Lab Configuring Access Through the PIX Firewall

Lab 5.5.1 Configuring Access Through the PIX Firewall Complete the following lab exercise to practice what you learned in this chapter. Objectives In this lab exercise you will complete the following tasks: Configure a PIX Firewall to protect an enterprise network from Internet access. Test and verify correct PIX Firewall operation. Configure the PIX Firewall third interface. Test and verify access to the third interface. Visual Objectives The following figure displays the configuration you will complete in this lab exercise. Internet Pod perimeter router 192.168.P.0/24 PIX Firewall e1 inside.1 172.26.26.50.1 e0 outside.2 172.16.P.0/24.2 10.0.P.0 /24.3 e2 dmz.1 Bastion Host web and FTP server Backbone server web, FTP, and TFTP server Inside host web and FTP server Copyright 2001, Cisco Systems, Inc. Cisco Secure PIX Firewall Advanced 2.0 Lab 5.5.1 6-1

Directions Your task in this exercise is to configure the PIX Firewall to work with a perimeter router to protect the campus network from intruders. One PIX Firewall is available for each pod group of two students. Work with your pod members to perform the following steps in this lab exercise: Configure global addresses and NAT for inside and outside interfaces. Test globals and NAT configuration. Configure a static and conduit from the PIX Firewall outside interface to the Windows NT server inside the network. Test and verify correct PIX Firewall operation. Configure the PIX Firewall third interface. Test access to the third interface. Task 1 Configure Global Addresses and NAT for Inside and Outside Interfaces Step 1 Enter the following commands to configure PIX Firewall global address pools and routing: Remove NAT: pixp(config)# no nat (inside) 1 0 0 Step 2 Configure NAT for the internal network s range of IP addresses: pixp(config)# nat (inside) 1 10.0.P.0 255.255.255.0 0 0 Step 3 Display currently configured NAT: pixp(config)# show nat nat (inside)1 10.0.P.0 255.255.255.0 0 0 Step 4 Allow ICMP and ping packets through the PIX Firewall: pixp(config)# conduit permit icmp any any Step 5 Write the current configuration to Flash memory: pixp(config)# write memory Step 6 Write the current configuration to the terminal: pixp(config)# write terminal Step 7 Use the clear xlate command after configuring with the nat and global commands to make the global IP addresses available in the translation table: pixp(config)# clear xlate pixp(config)# show xlate Task 2 Test Globals and NAT Configuration To test the globals and NAT configuration, you must complete the following: 6-2 Cisco Secure PIX Firewall Advanced 2.0 Lab 5.5.1 Copyright 2001, Cisco Systems, Inc.

Step 1 From your Windows command line, ping the perimeter router. C:\> ping 192.168.P.1 Step 2 Step 3 Test the operation of the global and NAT you configured by originating connections through the PIX Firewall. 1. Open a web browser on the Windows NT server. 2. Use the web browser to access the Super Server at IP address 172.26.26.50 by entering http://172.26.26.50. Observe the translation table with the show xlate command. pixp(config)# show xlate Your display should appear similar to the following: Global 192.168.P.20 Local 10.0.P.3 Note that a global address chosen from the low end of the global range has been mapped to your NT laptop. Task 3 Configure a Static and Conduit from the PIX Firewall Outside Interface to the Windows NT Server Inside the Network Step 1 Configure a static translation so that traffic originated from the internal Windows NT server always has the same source address on the outside interface of the PIX Firewall. Test the static and conduit by pinging the Windows NT server from the perimeter router. In a production environment, you should remove the conduit permit icmp any any command to prevent a potential security breach. Use the following commands: Create a static translation from the outside PIX Firewall interface to the internal host, and create a conduit to allow web connections from the outside to your NT server on the inside: pixp(config)# static (inside,outside) 192.168.P.10 10.0.P.3 pixp(config)# conduit permit tcp host 192.168.P.10 eq www any Step 2 (where P = your pod number) Turn on ICMP monitoring at the PIX Firewall: pixp(config)# debug icmp trace ICMP trace on Warning: this may cause problems on busy networks Step 3 Clear the translation table: pixp(config)# clear xlate Step 4 Ping the perimeter router from your Windows NT server to test the translation. Observe the source and destination of the packets at the console of the PIX Firewall. C:\> ping 192.168.P.1 Note the example display for pixp: Copyright 2001, Cisco Systems, Inc. Cisco Secure PIX Firewall Advanced 2.0 Lab 5.5.1 6-3

Inbound ICMP echo reply 192.168.P.1 > 192.168.P.10 > 10.0.P.3 Inbound ICMP echo reply 192.168.P.1 > 192.168.P.10 > 10.0.P.3 Inbound ICMP echo reply 192.168.P.1 > 192.168.P.10 > 10.0.P.3 Inbound ICMP echo reply 192.168.P.1 > 192.168.P.10 > 10.0.P.3 Step 5 Observe the source, destination, and translated addresses on the PIX Firewall console. Ping a peer inside host from your inside host as allowed by the conduit via the static: C:\> ping 192.168.Q.10 Step 6 Step 7 (where Q = peer s pod number) Test web access to another pod s inside host as allowed by the static and conduit configured in this task. 1. Open a web browser on the Windows NT server. 2. Use the web browser to access the inside host of another pod by entering http://192.168.q.10. Turn off debug: pixp(config)#no debug icmp trace Example Configuration Your configuration may look as follows at this point: pixp(config)# write terminal Building configuration... : Saved : PIX Version 5.3(1) nameif ethernet0 outside security0 nameif ethernet1 inside security100 nameif ethernet2 dmz security50 nameif ethernet3 intf3 security15 nameif ethernet4 intf4 security20 nameif ethernet5 intf5 security25 enable password 6RD5.96v/eXN3kta encrypted passwd 2KFQnbNIdI.2KYOU encrypted hostname pixp fixup protocol ftp 21 fixup protocol http 80 fixup protocol smtp 25 fixup protocol h323 1720 fixup protocol rsh 514 fixup protocol sqlnet 1521 fixup protocol sip 5060 names pager lines 24 6-4 Cisco Secure PIX Firewall Advanced 2.0 Lab 5.5.1 Copyright 2001, Cisco Systems, Inc.

no logging timestamp no logging console no logging monitor no logging buffered no logging trap logging facility 20 interface ethernet0 100full interface ethernet1 100full interface ethernet2 100full interface ethernet3 auto shutdown interface ethernet4 auto shutdown interface ethernet5 auto shutdown mtu outside 1500 mtu inside 1500 mtu dmz 1500 mtu intf3 1500 mtu intf4 1500 mtu intf5 1500 ip address outside 192.168.P.2 255.255.255.0 ip address inside 10.0.P.1 255.255.255.0 ip address dmz 172.16.P.1 255.255.255.0 ip address intf3 127.0.0.1 255.255.255.255 ip address intf4 127.0.0.1 255.255.255.255 ip address intf5 127.0.0.1 255.255.255.255 ip audit info action alarm ip audit attack action alarm no failover failover poll 15 failover timeout 0:00:00 failover ip address outside 0.0.0.0 failover ip address inside 0.0.0.0 failover ip address dmz 0.0.0.0 arp timeout 14400 global (outside) 1 192.168.P.20-192.168.P.254 netmask 255.255.255.0 nat (inside) 1 10.0.P.0 255.255.255.0 0 0 static (inside,outside) 192.168.P.10 10.0.P.3 netmask 255.255.255.255 0 0 conduit permit icmp any any conduit permit tcp host 192.168.P.10 eq www any route outside 0.0.0.0 0.0.0.0 192.168.P.1 1 timeout xlate 3:00:00 conn 1:00:00 half-closed 0:10:00 udp 0:02:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 rpc 0:10:00 h323 0:05:00 si p 0:30:00 sip media 0:02:00 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 floodguard enable no sysopt route dnat isakmp identity hostname Copyright 2001, Cisco Systems, Inc. Cisco Secure PIX Firewall Advanced 2.0 Lab 5.5.1 6-5