Basic ASA Configuration
Before dealing with any specific configuration procedure for the Adaptive Security Appliance (ASA), you need to understand a set of basic concepts. Example 3-1 shows a summary of the boot process for an ASA 5505 appliance whose factory settings have not been changed yet. Following a successful load of the OS image, a prompt offering an interactive preconfiguration of the device using menus is presented. You do not need to analyze this option because it provides little flexibility.
The initial prompt after boot completion is ciscoasa>, in which ciscoasa is the default hostname for the equipment. The symbol > characterizes that the EXEC or nonprivileged mode is in place, meaning that a limited set of tasks can be accomplished.
The use of the question mark (?), as illustrated in Example 3-2, shows the available commands in a given CLI mode. Typing ? after a command, such as show ?, displays the supported parameters for this command. This CLI help is useful, quickly becoming part of everyday life for anyone who works with Cisco equipment.
Example 3-1. Summary Boot Sequence for ASA
Evaluating BIOS Options ... Launch BIOS Extension to setup ROMMON Cisco Systems ROMMON Version (1.0(12)6) #0: Mon Aug 21 19:34:06 PDT 2006 Platform ASA5505 Use BREAK or ESC to interrupt boot. Use SPACE to begin boot immediately. Launching BootLoader... Boot configuration file contains 1 entry. Loading disk0:/asa821-k8.bin... Booting... Platform ASA5505 Loading... [output suppressed] This platform has an ASA 5505Security Plus license. Encryption hardware device : Cisco ASA-5505 on-board accelerator (revision 0x0) Boot microcode : CN1000-MC-BOOT-2.00 SSL/IKE microcode: CNLite-MC-SSLm-PLUS-2.03 IPSec microcode : CNlite-MC-IPSECm-MAIN-2.04 Cisco Adaptive Security Appliance Software Version 8.2(1) [output suppressed] Cryptochecksum (changed): d41d8cd9 8f00b204 e9800998 ecf8427e Pre-configure Firewall now through interactive prompts [yes]? No Type help or '?' for a list of available commands. ciscoasa>
Example 3-2. Commands Available on ASA exec (Nonprivileged) Mode
! Displaying all the commands available on the EXEC mode with a "?" ciscoasa> ? clear Reset functions enable Turn on privileged commands exit Exit from the EXEC help Interactive help for commands login Log in as a particular user logout Exit from the EXEC no Negate a command or set its defaults ping Send echo messages quit Exit from the EXEC show Show running system information traceroute Trace route to destination ! ! Viewing available options for the show command (while on EXEC mode) ciscoasa> show ? checksum Display configuration information cryptochecksum curpriv Display current privilege level disk0: Display information about disk0: file system flash: Display information about flash: file system history Display the session command history inventory Show all inventory information for all slots power Power attributes version Display system software version
Example 3-3 displays summary information obtained with the show version command. The data returned after its execution includes OS version and hardware components, licensed features, the serial number, and even the uptime since the last reboot.
The enable command with a BLANK password (for a device with no initial configuration) provides access to the privileged mode, recognized by the symbol # after the device hostname. This is illustrated in Example 3-4, which also shows the access to config mode through the configure terminal command. Some of the specific config modes (aaa, interface, ip, router, and so on) are included in the example.
Example 3-3. Sample show version Command for ASA
! Displaying basic information about device hardware and software ciscoasa>show version Cisco Adaptive Security Appliance Software Version 8.2(1) Device Manager Version 6.2(1) Compiled on Tue 05-May-09 22:45 by builders System image file is "disk0:/asa821-k8.bin" Config file at boot was "startup-config" ciscoasa up 17 mins 10 secs Hardware: ASA5505, 256 MB RAM, CPU Geode 500 MHz Internal ATA Compact Flash, 128MB BIOS Flash M50FW080 @ 0xffe00000, 1024KB [output suppressed] Licensed features for this platform: Maximum Physical Interfaces: 8 VLANs : 20, DMZ Unrestricted Inside Hosts : Unlimited Failover : Active/Standby VPN-DES : Enabled VPN-3DES-AES : Enabled SSL VPN Peers : 10 Total VPN Peers : 25 Dual ISPs : Enabled VLAN Trunk Ports : 8 [output suppressed] Total UC Proxy Sessions : 2 Botnet Traffic Filter : Disabled This platform has an ASA 5505 Security Plus license. Serial Number: JMX1144Z1AK Running Activation Key: 0x62306449 0x981618fd 0x2cf05948 0xaf78e074 0x481dedb7 Configuration register is 0x1 Configuration has not been modified since last system restart.
Example 3-4. Moving to Privileged Mode and Viewing Configuration Options
! Moving from EXEC mode to privileged mode (ENABLE) ciscoasa> enable Password: ciscoasa# ! ! Entering configuration (config) mode and displaying available options ciscoasa# configure terminal ciscoasa(config)# ? aaa Enable, disable, or view user authentication, authorization and accounting aaa-server Configure a AAA server group or a AAA server access-group Bind an access-list to an interface to filter traffic access-list Configure an access control element [output suppressed] interface Select an interface to configure ip Configure IP addresses, address pools, IDS, etc ipsec Configure transform-set and IPSec SA lifetime ipv6 Global IPv6 configuration commands [output suppressed] route Configure a static route for an interface route-map Create route-map or enter route-map configuration mode router Enable a routing process routing Configure interface specific unicast routing parameters same-security-traffic Enable same security level interfaces to communicate [output suppressed] wccp Web-Cache Coordination Protocol Commands webvpn Configure the WebVPN service zonelabs-integrity ZoneLabs integrity Firewall Server Configuration ciscoasa(config)#
Example 3-5 illustrates the usage of some CLI output filters (all of them are case-sensitive), which constitutes a useful resource. The first sample uses the | begin filter and instructs the OS to start displaying the line of configuration (or show command) where the keyword being searched (snmp in this case) first appears.
The second exemplified filter uses the | include option, which determines that all lines of the command output that include a match for the searched string should be displayed.
The show running-configuration command displays the active configuration of the device and typically results in a large amount of data. More recent versions of ASA OS enable the output of this command to be broken in configuration blocks related to a specific topic. Example 3-5 illustrates how to employ this resource to restrict the output only to the commands related to timeout information.
Example 3-5. Using CLI Output Filters
! Establishing the point where the display should begin ciscoasa# show running-config | begin snmp no snmp-server location no snmp-server contact snmp-server enable traps snmp authentication linkup linkdown coldstart crypto ipsec security-association lifetime seconds 28800 crypto ipsec security-association lifetime kilobytes 4608000 telnet timeout 5 ! ! Searching for all matches of a certain string (case sensitive) ciscoasa# show running-config | include icmp icmp unreachable rate-limit 1 burst-size 1 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 ! ! Delimiting the section of the running configuration to be displayed ciscoasa# show running-config timeout timeout xlate 3:00:00 timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02 timeout sunrpc 0:10:00 h323 0:05:00 h225 1:00:00 mgcp 0:05:00 mgcp-pat 0:05:00 timeout sip 0:30:00 sip_media 0:02:00 sip-invite 0:03:00 sip-disconnect 0:02:00 timeout sip-provisional-media 0:02:00 uauth 0:05:00 absolute timeout tcp-proxy-reassembly 0:01:00
Basic Configuration for ASA Appliances Other Than 5505
Having powered up an ASA appliance and knowing the basics about command execution modes, it is time to examine some of the fundamental interface configuration tasks:
- Enter interface configuration mode and enable the interface for transmitting and receiving traffic: This mode is indicated by the prompt (config-if)#. At this phase the no shutdown command needs to be issued to remove the interface from the administratively down state. If logical subinterfaces have been configured, the pertinent VLAN information (to match that of the switch to which the firewall connects to) should be added. You can also change the speed and duplex.
- Assign a logical name to the interface: This is accomplished with the nameif command, and the configured name is used in any future reference to the interface. (It is typically easier to remember the logical meaning of an interface than the physical.)
- Assign a security-level to the interface: To reflect the degree of trustworthiness of a given firewall interface, Cisco introduced in the early days of the PIX Firewalls the concept of Security Level. The value of the Security Level (or simply sec-lvl) ranges from 0 to 100, in which the highest possible value, 100, is used for the most trusted network under the firewall control, which is, by default, called inside. Conversely, the name outside is reserved for the less trusted network (frequently the connection to the Internet) and, by default, the value 0 is assigned to its sec-lvl.
- Assign an IP Address to the interface: You can do this either through static or dynamic means using the ip address command.
Figure 3-1 shows the physical and logical reference topologies for the analysis of an ASA 5510 basic setup. Example 3-6 assembles the typical configuration commands, and Example 3-7 displays some commands to obtain information about the ASA interfaces.
Figure 3-1 Sample Topology Using an ASA 5510 Appliance
Example 3-6. Baseline ASA5510 Configuration
! Dedicated Management Interface interface Management0/0 nameif mgmt security-level 100 ip address 192.168.1.11 255.255.255.0 no management-only no shutdown ! ! Physical Interface interface Ethernet0/1 no nameif no security-level no ip address no shutdown ! ! Creating Subinterfaces on interface E0/1 (two logical networks) interface Ethernet0/1.1201 vlan 1201 nameif fw1 security-level 50 ip address 172.16.61.1 255.255.255.0 ! interface Ethernet0/1.1212 vlan 1212 description *** Direct Access to Services Segment *** nameif svcs security-level 99 ip address 172.16.62.171 255.255.255.240
Example 3-7. Viewing Information About ASA Interfaces
! Viewing logical interfaces and correspondent security levels ASA1# show nameif Interface Name Security Ethernet0/1.1201 fw1 50 Ethernet0/1.1212 svcs 99 Management0/0 mgmt 100 ! ! Summary IP Addressing information for the interfaces in use ASA1# show interface ip brief Interface IP-Address OK? Method Status Protocol Ethernet0/1 unassigned YES unset up up Ethernet0/1.1201 172.16.61.1 YES CONFIG up up Ethernet0/1.1212 172.16.62.171 YES CONFIG up up Management0/0 192.168.1.11 YES CONFIG up up ! ! Displaying information about a physical interface ASA1# show interface e0/1 Interface Ethernet0/1 "", is up, line protocol is up Hardware is i82546GB rev03, BW 1000 Mbps, DLY 10 usec Auto-Duplex(Full-duplex), Auto-Speed(1000 Mbps) Available but not configured via nameif MAC address 0014.6a21.b4ef, MTU not set IP address unassigned 0 packets input, 0 bytes, 0 no buffer Received 0 broadcasts, 0 runts, 0 giants 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 L2 decode drops 2 packets output, 128 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 late collisions, 0 deferred 0 input reset drops, 0 output reset drops, 0 tx hangs input queue (blocks free curr/low): hardware (255/255) output queue (blocks free curr/low): hardware (255/253) ! ! Displaying information about a subinterface ASA1# show interface e0/1.1212 Interface Ethernet0/1.1212 "svcs", is up, line protocol is up Hardware is i82546GB rev03, BW 1000 Mbps, DLY 10 usec VLAN identifier 1212 Description: *** Direct Access to Services Segment *** MAC address 0014.6a21.b4ef, MTU 1500 IP address 172.16.62.171, subnet mask 255.255.255.240 Traffic Statistics for "svcs": 0 packets input, 0 bytes 1 packets output, 28 bytes 0 packets dropped ! ! Testing the reachability of local hosts with the ping command ASA1# ping 172.16.61.2 Type escape sequence to abort. Sending 5, 100-byte ICMP Echos to 172.16.61.2, timeout is 2 seconds: !!!!! Success rate is 100 percent (5/5), round-trip min/avg/max = 1/1/1 ms
Basic Configuration for the ASA 5505 Appliance
The ASA 5505, the smallest available model at the time this book was written, comes with an embedded Ethernet switch and has some particularities regarding the initial setup. The other ASA models have only routed interfaces. The operational aspects that deserve special attention are discussed in this section.
Figure 3-2 shows a sample topology that serves as the base for exploring the ASA 5505 platform. Physical interfaces can be configured in either access or trunk mode, as registered in Example 3-8. (This is much like any Cisco Catalyst switch configuration.) Each VLAN allowed on the IEEE 802.1Q trunk must be explicitly defined at the physical interface level (switchport trunk allowed vlan command), and the correspondent logical attributes (nameif, sec-lvl, and so on) are configured under the associated Interface VLAN.
Figure 3-2 Sample Topology Using an ASA 5505 Appliance
Example 3-9 relates to Figure 3-2 and documents the commands employed to verify the existent VLANs and their assigned ports. The typical outputs of the show interface options (physical interface and interface vlan) are registered in this example, which also displays a changed hostname for the appliance (ASA 5505 instead of the default ciscoasa).
Example 3-8. Baseline ASA 5505 Configuration
! Physical Interface operating as an Access Port interface Ethernet0/5 switchport access vlan 100 no shutdown ! ! Physical Interface operating as a 802.1Q (Dot1Q) Trunk Port interface Ethernet0/3 switchport trunk allowed vlan 100,201 switchport mode trunk no shutdown ! ! Logical Interface associated with VLAN 100 interface Vlan100 description *** Management Interface nameif mgmt security-level 100 ip address 192.168.1.2 255.255.255.0 no shutdown ! ! Logical Interface associated with VLAN 201 interface Vlan201 description *** DMZ Network nameif dmz security-level 50 ip address 172.16.201.2 255.255.255.0 no shutdown
Example 3-9. Viewing Information About ASA 5505 Interfaces
! VLAN Assignment on ASA5505 internal switch (L2 information) ASA5505# show switch vlan VLAN Name Status Ports ---- -------------------------------- --------- ----------------------------- 1 - down Et0/0, Et0/1, Et0/2, Et0/4 Et0/6, Et0/7 100 mgmt up Et0/3, Et0/5 201 dmz up Et0/3 ! ! Displaying information about a physical interface on ASA5505 ASA5505# show interface e0/5 Interface Ethernet0/5 "", is up, line protocol is up Hardware is 88E6095, BW 100 Mbps, DLY 100 usec Auto-Duplex(Full-duplex), Auto-Speed(100 Mbps) Available but not configured via nameif MAC address 001e.4a05.2005, MTU not set IP address unassigned 30 packets input, 1920 bytes, 0 no buffer Received 30 broadcasts, 0 runts, 0 giants 0 input errors, 0 CRC, 0 frame, 0 overrun, 0 ignored, 0 abort 0 L2 decode drops 0 switch ingress policy drops 4 packets output, 256 bytes, 0 underruns 0 output errors, 0 collisions, 0 interface resets 0 late collisions, 0 deferred 0 input reset drops, 0 output reset drops 0 rate limit drops 0 switch egress policy drops ! ! Displaying information about a VLAN interface on ASA5505 ASA5505# show interface vlan 201 Interface Vlan201 "dmz", is up, line protocol is up Hardware is EtherSVI, BW 100 Mbps, DLY 100 usec MAC address 001e.4a05.2008, MTU 1500 IP address 172.16.201.2, subnet mask 255.255.255.0 Traffic Statistics for "dmz": 0 packets input, 0 bytes 0 packets output, 0 bytes 0 packets dropped 1 minute input rate 0 pkts/sec, 0 bytes/sec 1 minute output rate 0 pkts/sec, 0 bytes/sec 1 minute drop rate, 0 pkts/sec 5 minute input rate 0 pkts/sec, 0 bytes/sec 5 minute output rate 0 pkts/sec, 0 bytes/sec 5 minute drop rate, 0 pkts/sec