Maintenance Limitations of the PIX Firewall

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9.3 Configuring the PIX as a Gateway

The PIX firewall comes standard with two switchable 10100 Megabit Ethernet cards, a serial console port, a failover control card, some required cabling and mounting parts, and possibly a secure encryption card, depending on the bundle purchased. In this section we will set up a PIX unit right out of the box, configure it for basic operation, and set up an average firewall. Beyond that, we will illustrate the setup of multiple PIX units so that they may link to one another across the Internet, thus creating a VPN. In this section, we show you how to connect to the PIX so you can configure it, how to set up your firewall on the PIX, and how to do some initial testing. Configuration of the PIX doesnt affect configuration of any other hosts on the inner or outer networks, which you can still set up using traditional rules. The configuration examples in this chapter were set up using the 4.1.6 version of the PIX operating software.

9.3.1 Connecting to the PIX

Example 9-1 shows the PIX boot screen, which is sent to the console port when the unit powers on. A serial console cable, supplied with the unit, must be attached to a personal computer, and the terminal software must be configured as follows before any commands may be input into the system: • 9600 baud • 8 bits, no parity, 1 stop bit To confirm that the connections are made properly and that the terminal software is set up right, simply booting the PIX firewall should produce the output seen in Example 9-1 . Example 9-1. PIX Console Startup Screen Copyright c 1996-1998 by Cisco Systems, Inc. Restricted Rights Legend Use, duplication, or disclosure by the Government is subject to restrictions as set forth in subparagraph c of the Commercial Computer Software - Restricted Rights clause at FAR sec. 52.227-19 and subparagraph c 1 ii of the Rights in Technical Data and Computer Software clause at DFARS sec. 252.227-7013. Cisco Systems, Inc. 170 West Tasman Drive San Jose, California 95134-1706 Type ? for help armadillo 0

9.3.2 A Sample Configuration

The configuration of the firewall is pretty straightforward. Given our test scenario featured in Figure 9-2 , we have developed a configuration that meets those requirements. Here are the configuration parameters we entered into our PIX: 151 nameif ethernet0 outside security0 nameif ethernet1 inside security100 enable password testing password testing hostname lab-test-1 no failover names pager lines 24 syslog output 20.3 no syslog console syslog host 192.168.2.2 interface ethernet0 auto interface ethernet1 auto ip address outside 1.251.174.156 255.255.255.248 ip address inside 192.168.2.1 25.255.255.0 arp timeout 14400 global outside 1 2.241.11.249-2.241.11.251 global outside 2 2.241.11.252-2.241.11.254 nat inside 2 192.168.2.128 255.255.255.128 age 10 route outside 0.0.0.0 0.0.0.0 1.251.174.154 1 no rip outside passive no rip outside default no rip inside passive no rip inside default timeout xlate 24:00:00 conn 12:00:00 udp 00:02:00 timeout rpc 00:10:00 h323 00:05:00 uauth 00:05:00 no snmp-server location no snmp-server contact snmp-server community public telnet 192.168.2.2 255.255.255.255 mtu outside 1500 mtu insde 1500 The two nameif commands assign short names to the two interfaces: outside and inside . Then, the two interface commands define the speed at which the interfaces operate. We used the auto keyword to have the hardware automatically sync to the Ethernet it is attached to. The ip address commands use the assigned names to establish the network configuration for the internal and external networks. The internal network we chose was part of the unroutable RFC 1918 network 192.168.0.0, which is traditionally used for hosts requiring Network Address Translation NAT on an interior network protected by a firewall such as the PIX. As Figure 9-1 depicts, we dont have an internal router. The network that we used for testing was very small and an internal router was not necessary. You can see this in the configuration by studying the route command entry, which points the default route 0.0.0.0 to the gateway to which the PIX would send external traffic 1.251.174.154. Logically enough, you are always required to specify an outside router. The rip command sets whether the PIX should or should not broadcast default routing information using the RIP protocol to either the inside or outside interface. Our sample configuration disables all RIP route propagation since we had such a small example. Should you have an internal router that extends the network to other locations, you would need to set the default internal route mentioned above to the router responsible for accessing the rest of