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Before using this chapter, be sure that you have planned your site's security policy, as described in Chapter 1, "Introduction," and configured the PIX Firewall, as described in Chapter 2, "Configuring the PIX Firewall."
This chapter provides network diagrams and the configuration instructions to create them. Further information about the commands in the configurations can be found in Chapter 5, "Command Reference."
If you are starting a configuration, you may want to use the forms provided in Appendix A, "Configuration Forms" to help you plan a configuration.
Acronyms in the text are defined in Appendix B, "Acronyms and Abbreviations."
The following topics are discussed:
When you first add a PIX Firewall to an existing network, it is easiest to implement its use if you do not have to renumber all the inside and outside IP addresses. The configuration in Figure 4-1 illustrates this scenario. Syslog is enabled to facilitate troubleshooting. All inside hosts can start connections. All external hosts are blocked from initiating connections or sessions on inside hosts. If you use Inter-NIC registered IP addresses, only use those addresses that you own.
Table 4-1 lists the configuration.
| Configuration | Description |
|---|---|
nameif ethernet0 outside security0 nameif ethernet1 inside security100 interface ethernet0 auto interface ethernet1 auto | PIX Firewall provides nameif command statements for the inside and outside interfaces and the interface command statements for both interfaces in the default configuration (default configuration command statements are shown in boldface italic screen font). |
ip address outside 192.150.50.3 255.255.255.0 ip address inside 172.31.2.100 255.0.0.0 | Identify the IP addresses for both interfaces. |
hostname pixfirewall | Specifies the host name for the PIX Firewall. This name appears in the command line prompt. |
arp timeout 14400 | Sets the ARP timeout to 14,400 seconds (four hours). Entries are kept in the ARP table for four hours before they are flushed. Four hours is the standard default value for ARP timeouts. |
no failover | Disables failover access. |
names | Enables use of text strings instead of IP addresses. This makes your configuration files more readable. |
pager lines 24 | Enables paging so that if when 24 lines of information display, PIX Firewall pauses the listing and prompts you to continue. |
logging buffered debugging | Enables syslog messages, which provide diagnostic information and status for the PIX Firewall. PIX Firewall makes it easy to view syslog messages with the show logging command. |
nat (inside) 0 172.31.2.0 255.0.0.0 | Lets inside IP addresses be recognized on the outside network and lets inside users start outbound connections. |
rip inside default no rip inside passive no rip outside default rip outside passive | Sets RIP listening attributes. The first command causes the PIXFirewall to broadcast a default route on the inside interface. Broadcasting a default route sends network traffic to the PIX Firewall if your internal network is running RIP. The next command disables passive RIP listening on the inside. The next command disables broadcasting a default route on the outside. This is desirable when the network is attached to the Internet, but not when on an intranet. The last command enables passive RIP listening on the outside. |
route outside 0.0.0.0 0.0.0.0 192.150.50.1 1 | Sets the outside default route to the router attached to the Internet. |
timeout xlate 3:00:00 conn 1:00:00 half-closed0:10:00 udp 0:02:00 timeout rpc 0:10:00 h323 0:05:00 timeout uauth 0:05:00 absolute | Default values for the maximum duration that PIX Firewall resources can remain idle until being freed. Additional users cannot make connections until a connection resource is freed either by a user dropping a connection or by an xlate and conn timer time out. |
no snmp-server location no snmp-server contact snmp-server community public | Specifies that SNMP information may be accessed by internal hosts that know the community string, but PIX Firewall does not send trap information to any host. |
mtu outside 1500 mtu inside 1500 | Sets the maximum transmission unit value for Ethernet access. |
In Figure 4-2, the PIX Firewall has two interfaces. In this configuration, there is no user authentication, no authorization, and no syslog or SNMP logging of troubleshooting messages. All inside users can start outbound connections and all connections from the outside are dropped. A configuration such as this is a good example of the basic commands used to create a secured network.
-Interface Configuration
Table 4-2 lists the configuration.
| Configuration | Description |
|---|---|
nameif ethernet0 outside security0 nameif ethernet1 inside security100 interface ethernet0 auto interface ethernet1 auto | PIX Firewall provides nameif command statements for the inside and outside interfaces and the interface command statements for both interfaces in the default configuration (default configuration command statements are shown in boldface italic screen font). |
ip address outside 192.150.50.3 255.255.255.0 ip address inside 10.0.0.3 255.0.0.0 | Identify the IP addresses for both interfaces. |
arp timeout 14400 | Set the ARP timeout to 14,400 seconds (four hours). Entries are kept in the ARP table for four hours before they are flushed. |
nat (inside) 1 0 0 | Permit all inside users to start outbound connections using the translated IP addresses from the global pool. |
global (outside) 1 192.150.50.76-192.150.50.85 global (outside) 1 192.150.50.75 | Create a pool of global addresses that translated addresses use when they exit the firewall from the protected networks to the unprotected networks. The global command statement is associated with a nat command statement by the nat_ID, which in this example is 1. Because there are only 9 IP addresses in the pool, a PAT (Port Address Translation) global is added to handle overflow. |
no rip inside default no rip inside passive no rip outside default no rip outside passive | PIX Firewall does use RIP information for its forwarding decisions, but these commands can be useful for broadcasting a default route---if your network uses the RIP protocol. However, most do not. In most cases, you can ignore these command statements. |
route outside 0.0.0.0 0.0.0.0 192.150.50.1 1 | Set the outside default route to the router attached to the Internet. |
timeout xlate 3:00:00 conn 1:00:00 half-closed0:10:00 udp 0:02:00 timeout rpc 0:10:00 h323 0:05:00 timeout uauth 0:05:00 absolute | Default values for the maximum duration that PIX Firewall resources can remain idle until being freed. Additional users cannot make connections until a connection resource is freed either by a user dropping a connection or by an xlate and conn timer time out. |
conduit permit icmp any any | Allows inbound and outbound pings. |
no snmp-server location no snmp-server contact snmp-server community public | Specifies that SNMP information may be accessed by internal hosts that know the community string, but PIX Firewall does not send trap information to any host. |
telnet 10.0.0.100 255.255.255.255 telnet timeout 15 | Specifies that host 10.0.0.100 is permitted to access the PIX Firewall console via Telnet and that 15 minutes are allowed before the idle timer runs out and the session is logged off. |
mtu outside 1500 mtu inside 1500 | Sets the maximum transmission unit value for Ethernet access. |
The configuration in Figure 4-3 provides an overview of how the various commands are used to create a configuration.
This configuration shows the use of PAT (Port Address Translation), denying Java applets, using the AAA commands, creating a mail server, permitting NFS, initializing SNMP, and setting console access with Telnet.
Table 4-3 lists the configuration.
| Configuration | Description |
|---|---|
nameif ethernet0 outside security0 nameif ethernet1 inside security100 interface ethernet0 auto interface ethernet1 auto | PIX Firewall provides nameif command statements for the inside and outside interfaces and the interface command statements for both interfaces in the default configuration (default configuration command statements are shown in boldface italic screen font). |
ip address inside 10.1.1.1 255.0.0.0 ip address outside 204.31.17.10 255.255.255.0 | Identify the IP addresses for both interfaces. |
logging on logging host 10.1.1.11 logging trap 7 logging facility 20 no logging console | The logging host command statement specifies which host runs a syslog server. This command also causes the PIXFirewall to start sending syslog messages to that host. The logging trap command statement sets syslog to send all possible messages to the syslog host. The no logging console command statement disables displaying messages to the console. |
arp timeout 600 | Set an ARP timeout to 600 seconds (10 minutes). Use this arp timeout command statement when you set up a network and change inside and outside host addresses often. |
nat (inside) 1 10.0.0.0 255.0.0.0 nat (inside) 2 192.168.3.0 255.255.255.0 | Permit all inside users to start outbound connections using the translated IP addresses from the global pool. |
global (outside) 1 204.31.17.25-204.31.17.27 global (outside) 1 204.31.17.24 global (outside) 2 192.159.1.1-192.159.1.254 | Create two pools of global addresses to let the nat command statements use the address pools for translating internal IP addresses to external addresses. Each pool is designated by the number from the nat command statement, in this case, 1 and 2. Pool 1 consists of four IP addresses, the first three in the G7 from 204.31.17.25 to 204.31.17.27, and a PAT address, 204.31.17.28. The PAT address lets up to 64,000 hosts be translated through this single address. Pool 2 consists of 254 hosts from 192.159.1.1 to 192.159.1.254. |
conduit permit icmp any any | Allow inbound and outbound pings. |
outbound 10 deny 192.168.3.3 255.255.255.255 1720 outbound 10 deny 0 0 80 outbound 10 permit 192.168.3.3 255.255.255.255 80 outbound 10 deny 192.168.3.3 255.255.255.255 java outbound 10 permit 10.1.1.11 255.255.255.255 80 | Create access lists to determine which hosts can access services. The first outbound command statement denies host 192.168.3.3from accessing H.323 (port 1720) services such as MS NetMeeting or InternetPhone. The next command statement denies all hosts from accessing the Web (port 80). The next two command statements permits host 192.168.3.3 to use the Web, but denies its users from downloading Java applets. The last outbound command statement permits host 10.1.1.11 access to the Web (at port 80) and to download Java applets. This permit command statement outweighs the previous deny regardless of the order in which the command statements are entered into the configuration. |
apply (inside) 10 outgoing_src | Specify that the outbound group regulates the activities of inside hosts starting outbound connections. |
no rip outside passive no rip outside default rip inside passive rip inside default | The first command disables RIP listening on the outside interface. The second command disables broadcasting a default route on the outside. The third command enables RIP listening on the inside and the last command causes PIX Firewall to broadcast a default route on the inside interface. |
route outside 0 0 204.31.17.1 1 | Set the default route on the outside network to be 204.31.17.1. This is the IP address of the host connecting to the Internet. |
tacacs-server host 10.1.1.12 1q2w3e aaa authentication any inside 192.168.3.0 255.255.255.0 0 0 tacacs+ aaa authorization any inside 192.168.3.0 255.255.255.0 0 0 | The tacacs-server command specifies the IP address of the TACACS+ authentication server. The aaa authentication command statement specifies that users on network 192.168.3.0 starting FTP, HTTP, and Web connections from the inside interface be prompted for their usernames and passwords before being permitted to access these servers on other interfaces. The aaa authorization command statement lets the users on 192.168.3.0 access FTP, HTTP, or Telnet, and any TCP connections to anywhere as authorized by the AAA server. Even though it appears that the aaa commands let the PIX Firewall set security policy, the authentication server actually does the work to decide which users are authenticated and what services they can access when authentication is permitted. |
static (inside, outside) 204.31.19.0 192.168.3.0 netmask 255.255.255.0 conduit permit tcp 204.31.19.0 255.255.255.0 |
The conduit command statement lets users on the Internet send InternetPhone (port h323) requests to users on 192.168.3.x while addressing them as 204.31.19.x. |
static (inside, outside) 204.31.17.29 10.1.1.11 conduit permit tcp host 204.31.17.29 eq 80 any | The static command statement with the conduit command statement establishes an externally visible IP address for Web access (port 80 in the conduit command statement). |
conduit permit udp host 204.31.17.29 eq rpc | Refine the accessibility of the static command by permitting Sun RPC over the UDP portmapper on port 111. Refer to the UNIX /etc/rpc file and the UNIX rpc(3N) command page for more information. Once you create a conduit for RPC, you can use the following command from outside host 204.31.17.17 to track down the activity of a PCNFSD on RPC 150001: rpcinfo -u 204.31.17.29 150001 Another use of RPC is with the following command to see the exports of 204.31.17.29 if you want to allow NFS mounting from outside in. showmount -e 204.31.17.29 Many protocols based on RPC, as well as NFS, are insecure and should be used with caution. Review your security policies carefully before permitting access to RPC. |
conduit permit udp host 204.31.17.29 eq 2049 | |
static (inside, outside) 204.31.17.30 10.1.1.3 | Identify access to the 10.1.1.3 mail server through global address 204.31.17.30. The conduit permits any outside host access to the static via SMTP (port 25). By default, PIXFirewall restricts all access to mail servers to RFC 821 section 4.5.1 commands of DATA, HELO, MAIL, NOOP, QUIT, RCPT, and RSET. This occurs via the Mail Guard service which is set with the following default configuration command: fixup protocol smtp 25 Another aspect of providing access to a mail server is setting being sure that you have a DNS MX record for the static's global address, which outside users access when sending mail to your site. |
conduit permit tcp host 204.31.17.30 eq 113 any | Create access to port 113, the IDENT protocol. If the mail server has to talk to many mail servers on the outside which connect back with the now obsolete and highly criticized IDENT protocol, use this conduit command statement to speed up mail transmission. |
snmp-server host 192.168.3.2 snmp-server location building 42 snmp-server contact polly hedra snmp-server community ohwhatakeyisthee | These commands specify that host 192.168.3.2 can receive SNMP events, which the PIX Firewall sends via syslog. The location and contact commands identify where the host is and who administers it. The community command describes the password in use at the SNMP server for verifying network access with the server. |
telnet 10.1.1.11 255.255.255.255 telnet 192.168.3.0 255.255.255.0 | These commands permit host access to the PIX Firewall console. The first telnet command permits a single host, 10.1.1.11 to access the PIX Firewall console with Telnet. The 255 value in the last octet of the netmask means that only the specified host can access the console. The second telnet command permits PIX Firewall console access from all hosts on the 192.168.3.0 network. The 0 value in the last octet of the netmask permits all hosts in that network access. However, Telnet only permits 16 hosts simultaneous access to the PIX Firewall console over Telnet. |
In Figure 4-4, the PIX Firewall has three interfaces. No address translation is performed between the interfaces.
-Interface Configuration
The network has the following IP addresses and network masks:
Table 4-4 lists the configuration.
| Configuration | Description |
|---|---|
nameif ethernet0 outside security0 nameif ethernet1 inside security100 nameif ethernet2 dmz security50 interface ethernet0 auto interface ethernet1 auto interface ethernet2 auto | PIX Firewall provides nameif command statements for the inside and outside interfaces and the interface command statements for all three interfaces in the default configuration (default configuration command statements are shown in boldface italic screen font). You need to add a nameif command statement for the perimeter interface. |
ip address outside 192.150.50.50 255.255.255.240 ip address inside 192.150.50.98 255.255.255.240 ip address dmz 192.150.50.68 255.255.255.240 | Identify the IP addresses for each of the three interfaces. |
hostname pixfirewall | Specifies the host name for the PIX Firewall. This name appears in the command line prompt. |
arp timeout 14400 | Sets the ARP timeout to 14,400 seconds (four hours). Entries are kept in the ARP table for four hours before they are flushed. Four hours is the standard default value for ARPtimeouts. |
no failover | Disables failover access. |
names | Enables use of text strings instead of IP addresses. This makes your configuration files more readable. |
pager lines 24 | Enables paging so that if when 24 lines of information display, PIX Firewall pauses the listing and prompts you to continue. |
logging buffered debugging | Enable syslog messages, which provide diagnostic information and status for the PIX Firewall. You can view the messages with the showlogging command and clear the message buffer with the clearlogging command. |
rip inside passive rip outside passive no rip inside default no rip outside default | Sets RIP listening attributes. The two rip interface passive commands cause the PIX Firewall to listen to RIP broadcasts on each interface. The no rip interface default commands causes PIX Firewall to not broadcast a default route on either interface. |
route outside 0.0.0.0 0.0.0.0 192.150.50.1 1 | Sets the outside default route to the router attached to the Internet. |
timeout xlate 3:00:00 conn 1:00:00 half-closed0:10:00 udp 0:02:00 timeout rpc 0:10:00 h323 0:05:00 timeout uauth 0:05:00 absolute | Default values for the maximum duration that PIX Firewall resources can remain idle until being freed. |
no snmp-server location no snmp-server contact snmp-server community public | Specifies that SNMP information may be accessed by internal hosts that know the community string, but PIX Firewall does not send trap information to any host. |
mtu outside 1500 mtu inside 1500 mtu dmz 1500 | Sets the maximum transmission unit value for Ethernet access. |
nat (inside) 0 192.150.50.96 255.255.255.240 | Disables NAT (Network Address Translation). |
static (dmz,outside) 192.150.50.70 192.150.50.70 conduit permit tcp host 192.150.50.70 any | Maps access to the 192.150.50.70 host on the dmz interface. The conduit command lets any outside user access the host on any port. |
In Figure 4-5, the PIX Firewall has three interfaces and these attributes:
The network has the following IP addresses and network masks:
| Configuration | Description |
|---|---|
nameif ethernet0 outside security0 nameif ethernet1 inside security100 nameif ethernet2 dmz security50 interface ethernet0 auto interface ethernet1 auto interface ethernet2 auto | PIX Firewall provides nameif command statements for the inside and outside interfaces and the interface command statements for all three interfaces in the default configuration (default configuration command statements are shown in boldface italic screen font). You need to add a nameif command statement for the perimeter interface. |
ip address outside 192.150.50.3 255.255.255.0 ip address inside 10.0.0.3 255.0.0.0 ip address dmz 192.168.0.1 255.255.255.0 | Identify the IP addresses for each of the three interfaces. |
hostname pixfirewall | Specify the host name for the PIX Firewall. This name appears in the command line prompt. |
arp timeout 14400 | Set the ARP timeout to 14,400 seconds (four hours). Entries are kept in the ARP table for four hours before they are flushed. Fourhours is the standard default value for ARPtimeouts. |
no failover | Disable failover access. |
names | Enable use of text strings instead of IP addresses. This makes your configuration files more readable. |
pager lines 24 | Enable paging so that if after 24 lines of information display, PIXFirewall pauses the listing and prompts you to continue. |
logging buffered debugging | Enable syslog messages, which provide diagnostic information and status for the PIX Firewall. You can view the messages with the showlogging command and clear the message buffer with the clearlogging command. |
no rip inside passive no rip outside passive no rip inside default no rip outside default | Disable RIP attributes. |
route outside 0.0.0.0 0.0.0.0 192.150.50.1 1 | Set the outside default route to the router attached to the Internet. |
conduit permit icmp any any | Allow inbound and outbound pings. |
timeout xlate 3:00:00 conn 1:00:00 half-closed0:10:00 udp 0:02:00 timeout rpc 0:10:00 h323 0:05:00 timeout uauth 0:05:00 absolute | Default values for the maximum duration that PIX Firewall resources can remain idle until being freed. |
no snmp-server location no snmp-server contact snmp-server community public | Specify that SNMP information may be accessed by internal hosts that know the community string, but PIX Firewall does not send trap information to any host. |
mtu outside 1500 mtu inside 1500 mtu dmz 1500 | Set the maximum transmission unit value for Ethernet access. |
telnet 10.0.0.100 255.255.255.255 telnet timeout 15 | Give Telnet access to PIX Firewall console to inside host. Use the timeout feature to set the maximum time a Telnet session can be idle before PIX Firewall closes the connection to 15minutes. The default is 5 minutes. |
global (outside) 1 192.150.50.75-192.150.50.85 global (outside) 1 192.150.50.74 global (dmz) 1 192.168.0.10-192.168.0.20 | Create a pool of global addresses for the outside and dmz interfaces. Because there are only 10 outside IP addresses, add a PAT global to handle overflow. The global (dmz) command gives inside users access to the web server on the dmz interface. |
nat (inside) 1 10.0.0.0 255.0.0.0 nat (dmz) 1 192.168.0.0 255.255.255.0 | Let inside users start connections on the dmz and outside interfaces, and let dmz users start connections on the outside interface. |
name 192.168.0.2 webserver | Give the IP address of the web server a label. |
static (dmz,outside) 192.150.50.90 webserver conduit permit tcp host 192.150.50.90 eq 80 any | Let any user on the outside interface access the web server on the dmz interface. |
In Figure 4-6, the PIX Firewall has four interfaces. In this configuration, there is no user authentication and no authorization. NAT (Network Address Translation) is in effect to translate addresses. In this example, users on all interfaces have access to all the servers and hosts on the inside, dmz1, and dmz2 interfaces can start connections.
with NAT
Configuring PIX Firewall for four interfaces requires more attention to detail than other configurations. The most important guidelines to remember are:
The sections that follow provide more information on these guidelines.
To let users on each higher security level interface access servers on each lower security level interface, follow these steps:
Step 1 Letting higher security level interface users access a lower security level interface has two components: you use the nat command to specify from where users start connections, and you use the global command to specify to where access is permitted. You associate the nat and global commands together with the NAT ID, which in this example configuration is 1. The nat command lets users start connections from the specified interface to all lower security interfaces, the global command permits access to translated connections from any higher security level interface.
To let users from the inside interface start connections, use:
nat (inside) 1 0 0
Step 2 To let users on the dmz2 interface start connections, use:
nat (dmz2) 1 0 0
Step 3 To let users on the dmz1 interface start connections, use:
nat (dmz1) 1 0 0
Step 4 To permit access to the dmz2 interface for translated connections, use:
global (dmz2) 1 10.2.1.10-10.2.1.254
Step 5 To permit access to the dmz1 interface for translated connections, use:
global (dmz1) 1 10.1.1.10-10.1.1.254
Step 6 To permit access to the outside interface for translated connections, use:
global (outside) 1 204.31.17.10-204.31.17.254
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To let users on a lower security level interface access a server on a higher security level interface, use the static and conduit commands. The first IP address in the static command is the address users on the lower security level interface use when they want to access the server on the higher security level interface. The second IP address is the actual address of the server.
When you enter the static command statement in your configuration, always specify the security level of the interfaces as (higher,lower) and the IP addresses as lower and higher; for example:
static (inside,dmz1) 10.1.1.7 10.0.1.2
When users on the dmz1 interface access the Telnet server, they use IP address 10.1.1.7.
To let users on each lower security level interface access servers on each higher security level interface, follow these steps:
Step 1 To let users on the outside interface access the mail server on the dmz1 interface, use:
static (dmz1,outside) 204.31.17.5 10.1.1.2 conduit permit tcp host 204.31.17.5 eq smtp any
Step 2 To let users on the outside interface access the web server on the dmz2 interface, use:
static (dmz2,outside) 204.31.17.6 10.2.1.2 conduit permit tcp host 204.31.17.6 eq www any
Step 3 To let users on the outside interface access the Telnet server on the inside interface, use:
static (inside,outside) 204.31.17.7 10.0.1.2 conduit permit tcp host 204.31.17.7 eq telnet any
Step 4 To let users on the dmz1 interface access the web server on the dmz interface, use:
static (dmz2,dmz1) 10.1.1.6 10.2.1.2 conduit permit tcp host 10.1.1.6 eq www any
Step 5 To let users on the dmz1 interface access the Telnet server on the inside interface, use:
static (inside,dmz1) 10.1.1.7 10.0.1.2 conduit permit tcp host 10.1.1.7 eq telnet any
Step 6 To let users on the dmz2 interface access the Telnet server on the inside interface, use:
static (inside,dmz2) 10.2.1.7 10.0.1.2 conduit permit tcp host 10.2.1.7 eq telnet any
All configuration command statements are explained in greater detail in Table 4-6.
Once you sketch out your network and map these steps to your IP addresses and servers, the four interface configuration can become a simpler task.
The addresses used in this configuration are as follows:
In addition static route command statements are required to permit access to the networks that connect to the routers. A static route command statement directs traffic meant for a network to the router on the interface. The format for a static route is shown in the following example:
route inside 10.0.2.0 255.0.0.0 10.0.1.3 1
This command statement instructs the PIX Firewall that when a packet needs to be sent to an address in the 10.0.2.0 network, send it to the router on the inside interface at 10.0.1.3.
Because there are routers on the inside, dmz2, and dmz1 interfaces with two networks connecting to each, six static route command statements are required---two for each interface.
Table 4-6 lists a four interface configuration.
| Configuration | Description |
|---|---|
nameif ethernet0 outside security0 nameif ethernet1 inside security100 nameif ethernet2 dmz1 security40 nameif ethernet3 dmz2 security60 interface ethernet0 auto interface ethernet1 auto interface ethernet2 auto interface ethernet3 auto | PIX Firewall provides nameif command statements for the inside and outside interfaces and the interface command statements for all four interfaces in the default configuration (default configuration command statements are shown in boldface italic screen font). You need to create two nameif command statements for the perimeter interfaces, which in this example are named dmz1 and dmz2. |
ip address outside 204.31.17.1 255.255.255.0 ip address dmz1 10.1.1.1 255.0.0.0 ip address dmz2 10.2.1.1 255.0.0.0 ip address inside 10.0.1.1 255.0.0.0 | Identify the IP address for each interface. |
hostname pixfirewall | Specify the host name for the PIX Firewall. This name appears in the command line prompt. |
arp timeout 14400 | Set the ARP timeout to 14,400 seconds (four hours). This command statement is provided in the default configuration. |
no failover | Disable failover access. |
names | Enable use of text strings instead of IP addresses. This makes your configuration files more readable. |
pager lines 24 | Enable paging so that if after 24 lines of information display, PIXFirewall pauses the listing and prompts you to continue. |
logging buffered debugging | Enable syslog messages, which provide diagnostic information and status for the PIX Firewall. You can view the messages with the showlogging command and clear the message buffer with the clearlogging command. |
no rip inside passive no rip outside passive no rip inside default no rip outside default | Disable RIP attributes. |
route outside 0.0.0.0 0.0.0.0 204.31.17.4 1 | Set the outside default route to the router attached to the Internet. |
conduit permit icmp any any | Allow inbound and outbound pings. |
timeout xlate 3:00:00 conn 1:00:00 half-closed0:10:00 udp 0:02:00 timeout rpc 0:10:00 h323 0:05:00 timeout uauth 0:05:00 absolute | Default values for the maximum duration that PIX Firewall resources can remain idle until being freed. |
no snmp-server location no snmp-server contact snmp-server community public | Specify that SNMP information may be accessed by internal hosts that know the community string, but PIX Firewall does not send trap information to any host. |
mtu outside 1500 mtu inside 1500 mtu dmz1 1500 mtu dmz2 1500 | Set the maximum transmission unit value for Ethernet access. You need to add the MTU command statements for the dmz1 and dmz2 interfaces. |
telnet 10.0.1.4 255.255.255.255 telnet timeout 15 | Give Telnet access to PIX Firewall console to inside host. Use the timeout feature to let Telnet console sessions stay idle up to 15 minutes before PIX Firewall closes the connection. The default is 5 minutes. |
nat (inside) 1 0 0 | Let inside users start connections on all lower security level interfaces: dmz1, dmz2, and the outside. |
nat (dmz2) 1 0 0 | Let dmz2 users start connections on all lower security level interfaces: dmz1 and the outside. |
nat (dmz1) 1 0 0 | Let dmz1 users start connections on all lower security level interfaces, which in this case, is the outside. |
global (dmz2) 1 10.2.1.10-10.2.1.254 | Give access to the dmz2 interface for users on the inside interface. This global command statement lets inside users access the dmz2 web server and provides access to the 10.2.2.0 and 10.2.3.0 networks. |
global (dmz1) 1 10.1.1.10-10.1.1.254 | Give access to the dmz1 interface for users on the inside and dmz2 interfaces. This global command statement lets inside and dmz2 users access the dmz1 mail server and provides access to the 10.1.2.0 and 10.1.3.0 networks. |
global (outside) 1 204.31.17.10-204.31.17.254 global (outside) 1 204.31.17.9 | Create a pool of global addresses for the outside interface to permit users on all other interfaces to access the Internet. Because there are potentially more than 244 users on the 3other interfaces, add a PAT global to handle overflow. |
static (dmz1,outside) 204.31.17.5 10.1.1.2 conduit permit tcp host 204.31.17.5 eq smtp any | Let outside users access the 10.1.1.2 mail server on the dmz1 interface. The outside users access the mail server via global address 204.31.17.5 on the outside interface. The conduit command statement lets users access the mail server on port25(smtp). |
static (dmz2,outside) 204.31.17.6 10.2.1.2 conduit permit tcp host 204.31.17.6 eq www any | Let outside users access the 10.2.1.2 web server on the dmz2 interface. The outside users access the web server via global address 204.31.17.6 on the outside interface. The conduit command statement lets users access the web server on port80(www). |
static (inside,outside) 204.31.17.7 10.0.1.2 conduit permit tcp host 204.31.17.7 eq telnet any | Let outside users access the 10.0.1.2 Telnet server on the inside interface. The outside users access the Telnet server via global address 204.31.17.7 on the outside interface. The conduit command statement lets users access the Telnet server on port23 (telnet). |
static (dmz2,dmz1) 10.1.1.6 10.2.1.2 conduit permit tcp host 10.1.1.6 eq www any | Let dmz1 users access the 10.2.1.2 web server on the dmz2 interface. The dmz1 users access the web server via global address 10.1.1.6 on the dmz1 interface. The conduit command statement lets users access the web server on the WWW port(80). |
static (inside,dmz1) 10.1.1.7 10.0.1.2 conduit permit tcp host 10.1.1.7 eq telnet any | Let dmz1 users access the 10.0.1.2 Telnet server on the inside interface. The dmz1 users access the Telnet server via global address 10.1.1.7 on the dmz1 interface. The conduit command statement lets users access the Telnet server on port 23 (telnet). |
static (inside,dmz2) 10.2.1.7 10.0.1.2 conduit permit tcp host 10.2.1.7 eq telnet any | Let dmz2 users access the 10.0.1.2 Telnet server on the inside interface. The dmz2 users access the Telnet server via global address 10.2.1.7 on the dmz2 interface. The conduit command statement lets users access the Telnet server on port 23 (telnet). |
route dmz1 10.1.2.0 255.0.0.0 10.1.1.3 1 route dmz1 10.1.3.0 255.0.0.0 10.1.1.3 1 | Provide static routes so that packets destined for the 10.1.2.0and 10.1.3.0 networks are sent to the 10.1.1.3 router on the dmz1 interface. |
route dmz2 10.2.2.0 255.0.0.0 10.2.1.3 1 route dmz2 10.2.3.0 255.0.0.0 10.2.1.3 1 | Provide static routes so that packets destined for the 10.2.2.0and 10.2.3.0 networks are sent to the 10.2.1.3 router on the dmz2 interface. |
route inside 10.0.2.0 255.0.0.0 10.0.1.3 1 route inside 10.0.3.0 255.0.0.0 10.0.1.3 1 | Provide static routes so that packets destined for the 10.0.2.0and 10.0.3.0 networks are sent to the 10.0.1.3 router on the inside interface. |
In Figure 4-7, the PIX Firewall has six interfaces. In this configuration, there is no user authentication and no authorization. NAT (Network Address Translation) is in effect to translate addresses. In this example, users on all interfaces have access to all the servers and hosts on the inside, dmz1, dmz2, dmz3, and dmz4 interfaces can start connections.
Configuring PIX Firewall for six interfaces is similar to the four interface example except that you have two more interfaces. The most important guidelines to remember are:
The sections that follow provide more information on these guidelines.
To let users on each higher security level interface access servers on each lower security level interface, follow these steps:
Step 1 Letting higher security level interface users access a lower security level interface has two components: you use the nat command to specify from where users start connections, and you use the global command to specify to where access is permitted. You associate the nat and global commands together with the NAT ID, which in this example configuration is 1. The nat command lets users start connections from the specified interface to all lower security interfaces, the global command permits access to translated connections from any higher security level interface.
nat (inside) 1 0 0
nat (dmz1) 1 0 0
nat (dmz2) 1 0 0
nat (dmz3) 1 0 0
nat (dmz4) 1 0 0
Step 2 Create global pools for the connections to start on each lower level interface:
global (outside) 1 192.150.50.10-192.150.50.254
global (dmz1) 1 10.1.1.10-10.1.1.254
global (dmz2) 1 10.2.1.10-10.2.1.254
global (dmz3) 1 10.3.1.10-10.3.1.254
o
To let users on a lower security level interface access a server on a higher security level interface, use the static and conduit commands. The first IP address in the static command is the address users on the lower security level interface use when they want to access the server on the higher security level interface. The second IP address is the actual address of the server.
When you enter the static command statement in your configuration, always specify the security level of the interfaces as (higher,lower) and the IP addresses as lower and higher; for example:
static (inside,dmz1) 10.1.1.7 10.0.1.2
When users on the dmz1 interface access the Telnet server, they use IP address 10.1.1.7.
To let users on each lower security level interface access servers on each higher security level interface, follow these steps:
Step 1 To let users on the outside interface access the mail server on the dmz1 interface, use:
static (dmz1,outside) 192.150.50.5 10.1.1.2 conduit permit tcp host 192.150.50.5 eq smtp any
Step 2 To let users on the outside interface access the Telnet server on the dmz2 interface, use:
static (dmz2,outside) 192.150.50.6 10.2.1.2 conduit permit tcp host 192.150.50.6 eq telnet any
Step 3 To let users on the dmz1 interface access the Telnet server on the dmz2 interface, use:
static (dmz2,dmz1) 10.1.1.7 10.2.1.2 conduit permit tcp host 10.1.1.7 eq telnet any
All configuration command statements are explained in greater detail in Table 4-7.
Once you sketch out your network and map these steps to your IP addresses and servers, the four-interface configuration can become a simpler task.
The addresses used in this configuration are as follows:
In addition, static route command statements are required to permit access to the networks that connect to the routers. A static route command statement directs traffic meant for a network to the router on the interface. The format for a static route is shown in the following example:
route inside 10.0.2.0 255.255.255.0 10.0.1.4 1
This command statement instructs the PIX Firewall that when a packet needs to be sent to an address in the 10.0.2.0 network, send it to the router on the inside interface at 10.0.0.4.
Because there are routers on the inside, dmz1, and dmz4 interfaces with two networks connecting to each, six static route command statements are required---two for each interface.
Table 4-7 lists a six-interface configuration.
| Configuration | Description |
|---|---|
nameif ethernet0 outside security0 nameif ethernet1 inside security100 nameif ethernet2 dmz1 security20 nameif ethernet3 dmz2 security40 nameif ethernet4 dmz3 security60 nameif ethernet5 dmz4 security80 interface ethernet0 auto interface ethernet1 auto interface ethernet2 auto interface ethernet3 auto interface ethernet4 auto interface ethernet5 auto | PIX Firewall provides nameif command statements for the inside and outside interfaces and the interface command statements for all six interfaces in the default configuration (default configuration command statements are shown in boldface italic screen font). You need to create nameif command statements for the perimeter interfaces. |
ip address outside 192.150.50.1 255.255.255.0 ip address dmz1 10.1.1.1 255.0.0.0 ip address dmz2 10.2.1.1 255.0.0.0 ip address dmz3 10.3.1.1 255.0.0.0 ip address dmz4 10.4.1.1 255.0.0.0 ip address inside 10.0.1.1 255.0.0.0 | Identify the IP address for each interface. |
hostname pixfirewall | Specify the host name for the PIX Firewall. This name appears in the command line prompt. |
arp timeout 14400 | Set the ARP timeout to 14,400 seconds (four hours). This command statement is provided in the default configuration. |
no failover | Disable failover access. |
names | Enable use of text strings instead of IP addresses. This makes your configuration files more readable. |
pager lines 24 | Enable paging so that if after 24 lines of information displays, PIXFirewall pauses the listing and prompts you to continue. |
logging buffered debugging | Enable syslog messages, which provide diagnostic information and status for the PIX Firewall. You can view the messages with the showlogging command and clear the message buffer with the clearlogging command. |
no rip inside passive no rip inside default no rip outside passive no rip outside default no rip dmz1 passive no rip dmz1 default no rip dmz2 passive no rip dmz2 default no rip dmz3 passive no rip dmz3 default no rip dmz4 passive no rip dmz4 default | Disable RIP attributes. Add command statements for the perimeter interfaces. |
route outside 0.0.0.0 0.0.0.0 192.150.50.4 1 | Set the outside default route to the router attached to the Internet. |
route dmz1 10.1.2.0 255.255.255.0 10.1.1.4 1 route dmz1 10.1.3.0 255.255.255.0 10.1.1.4 1 | Provide static routes so that packets destined for the 10.1.2.0and 10.1.3.0 networks are sent to the 10.1.1.4 router on the dmz1 interface. |
route dmz4 10.4.2.0 255.255.255.0 10.4.1.4 1 route dmz4 10.4.3.0 255.255.255.0 10.4.1.4 1 | Provide static routes so that packets destined for the 10.4.2.0and 10.4.3.0 networks are sent to the 10.4.1.4 router on the dmz4 interface. |
route inside 10.0.2.0 255.255.255.0 10.0.1.4 1 route inside 10.0.3.0 255.255.255.0 10.0.1.4 1 | Provide static routes so that packets destined for the 10.1.2.0and 10.0.3.0 networks are sent to the 10.0.1.4 router on the inside interface. |
conduit permit icmp any any | Allow inbound and outbound pings. |
timeout xlate 3:00:00 conn 1:00:00 half-closed0:10:00 udp 0:02:00 timeout rpc 0:10:00 h323 0:05:00 timeout uauth 0:05:00 absolute | Default values for the maximum duration that PIX Firewall resources can remain idle until being freed. |
no snmp-server location no snmp-server contact snmp-server community public | Specify that SNMP information may be accessed by internal hosts that know the community string, but PIX Firewall does not send trap information to any host. |
mtu outside 1500 mtu inside 1500 mtu dmz1 1500 mtu dmz2 1500 mtu dmz3 1500 mtu dmz4 1500 | Set the maximum transmission unit value for Ethernet access. You need to add the MTU command statements for the perimeter interfaces. |
telnet 10.2.1.2 255.255.255.255 telnet timeout 15 | Give Telnet access to PIX Firewall console to users on the Telnet server on dmz2 host. PIX Firewall checks the interface IP address to ensure it is an internal interface. This lets users outside the network Telnet to the server and then access the PIX Firewall console from the server. This is one method that can be used to troubleshoot or administer a PIX Firewall from a remote location. Use the timeout command feature to let Telnet console sessions stay idle up to 15 minutes before PIX Firewall closes the connection. The default is 5 minutes. |
nat (inside) 1 0 0 | Let inside users start connections on all lower security level interfaces: dmz1, dmz2, dmz3, dmz4, and the outside. |
nat (dmz1) 1 0 0 | Let dmz1 users start connections on the lower security level interface: the outside. |
nat (dmz2) 1 0 0 | Let dmz2 users start connections on all lower security level interfaces: dmz1 and the outside. |
nat (dmz3) 1 0 0 | Let dmz3 users start connections on all lower security level interfaces: dmz1, dmz2, and the outside. |
nat (dmz4) 1 0 0 | Let dmz4 users start connections on all lower security level interfaces: dmz1, dmz2, dmz3, and the outside. |
global (outside) 1 192.150.50.10-192.150.50.254 global (outside) 1 192.150.50.9 | Create a pool of global addresses for the outside interface to permit users on all other interfaces to access the Internet. Because there are potentially more than 244 users on the 3other interfaces, add a PAT global to handle overflow. |
global (dmz1) 1 10.1.1.10-10.1.1.254 | Give access to the dmz1 interface for users on the dmz2, dmz3, dmz4, and the inside interfaces. This global command statement lets users on access these interfaces access the dmz1 mail server and provides access to the 10.1.2.0 and 10.1.3.0 networks. |
global (dmz2) 1 10.2.1.10-10.2.1.254 | Give access to the dmz2 interface for users on the inside interface. This global command statement lets inside users on the dmz3, dmz4, and inside access to the Telnet server of dmz2. |
global (dmz3) 1 10.3.1.10-10.3.1.254 | Give access to the dmz3 interface for users on the inside and dmz4 interfaces. |
global (dmz4) 1 10.4.1.10-10.4.1.254 | Give access to the dmz4 interface for users on the inside interface which also permits access to the 10.4.2.0 and 10.4.3.0 networks connected to the 10.4.1.4 router. |
static (dmz1,outside) 192.150.50.6 10.1.1.2 netmask 255.255.255.255 conduit permit tcp host 192.150.50.6 eq smtp any | Give outside users access to the mailserver on the dmz1 interface. |
static (dmz2,outside) 192.159.50.7 10.2.1.2 netmask 255.255.255.255 conduit permit tcp host 192.150.50.7 eq telnet any | Give outside users access to the Telnet server on the dmz2 interface. |
static (dmz2,dmz1) 10.1.1.6 10.2.1.2 netmask 255.255.255.255 conduit permit tcp host 10.1.1.6 eq telnet any | Give dmz1 users access to the Telnet server on the dmz2 interface. |
Posted: Tue Jun 8 20:00:02 PDT 1999
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