.

Step 8 Exclude traffic between the intranets from NAT:
nat 0 access-list 80
This excludes traffic matching access list 80 from NAT. The nat 0 command is always processed before any other nat commands.

Step 9 Enable NAT for all other traffic:
nat (inside) 1 0 0
Step 10 Assign a pool of global addresses for NAT and PAT:
global (outside) 1 209.165.202.160-209.165.202.89
global (outside) 1 209.165.202.190
The pool of registered addresses are only used for connections to the public Internet.

Step 11 Define a crypto map:
crypto map newyork 10 ipsec-isakmp 
crypto map newyork 10 match address 80
crypto map newyork 10 set transform-set strong
crypto map newyork 10 set peer 209.165.201.8
Step 12 Apply the crypto map to an interface:
crypto map newyork interface outside
Step 13 Specify that IPSec traffic be implicitly trusted (permitted):
sysopt connection permit-ipsec
Example 7-2 lists the configuration for PIX Firewall 2.

Example 7-2 PIX Firewall 2 VPN Tunnel Configuration
nameif ethernet0 outside security0
nameif ethernet1 inside security100
nameif ethernet2 dmz security50
nameif ethernet3 perimeter security40
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname SanJose
domain-name example.com
fixup protocol ftp 21
fixup protocol http 80
fixup protocol smtp 25
fixup protocol h323 1720
fixup protocol rsh 514
fixup protocol sqlnet 1521
names
pager lines 24
no logging on
interface ethernet0 auto
interface ethernet1 auto
interface ethernet2 auto
interface ethernet3 auto
mtu outside 1500
mtu inside 1500
mtu dmz 1500
mtu perimeter 1500
ip address outside 209.165.200.229 255.255.255.224
ip address inside 10.0.0.1 255.0.0.0
ip address dmz 192.168.101.1 255.255.255.0
ip address perimeter 192.168.102.1 255.255.255.0
no failover
failover ip address outside 0.0.0.0
failover ip address inside 0.0.0.0
failover ip address dmz 0.0.0.0
failover ip address perimeter 0.0.0.0
arp timeout 14400
nat 0 access-list 80
access-list 80 permit ip 10.0.0.0 255.0.0.0 192.168.12.0 255.255.255.0
nat (inside) 1 0 0
global (outside) 1 209.165.202.160-209.165.202.89
global (outside) 1 209.165.202.190
no rip outside passive
no rip outside default
no rip inside passive
no rip inside default
no rip dmz passive
no rip dmz default
no rip perimeter passive
no rip perimeter default
route outside 0.0.0.0 0.0.0.0 209.165.200.228 1
timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00
timeout rpc 0:10:00 h323 0:05:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
sysopt connection permit-ipsec
crypto ipsec transform-set strong esp-3des esp-sha-hmac
crypto map newyork 10 ipsec-isakmp
crypto map newyork 10 match address 80
crypto map newyork 10 set peer 209.165.201.8
crypto map newyork 10 set transform-set strong
crypto map newyork interface outside
isakmp enable outside
isakmp key cisco1234 address 209.165.201.8 netmask 255.255.255.255
isakmp policy 8 authentication pre-share
isakmp policy 8 encryption 3des
telnet timeout 5
terminal width 80
Note In Example 7-2, the following statements are not used when enabling NAT for all traffic:
nat 0 access-list 80
access-list 80 permit ip 10.0.0.0 255.0.0.0 192.168.12.0 255.255.255.00

Using PIX Firewall with a VeriSign CA

This section provides configuration examples showing how to configure interoperability between two PIX Firewall units (PIX Firewall 1 and 2) for site-to-site VPN using the VeriSign CA server for device enrollment, certificate requests, and digital certificates for the IKE authentication. This section includes the following topics:

•Scenario Description

•Configuring PIX Firewall 1 with a VeriSign CA

•Configuring PIX Firewall 2 with a VeriSign CA

Scenario Description

The two VPN peers in the configuration examples are shown to be configured to enroll with VeriSign at the IP address of 209.165.202.130 and to obtain their CA certificates from this CA server. VeriSign is a public CA that issues its CA-signed certificates over the Internet. Once each peer obtains its CA-signed certificate, tunnels can be established between the two VPN peers using digital certificates as the authentication method used during IKE authentication. The peers dynamically authenticate each other using the digital certificates.

Note VeriSign's actual CA server address differs. The example CA server address is to be used for example purposes only.

For the general procedures to configure the PIX Firewall for a CA, see "Using Certification Authorities" in Chapter 6, "Configuring IPSec and Certification Authorities."

This section provides an example configuration for the specific network illustrated in Figure 7-2.

Figure 7-2 VPN Tunnel Network

Configuring PIX Firewall 1 with a VeriSign CA

Perform the following steps to configure PIX Firewall 1 to use a public CA:

Step 1 Define a host name:
hostname NewYork
Step 2 Define the domain name:
domain-name example.com
Step 3 Generate the PIX Firewall RSA key pair:
ca generate rsa key 512
This command is not stored in the configuration.

Step 4 Define VeriSign-related enrollment commands:
ca identity example.com 209.165.202.130
ca configure example.com ca 2 20 crloptional
These commands are stored in the configuration. "2" is the retry period, "20" is the retry count, and the crloptional option disables CRL checking.

Step 5 Authenticate the CA by obtaining its public key and its certificate:
ca authenticate example.com
This command is not stored in the configuration.

Step 6 Request signed certificates from your CA for your PIX Firewall's RSA key pair. Before entering this command, contact your CA administrator because they will have to authenticate your PIX Firewall manually before granting its certificate.
ca enroll example.com abcdef
"abcdef" is a challenge password. This can be anything. This command is not stored in the configuration.

Step 7 Verify that the enrollment process was successful using the show ca certificate command:
show ca certificate
Step 8 Save keys and certificates, and the CA commands (except those indicated) in Flash memory:
ca save all
write memory
Note Use the ca save all command any time you add, change, or delete ca commands in the configuration. This command is not stored in the configuration.

Step 9 Create a net static:
static (inside,outside) 192.168.12.0 192.168.12.0
Step 10 Configure an IKE policy:
isakmp enable outside
isakmp policy 8 auth rsa-sig
Step 11 Create a partial access list:
access-list 90 permit ip 192.168.12.0 255.255.255.0 10.0.0.0 255.0.0.0
Step 12 Configure a transform set that defines how the traffic will be protected:
crypto ipsec transform-set strong esp-3des esp-sha-hmac
Step 13 Define a crypto map:
crypto map toSanJose 20 ipsec-isakmp 
crypto map toSanJose 20 match address 90
crypto map toSanJose 20 set transform-set strong
crypto map toSanJose 20 set peer 209.165.200.229
Step 14 Apply the crypto map to the outside interface:
crypto map toSanJose interface outside
Step 15 Tell the PIX Firewall to implicitly permit IPSec traffic:
sysopt connection permit-ipsec
Example 7-3 lists the configuration for PIX Firewall 1. PIX Firewall default configuration values and certain CA commands are not displayed in configuration listings.

Example 7-3 PIX Firewall 1 with Public CA
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname NewYork
domain-name example.com
fixup protocol ftp 21
fixup protocol http 80
fixup protocol smtp 25
fixup protocol h323 1720
fixup protocol rsh 514
fixup protocol sqlnet 1521
names
pager lines 24
no logging on
interface ethernet0 auto
interface ethernet1 auto
mtu outside 1500
mtu inside 1500
ip address outside 209.165.201.8 255.255.255.224
ip address inside 192.168.12.1 255.255.255.0
no failover
failover ip address outside 0.0.0.0
failover ip address inside 0.0.0.0
arp timeout 14400
nat (inside) 0 0.0.0.0 0.0.0.0 0 0
nat 0 access-list 90
access-list 90 permit ip 192.168.12.0 255.255.255.0 10.0.0.0 255.0.0.0
no rip outside passive
no rip outside default
rip inside passive
no rip inside default
route outside 0.0.0.0 0.0.0.0 209.165.200.227 1
timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00
timeout rpc 0:10:00 h323 0:05:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
sysopt connection permit-ipsec
crypto ipsec transform-set strong esp-3des esp-sha-hmac
crypto map toSanJose 20 ipsec-isakmp
crypto map toSanJose 20 match address 90
crypto map toSanJose 20 set peer 209.165.200.229
crypto map toSanJose 20 set transform-set strong
crypto map toSanJose interface outside
isakmp policy 8 authentication rsa-sig
isakmp policy 8 encryption des
isakmp policy 8 hash sha
isakmp policy 8 group 1
isakmp policy 8 lifetime 86400
ca identity example.com 209.165.202.130:cgi-bin/pkiclient.exe
ca configure example.com ca 1 100 crloptional
telnet timeout 5
terminal width 80
Configuring PIX Firewall 2 with a VeriSign CA

Note The following steps are nearly the same as those in the previous section "Configuring PIX Firewall 1 with a VeriSign CA" for configuring PIX Firewall 2. The differences are in Steps 1 and 2, and Steps 11 to 13, which are specific for the PIX Firewall 2 in this example.

Perform the following steps to configure PIX Firewall 2 for using a VeriSign CA:

Step 1 Define a host name:
hostname SanJose
Step 2 Define the domain name:
domain-name example.com
Step 3 Generate the PIX Firewall RSA key pair:
ca generate rsa key 512
This command is not stored in the configuration.

Step 4 Define VeriSign-related enrollment commands:
ca identity example.com 209.165.202.130
ca configure example.com ca 2 20 crloptional
These commands are stored in the configuration. "2" is the retry period, "20" is the retry count, and the crloptional option disables CRL checking.

Step 5 Authenticate the CA by obtaining its public key and its certificate:
ca authenticate example.com
This command is not stored in the configuration.

Step 6 Request signed certificates from your CA for your PIX Firewall's RSA key pair:
ca enroll example.com abcdef
Before entering this command, contact your CA administrator because they will have to authenticate your PIX Firewall manually before granting its certificate.

"abcdef" is a challenge password. This can be anything. This command is not stored in the configuration.

Step 7 Verify that the enrollment process was successful using the following command:
show ca certificate
Step 8 Save keys and certificates, and the CA commands (except those indicated) in Flash memory:
ca save all
write memory
Note Use the ca save all command any time you add, change, or delete ca commands in the configuration. This command is not stored in the configuration.

Step 9 Create a net static:
static (inside,outside) 10.0.0.0 10.0.0.0
Step 10 Configure an IKE policy:
isakmp enable outside
isakmp policy 8 auth rsa-sig
Step 11 Create a partial access list:
access-list 80 permit ip 10.0.0.0 255.0.0.0 192.168.12.0 255.255.255.0
Step 12 Configure a transform set that defines how the traffic will be protected:
crypto ipsec transform-set strong esp-3des esp-sha-hmac
Step 13 Define a crypto map:
crypto map newyork	 10 ipsec-isakmp 
crypto map newyork 10 match address 80
crypto map newyork 10 set transform-set strong
crypto map newyork 10 set peer 209.165.201.8
Step 14 Apply the crypto map to the outside interface:
crypto map toSanJose interface outside
Step 15 Tell the PIX Firewall to implicitly permit IPSec traffic:
sysopt connection permit-ipsec
Example 7-4 lists the configuration for PIX Firewall 2. PIX Firewall default configuration values and certain CA commands are not displayed in a configuration listing.

Example 7-4 PIX Firewall 2 CA Configuration
nameif ethernet0 outside security0
nameif ethernet1 inside security100
nameif ethernet2 dmz security50
nameif ethernet3 perimeter security40
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname SanJose
domain-name example.com
fixup protocol ftp 21
fixup protocol http 80
fixup protocol smtp 25
fixup protocol h323 1720
fixup protocol rsh 514
fixup protocol sqlnet 1521
names
pager lines 24
no logging on
interface ethernet0 auto
interface ethernet1 auto
interface ethernet2 auto
interface ethernet3 auto
mtu outside 1500
mtu inside 1500
mtu dmz 1500
mtu perimeter 1500
ip address outside 209.165.200.229 255.255.255.224
ip address inside 10.0.0.1 255.0.0.0
ip address dmz 192.168.101.1 255.255.255.0
ip address perimeter 192.168.102.1 255.255.255.0
no failover
failover ip address outside 0.0.0.0
failover ip address inside 0.0.0.0
failover ip address dmz 0.0.0.0
failover ip address perimeter 0.0.0.0
arp timeout 14400
nat (inside) 0 10.0.0.0 255.0.0.0 0 0
nat 0 access-list 80
access-list 80 permit ip 10.0.0.0 255.0.0.0 192.168.12.0 255.255.255.0
no rip outside passive
no rip outside default
no rip inside passive
no rip inside default
no rip dmz passive
no rip dmz default
no rip perimeter passive
no rip perimeter default
route outside 0.0.0.0 0.0.0.0 209.165.200.227 1
timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00
timeout rpc 0:10:00 h323 0:05:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
sysopt connection permit-ipsec
crypto ipsec transform-set strong esp-3des esp-sha-hmac
crypto map newyork 10 ipsec-isakmp
crypto map newyork 10 match address 80
crypto map newyork 10 set peer 209.165.201.8
crypto map newyork 10 set transform-set strong
crypto map newyork interface outside
isakmp policy 8 authentication rsa-sig
isakmp policy 8 encryption des
isakmp policy 8 hash sha
isakmp policy 8 group 1
isakmp policy 8 lifetime 86400
ca identity example.com 209.165.202.130:cgi-bin/pkiclient.exe
ca configure example.com ca 2 20 crloptional
telnet timeout 5
terminal width 80
Using PIX Firewall with an In-House CA

For the general procedures to configure the PIX Firewall for a CA, see "Using Certification Authorities" in Chapter 6, "Configuring IPSec and Certification Authorities." This section provides a specific example for the network illustrated in Figure 7-3 and includes the following topics:

•Scenario Description

•Configuring PIX Firewall 1 for an In-House CA

•Configuring PIX Firewall 2 for an In-House CA

Scenario Description

PIX Firewall supports the use of the following certification authorities (CAs):

•VeriSign support is provided through the VeriSign Private Certificate Services (PCS) and the OnSite service, which lets you establish an in-house CA system for issuing digital certificates.

•Entrust, Entrust VPN Connector, version 4.1 (build 4.1.0.337) or higher. The Entrust CA server is an in-house CA server solution.

•Baltimore Technologies, UniCERT Certificate Management System, version 3.1.2 or higher. The Baltimore CA server is an in-house CA server solution.

•Microsoft Windows 2000, specifically the Windows 2000 Advanced Server, version 5.00.2195 or higher. The Windows 2000 CA server is an in-house CA server solution.

These are all in-house CA servers, except for VeriSign, which provides both a public CA and a private CA solution.

Note The example CA server address is to be used for example purposes only.

The in-house CA server in the following example is placed within the DMZ network of one PIX Firewall network (PIX Firewall 1). The VPN peer, PIX Firewall 2, should enroll and obtain its CA-signed certificates from the CA server residing within the network of PIX Firewall 1. PIX Firewall 2's enrollment and certificate request process is accomplished through the Internet.

The two VPN peers in the configuration examples are shown to be configured to enroll with and obtain their CA-signed certificates from the Entrust CA server. PIX Firewall 1 will obtain its certificate from the CA's local IP address of 10.1.0.2. PIX Firewall 2 will obtain its certificate from the CA's global IP address of 209.165.202.131. After each peer obtains its CA-signed certificate, tunnels can be established between the two VPN peers. The peers dynamically authenticate each other using the digital certificates.

Figure 7-3 VPN Tunnel Network

Configuring PIX Firewall 1 for an In-House CA

Follow these steps to configure PIX Firewall 1 for use with an in-house CA. These steps are similar to the procedure shown in "Using PIX Firewall with a VeriSign CA."

Step 1 Define a host name:
hostname NewYork
Step 2 Define the domain name:
domain-name example.com
Step 3 Generate the PIX Firewall RSA key pair:
ca generate rsa key 512
This command is entered at the command line and does not get stored in the configuration.

Step 4 Define CA-related enrollment commands:
ca identity abcd 209.165.202.131 209.165.202.131
ca configure abcd ra 2 20 crloptional
These commands are stored in the configuration. 2 is the retry period, 20 is the retry count, and the crloptional option disables CRL checking.

Note For a Microsoft CA server, specify the internal network address followed by a colon and the pathname to the server executable, such as 10.1.0.2:/CERTSRV/mscep/mscep.dll.

Step 5 Authenticate the CA by obtaining its public key and its certificate:
ca authenticate abcd
This command is entered at the command line and does not get stored in the configuration.

Step 6 Request signed certificates from your CA for your PIX Firewall's RSA key pair:
ca enroll abcd cisco
Before entering this command, contact your CA administrator because they will have to authenticate your PIX Firewall manually before granting its certificate.

"cisco" is a challenge password. This can be anything. This command is entered at the command line and does not get stored in the configuration.

Step 7 Verify that the enrollment process was successful using the show ca certificate command:
show ca certificate
Step 8 Save keys and certificates, and the CA commands (except those indicated) in Flash memory:
ca save all
write memory
Note Use the ca save all command any time you add, change, or delete ca commands in the configuration. This command is not stored in the configuration.

Step 9 Map a local IP address to a global IP address:
static (dmz, outside) 209.165.202.131 10.1.0.2 netmask 255.255.255.255
Step 10 Permit the host (PIX Firewall 2) to access the global host via LDAP, port 389:
conduit permit tcp host 209.165.202.131 eq 389 209.165.200.229 255.255.255.255
Step 11 Permit the host (PIX Firewall 2) to access the global host via HTTP:
conduit permit tcp host 209.165.202.131 eq http 209.165.200.229 255.255.255.255
Step 12 Configure an IKE policy:
isakmp enable outside
isakmp policy 8 auth rsa-sig
isakmp identity hostname
Step 13 Configure a transform set that defines how the traffic will be protected:
crypto ipsec transform-set strong esp-3des esp-sha-hmac
Step 14 Create a partial access list:
access-list 90 permit ip 192.168.12.0 255.255.255.0 10.0.0.0 255.0.0.0
Step 15 Define a crypto map:
crypto map toSanJose 20 ipsec-isakmp 
crypto map toSanJose 20 match address 90
crypto map toSanJose 20 set transform-set strong
crypto map toSanJose 20 set peer 209.165.200.229
Step 16 Apply the crypto map to the outside interface:
crypto map toSanJose interface outside
Step 17 Tell the PIX Firewall to implicitly permit IPSec traffic:
sysopt connection permit-ipsec
Example 7-5 lists the configuration for PIX Firewall 1.

Example 7-5 PIX Firewall 1 VPN Tunnel Configuration
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname NewYork
domain-name example.com
fixup protocol ftp 21
fixup protocol http 80
fixup protocol smtp 25
fixup protocol h323 1720
fixup protocol rsh 514
fixup protocol sqlnet 1521
names
pager lines 24
no logging on
interface ethernet0 auto
interface ethernet1 auto
mtu outside 1500
mtu inside 1500
ip address outside 209.165.201.8 255.255.255.224
ip address inside 192.168.12.1 255.255.255.0
no failover
failover ip address outside 0.0.0.0
failover ip address inside 0.0.0.0
arp timeout 14400
static (dmz, outside) 209.165.202.131 10.1.0.2 netmask 255.255.255.255
conduit permit tcp host 209.165.202.131 eq 389 209.165.200.229 255.255.255.255
conduit permit tcp host 209.165.202.131 eq http 209.165.200.229 255.255.255.255
nat 0 access-list 90
access-list 90 permit ip 192.168.12.0 255.255.255.0 10.0.0.0 255.0.0.0
no rip outside passive
no rip outside default
rip inside passive
no rip inside default
route outside 10.0.0.0 255.0.0.0 209.165.200.229 1
route outside 0.0.0.0 0.0.0.0 209.165.200.227 1
timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00
timeout rpc 0:10:00 h323 0:05:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
sysopt connection permit-ipsec
crypto ipsec transform-set strong esp-3des esp-sha-hmac
crypto map toSanJose 20 ipsec-isakmp
crypto map toSanJose 20 match address 90
crypto map toSanJose 20 set peer 209.165.200.229
crypto map toSanJose 20 set transform-set strong
crypto map toSanJose interface outside
isakmp policy 8 authentication rsa-sig
isakmp policy 8 encryption des
isakmp policy 8 hash sha
isakmp policy 8 group 1
isakmp policy 8 lifetime 86400
ca identity abcd 209.165.202.131 209.165.202.131
ca configure abcd ra 1 100 crloptional
telnet timeout 5
terminal width 80
Configuring PIX Firewall 2 for an In-House CA

Follow these steps to configure PIX Firewall 2:

Step 1 Define a host name:
hostname SanJose
Step 2 Define the domain name:
domain-name example.com
Step 3 Configure an IKE policy:
isakmp enable outside
isakmp policy 8 auth rsa-sig	
Step 4 Define CA-related enrollment commands:
ca identity abcd 209.165.202.131 209.165.202.131
ca configure abcd ra 2 20 crloptional
These commands are stored in the configuration. 2 is the retry period, 20 is the retry count, and the crloptional option disables CRL checking.

Note For a Microsoft CA server, specify the external (global) network address followed by a colon and the pathname to the server executable, such as 209.165.202.131:/certserv/mscep/mscep.dll.

Step 5 Generate the PIX Firewall RSA key pair:
ca generate rsa key 512
This command is entered at the command line and does not get stored in the configuration.

Step 6 Get the public key and the certificate of the CA server:
ca authenticate abcd
This command is entered at the command line and does not get stored in the configuration.

Step 7 Contact your CA administrator and send your certificate request:
ca enroll abcd cisco
"cisco" is a challenge password. This can be anything. This command is entered at the command line and does not get stored in the configuration.

Step 8 Configure supported IPSec transforms:
crypto ipsec transform-set strong esp-3des esp-sha-hmac
Step 9 Save keys and certificates, and the CA commands (except those indicated) in Flash memory:
ca save all
write memory
Note Use the ca save all command any time you add, change, or delete ca commands in the configuration. This command is not stored in the configuration.

Step 10 Create a partial access list:
access-list 80 permit ip 10.0.0.0 255.0.0.0 192.168.12.0 255.255.255.0
Step 11 Define a crypto map:
crypto map newyork 20 ipsec-isakmp 
crypto map newyork 20 match address 80
crypto map newyork 20 set transform-set strong
crypto map newyork 20 set peer 209.165.201.8
Step 12 Apply the crypto map to the outside interface:
crypto map newyork interface outside
Step 13 Tell the PIX Firewall to implicitly permit IPSec traffic:
sysopt connection permit-ipsec
Example 7-6 lists the configuration for PIX Firewall 2.

Example 7-6 PIX Firewall 2 VPN Tunnel Configuration
nameif ethernet0 outside security0
nameif ethernet1 inside security100
nameif ethernet2 dmz security50
nameif ethernet3 perimeter security40
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname SanJose
domain-name example.com
fixup protocol ftp 21
fixup protocol http 80
fixup protocol smtp 25
fixup protocol h323 1720
fixup protocol rsh 514
fixup protocol sqlnet 1521
names
pager lines 24
no logging on
interface ethernet0 auto
interface ethernet1 auto
interface ethernet2 auto
interface ethernet3 auto
mtu outside 1500
mtu inside 1500
mtu dmz 1500
mtu perimeter 1500
ip address outside 209.165.200.229 255.255.255.224
ip address inside 10.0.0.1 255.0.0.0
ip address dmz 192.168.101.1 255.255.255.0
ip address perimeter 192.168.102.1 255.255.255.0
no failover
failover ip address outside 0.0.0.0
failover ip address inside 0.0.0.0
failover ip address dmz 0.0.0.0
failover ip address perimeter 0.0.0.0
arp timeout 14400
nat 0 access-list 80
access-list 80 permit ip 10.0.0.0 255.0.0.0 192.168.12.0 255.255.255.0
no rip outside passive
no rip outside default
no rip inside passive
no rip inside default
no rip dmz passive
no rip dmz default
no rip perimeter passive
no rip perimeter default
route outside 0.0.0.0 0.0.0.0 209.165.200.227 1
timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00
timeout rpc 0:10:00 h323 0:05:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
sysopt connection permit-ipsec
crypto ipsec transform-set strong esp-3des esp-sha-hmac
crypto map newyork 10 ipsec-isakmp
crypto map newyork 10 match address 80
crypto map newyork 10 set peer 209.165.201.8
crypto map newyork 10 set transform-set strong
crypto map newyork interface outside
isakmp policy 8 authentication rsa-sig
isakmp policy 8 encryption des
isakmp policy 8 hash sha
isakmp policy 8 group 1
isakmp policy 8 lifetime 86400
ca identity abcd 209.165.202.131 209.165.202.131
ca configure abcd ra 1 100 crloptional
telnet timeout 5
terminal width 80
Using an Encrypted Tunnel to Obtain Certificates

This section shows an example of how to perform CA enrollment and certificate requests via a site-to-site VPN tunnel between two PIX Firewall units (PIX Firewall 1 and 2). In the example, both PIX Firewall units enroll and request certificates from a CA server protected by PIX Firewall 1. PIX Firewall 2 enrolls and requests its certificate using an encrypted tunnel.

To accomplish this, you first establish a tunnel between the PIX Firewalls using a pre-shared key. You then use this tunnel to enroll and request the certificate for PIX Firewall 2. After obtaining a certificate, clear the IKE and IPSec SAs on both units and then configure them to use digital certificates.

Note The example CA server address is to be used for example purposes only.

This section includes the following topics:

•Establishing a Tunnel Using a Pre-Shared Key

•Establishing a Tunnel with a Certificate

This example uses the network diagram shown in Figure 7-4.

Figure 7-4 VPN Tunnel Network

Establishing a Tunnel Using a Pre-Shared Key

This section describes how to establish a tunnel using a pre-shared key. It includes the following topics:

•PIX Firewall 1 Configuration

•PIX Firewall 2 Configuration

PIX Firewall 1 Configuration

Follow these steps to configure PIX Firewall 1:

Step 1 Define a host name:
hostname NewYork
Step 2 Define the domain name:
domain-name example.com
Step 3 Configure an IKE policy:
isakmp enable outside
isakmp policy 8 auth pre-share
isakmp key cisco address 209.165.200.229 netmask 255.255.255.255
Step 4 Create a partial access list:
access-list 90 permit ip host 10.1.0.2 host 209.165.200.229
Step 5 Configure NAT 0:
nat (dmz) 0 access-list 90
Step 6 Configure a transform set that defines how the traffic will be protected:
crypto ipsec transform-set strong esp-3des esp-sha-hmac
Step 7 Define a crypto map:
crypto map toSanJose 20 ipsec-isakmp 
crypto map toSanJose 20 match address 90
crypto map toSanJose 20 set transform-set strong
<