Superior to Unix and other router firewalls
9.2.2.3 Single point of controlfailure
When network trouble is at hand, a clear delineation between the outside world and ones local world is an immense asset. By using a single unit to handle the networks entire firewalling needs, the network coordinator has a clear starting point for troubleshooting. The PIX provides such an architecture. By having a single unit handle all network traffic in this manner, equipment malfunction and software misconfiguration could cause a great amount of havoc in one fell swoop. But Cisco has anticipated this problem with a fail-over, hot-standby mode, whereby two units can be configured in parallel. Should some fault occur to one of the units, the other can support the firewall by maintaining operation transparently.9.2.2.4 Dynamic address translation
The dynamic translation feature, which allows users to pick up a free address from the Internet pool whenever they need one, does more than just allow many people to share a few NIC registered addresses. It also provides adaptive security to the hosts using the internal addresses. The PIX unit has two interfaces, one for the exterior network and one for the interior one. Because of this, the internal address range is hidden by translating the internal address into the dynamic pool of addresses for Internet exchange. This method provides a high level of security because a threat is much less likely when an attacker doesnt know the architecture, network range, or setup of the internal network9.2.2.5 PIX acts like a proxy server
Unix-based proxy servers are commonplace in todays world, and most of them serve their function well. Proxy servers do essentially what the PIX firewall was engineered to do: they hide a machine or a network of machines from the outside world by masquerading as the client in network conversations with unknown or unverifiable parties. The PIX is more robust than the standard proxy servers because it provides a quick session bypass once the authenticated parties have shaken hands. Traditional proxy servers maintain state information for the duration of the session, and handle their packet control at the top of the protocol stack. Moreover, because software-driven proxy servers perform packet filtering, they prevent the use of almost all the VPN solutions on the market today.9.2.2.6 Ease of configuration and maintenance
For the most part, the PIX is very easy to handle in everyday use. Once the configuration is applied and tested, it handles its job silently and without complaint. As is popular in todays world, to further assist the network coordinators that will be installing the device, Cisco has made an HTML front end for configuration. There is of course the old standby option of the command-line-driven interface, which could be used by those more familiar with Ciscos prevalent IOS software. 1499.2.2.7 High-speed access
For those with ultra-high-capacity lines, such as fractional or full DS3s T3s, the PIX, with its two 100-megabit Ethernet cards, can easily handle a significant amount of Internet traffic. Although we wouldnt recommend piping a T3s full load of traffic through only one machine, the fact that the capacity is there is quite a benefit.9.2.2.8 Links
By using an additional card that comes separately, the PIX firewall can be used to create an encrypted channel between itself and another such unit somewhere out on the public side of the PIX. This private link encryption feature gives the PIX firewall its most tremendous benefit: it lets organizations link private Internets securely using the public networks, with very simple configuration. Thats what this book is all about. One slight disadvantage is that the PIX firewall supports only IP traffic. We suppose this could be considered an advantage as well.9.2.3 Limitations of the PIX Firewall
Even though the PIX is a nearly complete solution to the development of a virtually private network, it does have some drawbacks in terms of maintenance, network address translation limits, and price.9.2.3.1 Hardware solution
Hardware can be tricky if mismanaged, difficult to debug if misconfigured, and hard to replace quickly if broken. Hardware like the PIX is provided by only one vendor, and you cant be sure what will happen to the vendor in the future.9.2.3.2 Dynamic address use
There is a limited pool of addresses that the PIX can assign to hosts on your internal network that want to communicate with the outside. Cisco sells a few different varieties of the product, allowing for 32, 256, or 1024 sessions simultaneously. Remember that one user could be using many different sessions at once, so there is a definite limit on how much a PIX can handle when its connected to a huge network.9.2.3.3 Budgetary considerations
A whole squadron of Cisco PIX units might be prohibitively expensive to widely distribute across your network. The PIX firewall has a suggested retail price in the tens of thousands of dollars, and the encryption cards required to create VPN tunnels go for a few thousand each.9.2.3.4 Maintenance
As with any new equipment, you have to consider the need for ongoing maintenance and growth. The PIX firewall, which may be initially easy to configure, could grow to have a complex configuration even if there are no other firewalls providing a similar function. The persons in charge of coordinating network activity need to establish a plan for how traffic needs to be restricted, and to which networks these restrictions apply. Subtle mistakes in the configuration could lead to potentially large security holes.Parts
» Virtual Private Networks 2nd 1999
» How VPNs relate to Intranets
» What Are We Protecting with Our VPN?
» Firewalls How VPNs Solve Internet Security Issues
» Authentication How VPNs Solve Internet Security Issues
» Encryption How VPNs Solve Internet Security Issues
» Tunneling How VPNs Solve Internet Security Issues
» A Note on IP Address and Domain Name Conventions Used in This Book
» Packet restriction or packet filtering routers
» Bastion host What Types of Firewalls Are There?
» DMZ or perimeter zone network
» Proxy servers What Types of Firewalls Are There?
» A Brief History of Cryptography
» Cryptography: How to Keep a Secret
» Cryptography in Network Communications
» Hash algorithms Cryptographic Algorithms
» Secret key systems Cryptographic Algorithms
» Public key cryptosystems Cryptographic Algorithms
» Use of Cryptosystems and Authentication in a VPN
» ESP Encapsulating Security Payload
» AH Authentication Header VPN Protocols
» Internet Key Exchange, ISAMKPOakley
» ISO X.509 v.3 Digital Certificates
» LDAP Lightweight Directory Access Protocol Radius
» PPTP Point-to-Point Tunneling Protocol
» Basic Firewalling Methodologies for Compromising VPNs
» Ciphertext-only attack Cryptographic Assaults
» Known plaintext attack Cryptographic Assaults
» Chosen plaintext attack Cryptographic Assaults
» Chosen ciphertext attack Cryptographic Assaults
» Brute force attacks Cryptographic Assaults
» Password guessers and dictionary attacks
» Social engineering Cryptographic Assaults
» Address spoofing Network Compromises and Attacks
» Session hijacking Network Compromises and Attacks
» Man-in-the-middle attack Network Compromises and Attacks
» Replay attack Network Compromises and Attacks
» Detection and cleanup Network Compromises and Attacks
» Patents and Legal Ramifications
» General WAN, RAS, and VPN Concepts
» Telco Small to Medium Solutions
» Security, scalability, and stability
» Hardwaresoftware Small to Medium Solutions
» Administration Small to Medium Solutions
» Hardwaresoftware Administration Security, scalability, and stability
» Differences Between PPTP, L2F, and L2TP
» Dialing into an ISP That Supports PPTP
» Dialing into an ISP That Doesnt Support PPTP
» Where PPTP Fits into Our Scenario
» The encapsulation process Dissecting a PPTP Packet
» Accept encrypted authentication RAS authentication methods
» Accept Microsoft encrypted authentication
» Accept any authentication, including clear text
» Data encryption PPTP Security
» Availability Features of PPTP
» Easy Implementation Features of PPTP
» Multiprotocol Tunneling Features of PPTP
» Ability to Use Corporate and UnregisteredIP Addresses
» Choosing the protocols to tunnel
» Choosing your authentication method
» IP address negotiation using DHCP
» Outbound authentication using PPTP filtering
» Filtering caveats PPTP Filtering
» Installing PPTP Filtering by IP Address
» Configuring Users for Dial-up Access
» Configuring PPTP for Dial-up Networking on a Windows NT Client
» Configuring PPTP for Dial-up Networking on a Windows 95 or 98 Client
» Setting up global PPTP parameters Setting up a port for PPTP
» Configuring PPTP on an Ascend MAX 4004
» Making the Calls Configuring and Testing Layer 2 Connections
» The Event Viewer Login problems
» The Dial-Up Networking Monitor
» ping and traceroute Connectivity Testing
» Fixed IP addresses How to Allow PPTP Through Firewalls
» How PPTP Can Bypass a Proxy Server
» Three-part encryption technique Security
» Support for an emerging security standard
» Support for Security Dynamics SecureID
» Accessibility Flexibility Advantages of the AltaVista Tunnel System
» Platform Limitations AltaVista Tunnel Limitations
» Extranet server System Considerations
» Telecommuter client System Considerations
» Planning How the AltaVista Tunnel Works
» AltaVista Tunnel Extranet server
» Security procedures The Guts
» AltaVista Tunnel Telecommuter Client
» Sample configuration Implementing a LAN-to-LAN Tunnel
» Tunnel server configuration Implementing a LAN-to-LAN Tunnel
» Firewall configuration Host configuration
» Sample configuration Implementing Single Connections-to-LAN Tunnels
» Tunnel server configuration Implementing Single Connections-to-LAN Tunnels
» Firewall configuration Implementing Single Connections-to-LAN Tunnels
» Local host configuration Implementing Single Connections-to-LAN Tunnels
» Remote PC configuration Implementing Single Connections-to-LAN Tunnels
» Sample configuration Implementing PC-to-WAN Tunnels
» Tunnel server configuration Implementing PC-to-WAN Tunnels
» Tracing the packets Implementing PC-to-WAN Tunnels
» Preparing to Install Installing the AltaVista Tunnel
» Windows NT 4.0 Installing the AltaVista Tunnel Extranet Serverfor Windows NT
» Installing the AltaVista Tunnel Telecommuter Client for Windows
» Installing the AltaVista Tunnel Telecommuter Client for MacOS
» Initial configuration Adding Routes and Dynamic Addresses
» Managing routes and dynamic IPs
» Group configuration Adding Tunnel Groups
» Tunnel client information Adding Tunnel Groups
» Tools for Tunnel Management Changing Port Settings
» Rekey Interval and Minimum Encryption Settings
» Configuring Unix-to-Windows NT Tunnel Connections
» Getting Busy Configuring the AltaVista Telecommuter Client
» Tunnel Server and Client Configuration Checks
» Local Network and Internet Gateway Configuration Checks
» Encryption Capabilities The SSH Software
» Useful sshd parameters for our purposes
» Understanding SSH authentication ssh
» Useful ssh parameters for our purposes
» The VPN Components Creating a VPN with PPP and SSH
» Setting up the master and slave Linux systems
» Creating a user account on the slave
» Setting up SSH authentication
» Configuring sudo on the slave
» Putting pty-redir on the master
» Setting up the slaves scripts
» Testing the Connection Creating a VPN with PPP and SSH
» A Performance Evaluation Creating a VPN with the Unix Secure Shell
» ISP Assigned Addresses Global Pool
» Hardware solution Advantages of the PIX Firewall
» Superior to Unix and other router firewalls
» Single point of controlfailure
» Dynamic address translation Advantages of the PIX Firewall
» PIX acts like a proxy server
» Ease of configuration and maintenance
» High-speed access Advantages of the PIX Firewall
» Links Advantages of the PIX Firewall
» Hardware solution Limitations of the PIX Firewall
» Dynamic address use Limitations of the PIX Firewall
» Budgetary considerations Limitations of the PIX Firewall
» Maintenance Limitations of the PIX Firewall
» A Sample Configuration Configuring the PIX as a Gateway
» Firewall Configuration on the PIX
» debug xlate Testing, Tracing, and Debugging
» arp Testing, Tracing, and Debugging
» show interface Testing, Tracing, and Debugging
» Offering Services to the Internet Through Conduits and the static Command
» Tunneling with the link Directive
» Choosing an ISP Managing and Maintaining Your VPN
» Connectivity Problems Solving VPN Problems
» Authentication Errors Solving VPN Problems
» Routing Problems Dealing with an ISP
» Compatibility with Other Products
» Delivering Quality of Service
» Restrict What VPN Users Can Get To
» Avoid Public DNS Information for VPN Servers and Routers
» Keeping Yourself Up-to-Date Managing and Maintaining Your VPN
» Network Connections Hardware and Operating System VPN Package
» Connection Hardware and Operating System VPN Package
» Connection Hardware and Operating System
» VPN Package Remote Access Users
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