Configuring the PIX Firewall and VPN Clients Using PPTP, MPPE and IPSec

Introduction

In this sample configuration, four different kinds of clients connect and encrypt traffic with the Cisco Secure PIX Firewall as tunnel endpoint:

• Users that run Cisco Secure VPN Client 1.1 on Microsoft Windows 95/98/NT

• Users that run the Cisco Secure VPN 3000 Client 2.5.x on Windows 95/98/NT

• Users that run native Windows 98/2000/XP Point-to-Point Tunneling Protocol (PPTP) clients

• Users that run the Cisco VPN Client 3.x/4.x on Windows 95/98/NT/2000/XP

In this example, a single pool for IPsec and PPTP is configured. However, the pools can also be made separate.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on these software and hardware versions:

• PIX Software Release 6.3.3

• Cisco Secure VPN Client 1.1

• Cisco VPN 3000 Client version 2.5

• Cisco VPN Client 3.x and 4.x

• Microsoft Windows 2000 and Windows 98 clients

Note: This was tested on PIX Software Release 6.3.3 but should work on release 5.2.x and 5.3.1. PIX Software Release 6.x is required for the Cisco VPN Client 3.x and 4.x. (Support for the Cisco VPN 3000 Client 2.5 is added in PIX Software Release 5.2.x. The configuration also works for PIX Software Release 5.1.x, except for the Cisco VPN 3000 Client part.) IPsec and PPTP/Microsoft Point-to-Point Encryption (MPPE) should be made to work separately first. If they do not work separately, they do not work together.

Note: PIX 7.0 uses the inspect rpc command to handle RPC packets. The inspect sunrpc command enables or disables application inspection for the Sun RPC protocol. Sun RPC services can run on any port on the system. When a client attempts to access an RPC service on a server, it must find out which port that particular service runs on. It does this by querying the portmapper process on the well-known port number 111. The client sends the RPC program number of the service, and gets back the port number. From this point on, the client program sends its RPC queries to that new port.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

Refer to the Cisco Technical Tips Conventions for more information on document conventions.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool (registered customers only) to obtain more information on the commands used in this section.

Network Diagram

This document uses the network setup shown in this diagram.

Configurations

This document uses these configurations.

• Cisco Secure PIX Firewall

• Cisco Secure VPN Client 1.1

PIX Version 6.3(3)
interface ethernet0 auto
interface ethernet1 100full
nameif ethernet0 outside security0
nameif ethernet1 inside security100
enable password 8Ry2YjIyt7RRXU24 encrypted
passwd 2KFQnbNIdI.2KYOU encrypted
hostname goss-515A
fixup protocol ftp 21
fixup protocol h323 h225 1720
fixup protocol h323 ras 1718-1719
fixup protocol http 80
fixup protocol ils 389
fixup protocol rsh 514
fixup protocol rtsp 554
fixup protocol sip 5060
fixup protocol sip udp 5060
fixup protocol skinny 2000
fixup protocol smtp 25
fixup protocol sqlnet 1521
names
access-list 101 permit ip 10.99.99.0 255.255.255.0 192.168.1.0 255.255.255.0
pager lines 24
mtu outside 1500
mtu inside 1500
ip address outside 172.18.124.152 255.255.255.0
ip address inside 10.99.99.1 255.255.255.0
ip audit info action alarm
ip audit attack action alarm
ip local pool bigpool 192.168.1.1-192.168.1.254
pdm history enable
arp timeout 14400
nat (inside) 0 access-list 101
timeout xlate 3:00:00
timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h225 1:00:00
timeout h323 0:05:00 mgcp 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius
aaa-server LOCAL protocol local
no snmp-server location
no snmp-server contact
snmp-server community public
no snmp-server enable traps
floodguard enable
sysopt connection permit-ipsec
sysopt connection permit-pptp
crypto ipsec transform-set myset esp-des esp-md5-hmac
crypto dynamic-map dynmap 10 set transform-set myset
crypto map mymap 10 ipsec-isakmp dynamic dynmap
crypto map mymap client configuration address initiate
crypto map mymap client configuration address respond
crypto map mymap interface outside
isakmp enable outside

!--- Cisco Secure_VPNClient_key.


isakmp key ******** address 0.0.0.0 netmask 0.0.0.0
isakmp identity address
isakmp client configuration address-pool local bigpool outside


!--- ISAKMP Policy for Cisco VPN Client 2.5 or !--- Cisco Secure VPN Client 1.1.


isakmp policy 10 authentication pre-share
isakmp policy 10 encryption des
isakmp policy 10 hash md5


!--- The 1.1 and 2.5 VPN Clients use Diffie-Hellman (D-H) !--- group 1 policy (PIX default).


isakmp policy 10 group 1
isakmp policy 10 lifetime 86400


!--- ISAKMP Policy for VPN Client 3.0 and 4.0.


isakmp policy 20 authentication pre-share
isakmp policy 20 encryption des
isakmp policy 20 hash md5


!--- The 3.0/4.0 VPN Clients use D-H group 2 policy !--- and PIX 6.0 code.


isakmp policy 20 group 2
isakmp policy 20 lifetime 86400
vpngroup vpn3000-all address-pool bigpool
vpngroup vpn3000-all dns-server 10.99.99.99
vpngroup vpn3000-all wins-server 10.99.99.99
vpngroup vpn3000-all default-domain password
vpngroup vpn3000-all idle-time 1800


!--- VPN 3000 group_name and group_password.


vpngroup vpn3000-all password ********
telnet timeout 5
ssh timeout 5
console timeout 0
vpdn group 1 accept dialin pptp
vpdn group 1 ppp authentication pap
vpdn group 1 ppp authentication chap
vpdn group 1 ppp authentication mschap
vpdn group 1 ppp encryption mppe auto
vpdn group 1 client configuration address local bigpool
vpdn group 1 pptp echo 60
vpdn group 1 client authentication local


!--- PPTP username and password.


vpdn username cisco password *********
vpdn enable outside
terminal width 80
Cryptochecksum:d41d8cd98f00b204e9800998ecf8427e
: end
goss-515A#

1- TACconn 
      My Identity
           Connection security: Secure
           Remote Party Identity and addressing
           ID Type: IP subnet
           10.99.99.0
            255.255.255.0
           Port all Protocol all

      Connect using secure tunnel
           ID Type: IP address
           172.18.124.152
 
      Pre-shared Key=CiscoSecure_VPNClient_key

      Authentication (Phase 1) 
      Proposal 1 
          Authentication method: pre-shared key
          Encryp Alg: DES 
          Hash Alg: MD5 
          SA life: Unspecified
          Key Group: DH 1
 
      Key exchange (Phase 2) 
      Proposal 1 
          Encapsulation ESP 
          Encrypt Alg: DES 
          Hash Alg: MD5 
          Encap: tunnel 
          SA life: Unspecified
          no AH 
 
  2- Other Connections 
         Connection security: Non-secure 
         Local Network Interface
           Name: Any 
           IP Addr: Any 
           Port: All

Cisco VPN 3000 Client 2.5.x or Cisco VPN Client 3.x and 4.x

Select Options > Properties > Authentication. Group-name and group password match the group_name and group_password on the PIX as in:

vpngroup vpn3000-all password ******** 
Host-name = 172.18.124.152 

Windows 98/2000/XP PPTP Client Setup

You can contact the vendor who makes the PPTP client. Refer to How to Configure the Cisco Secure PIX Firewall to Use PPTP for information on how to set this up.

Verify

There is currently no verification procedure available for this configuration.

Troubleshoot

This section provides information you can use to troubleshoot your configuration.

Troubleshooting Commands

The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT to view an analysis of show command output.

Note: Refer to Important Information on Debug Commands before you use debug commands.

PIX IPsec Debug

• debug crypto ipsec—Displays the IPsec negotiations of phase 2.

• debug crypto isakmp—Displays the Internet Security Association and Key Management Protocol (ISAKMP) negotiations of phase 1.

• debug crypto engine—Displays the traffic that is encrypted.

PIX PPTP Debug

• debug ppp io—Displays the packet information for the PPTP PPP virtual interface.

• debug ppp error—Displays PPTP PPP virtual interface error messages.

• debug vpdn error—Displays PPTP protocol error messages.

• debug vpdn packets—Displays PPTP packet information about PPTP traffic.

• debug vpdn events—Displays PPTP tunnel event change information.

• debug ppp uauth—Displays the PPTP PPP virtual interface AAA user authentication debugging messages.

Microsoft Related Issues

• How to Keep RAS Connections Active After Logging Off —When you log off from a Windows Remote Access Service (RAS) client, any RAS connections are automatically disconnected. In order to remain connected after you log off, enable the KeepRasConnections key in the registry on the RAS client.

• User Is Not Alerted When Logging On with Cached Credentials —Symptoms - When you attempt to log on to a domain from a Windows-based workstation or member server and a domain controller cannot be located, no error message is displayed. Instead, you are logged on to the local computer using cached credentials.

• How to Write an LMHOSTS File for Domain Validation and Other Name Resolution Issues —There can be instances when you experience name resolution issues on your TCP/IP network and you need to use Lmhosts files to resolve NetBIOS names. This article discusses the proper method of creating an Lmhosts file to aid in name resolution and domain validation.

Related Information

• IPsec Negotiation/IKE Protocols Support Pages
• PIX Command Reference
• Cisco PIX 500 Series Security Appliances Support Page
• Requests for Comments (RFCs)
• Configuring IPsec Network Security
• Configuring Internet Key Exchange Security Protocol
• Technical Support & Documentation- Cisco Systems