Command Reference

Syntax Description

accounting	Enable or disable accounting services with authentication server. Use of this command requires that you previously used the aaa-server command to designate an authentication server.
include	Create a new rule with the specified service to include.
exclude	Create an exception to a previously stated rule by excluding the specified service from authentication, authorization, or accounting to the specified host. The exclude parameter improves the former except option by allowing the user to specify a port to exclude to a specific host or hosts.
acctg_service	The accounting service. Accounting is provided for all services or you can limit it to one or more services. Possible values are any, ftp, http, telnet, or protocol/port. Use any to provide accounting for all TCP services. To provide accounting for UDP services, use the protocol/port form. For protocol/port, the TCP protocol appears as 6, the UDP protocol appears as 17, and so on, and port is the TCP or UDP destination port. A port value of 0 (zero) means all ports. For protocols other than TCP and UDP, the port is not applicable and should not be used.
match acl_name	Specify an access-list command statement name.
authentication	Enable or disable user authentication, prompt user for username and password, and verify information with authentication server. When used with the console option, enables or disables authentication service for access to the PIX Firewall console over Telnet or from the Console connector on the PIX Firewall unit. Use of the aaa authentication command requires that you previously used the aaa-server command to designate an authentication server.
authen_service	The application with which a user is accessing a network. Use any, ftp, http, or telnet. The any value enables accounting or authentication for all TCP services. To have users prompted for authentication credentials, they must use FTP, HTTP, or Telnet. (HTTP is the Web and only applies to web browsers that can prompt for a username and password.) If the authentication or authorization server is authenticating services other than FTP, HTTP, or Telnet, using any will not permit those services to authenticate in the firewall. The firewall only knows how to communicate with FTP, HTTP, and Telnet for authentication and authorization. Only set this parameter to a service other than any if the authentication or authorization server is set the same way. Unless you want to temporarily restrict access to a specific service, setting a service in this command can increase system administration work and may cause all connections to fail if the authentication or authorization server is authenticating one service and you set this command to another.
authorization	Enable or disable TACACS+ user authorization for services (PIX Firewall does not support RADIUS authorization). The authentication server determines what services the user is authorized to access.
author_service	The services which require authorization. Use any, ftp, http, telnet, or protocol/port. Services not specified are authorized implicitly. Services specified in the aaa authentication command do not affect the services which require authorization. For protocol/port: protocol—the protocol (6 for TCP, 17 for UDP, 1 for ICMP, and so on). port—the TCP or UDP destination port, or port range. The port can also be the ICMP type; that is, 8 for ICMP echo or ping. A port value of 0 (zero) means all ports. Port ranges only applies to the TCP and UDP protocols, not to ICMP. For protocols other than TCP, UDP, and ICMP the port is not applicable and should not be used. An example port specification follows: aaa authorization include udp/53-1024 inside 0 0 0 0 This example enables authorization for DNS lookups to the inside interface for all clients, and authorizes access to any other services that have ports in the range of 53 to 1024. Note   Specifying a port range may produce unexpected results at the authorization server. PIX Firewall sends the port range to the server as a string with the expectation that the server will parse it out into specific ports. Not all servers do this. In addition, you may want users to be authorized on specific services, which will not occur if a range is accepted.
inbound	Authenticate or authorize inbound connections. Inbound means the connection originates on the outside interface and is being directed to the inside interface.
outbound	Authenticate or authorize outbound connections. Outbound means the connection originates on the inside and is being directed to the outside interface.
if_name	Interface name from which users require authentication. Use if_name in combination with the local_ip address and the foreign_ip address to determine where access is sought and from whom. The local_ip address is always on the highest security level interface and foreign_ip is always on the lowest. See the Examples section for how the if_name affects the use of this command.
local_ip	The IP address of the host or network of hosts that you want to be authenticated or authorized. You can set this address to 0 to mean all hosts and to let the authentication server decide which hosts are authenticated.
local_mask	Network mask of local_ip. Always specify a specific mask value. Use 0 if the IP address is 0. Use 255.255.255.255 for a host.
foreign_ip	The IP address of the hosts you want to access the local_ip address. Use 0 to mean all hosts.
foreign_mask	Network mask of foreign_ip. Always specify a specific mask value. Use 0 if the IP address is 0. Use 255.255.255.255 for a host.
console	Specify that access to the PIX Firewall console require authentication and optionally, log configuration changes to a syslog server. The aaa authentication serial console command lets you require authentication verification to access the PIX Firewall unit's serial console. The serial console options also logs to a syslog server changes made to the configuration from the serial console. Authenticated access to the PIX Firewall console has different types of prompts depending on the option you choose with the aaa authentication [serial | enable | telnet | ssh] console command. While the enable and ssh options allow three tries before stopping with an access denied message, both the serial and telnet options cause the user to be prompted continually until successfully logging in. The serial option requests a username and password before the first command line prompt on the serial console connection. The telnet option forces you to specify a username and password before the first command line prompt of a Telnet console connection. The enable option requests a username and password before accessing privileged mode for serial, Telnet, or SSH connections. The ssh option requests a username and password before the first command line prompt on the SSH console connection. The ssh option allows a maximum of three authentication attempts. Telnet access to the PIX Firewall console is available from any internal interface, and from the outside interface with IPSec configured, and requires previous use of the telnet command. SSH access to the PIX Firewall console is also available from any interface without IPSec configured, and requires previous use of the ssh command. The new ssh option specifies the group of AAA servers to be used for SSH user authentication. The authentication protocol and AAA server IP addresses are defined with the aaa-server command statement. Similar to the Telnet model, if an aaa authentication ssh console group_tag command statement is not defined, you can gain access to the PIX Firewall console with the username pix and with the PIX Firewall Telnet password (set with the passwd command). If the aaa command is defined but the SSH authentication requests a timeout, which implies the AAA servers may be down or not available, you can gain access to the PIX Firewall using username pix and the enable password (set with the enable password command). By default, the Telnet password is cisco and the enable password is not set. If the console login request times out, you can gain access to the PIX Firewall from the serial console by entering the pix username and the enable password. The maximum password length for accessing the console is 16 characters.
group_tag	The group tag set with the aaa-server command.

Usage Guidelines

An example is as follows:

show access-list 
access-list mylist permit tcp 10.0.0.0 255.255.255.0 172.23.2.0 255.255.255.0 (hitcnt=0) 
access-list yourlist permit tcp any any (hitcnt=0)
show aaa 
aaa authentication match mylist outbound TACACS+ 
 

Similar to IPSec, the keyword permit means "yes" and deny means "no." Therefore, the following command:

aaa authentication match yourlist outbound tacacs

 

is equal to this command:

aaa authentication include any outbound 0.0.0.0 0.0.0.0 0.0.0.0 0.0.0.0 tacacs

 

The aaa command statement list is order dependent between access_list command statements. If the following command is entered:

aaa authentication match yourlist outbound tacacs

 

after this command:

aaa authentication match mylist outbound TACACS+

 

PIX Firewall tries to find a match in the mylist access-list command statement group before it tries to find a match in the yourlist access-list command statement group.

Old aaa command configuration and functionality stays the same and is not converted to the access_list format. Hybrid configurations; that is, old configurations combined with the new access_list configuration are not recommended.

Usage Notes

aaa authentication include any outbound 0 0 server

aaa authentication exclude outbound perim_net perim_mask server

10. When using HTTP authentication to a site running Microsoft IIS that has "Basic text authentication" or "NT Challenge" enabled, users may be denied access from the Microsoft IIS server. This occurs because the browser appends the string: "Authorization: Basic=Uuhjksdkfhk==" to the HTTP GET commands. This string contains the PIX Firewall authentication credentials.

Windows NT Microsoft IIS servers respond to the credentials and assume that a Windows NT user is trying to access privileged pages on the server.  Unless the PIX Firewall username password combination is exactly the same as a valid Windows NT username and password combination on the Microsoft IIS server, the HTTP GET command is denied.

To solve this problem, PIX Firewall provides the virtual http command which redirects the browser's initial connection to another IP address, authenticates the user, then redirects the browser back to the URL which the user originally requested.

Once authenticated, a user never has to reauthenticate no matter how low the PIX Firewall uauth timeout is set.  This is because the browser caches the "Authorization: Basic=Uuhjksdkfhk==" string in every subsequent connection to that particular site. This can only be cleared when the user exits all instances of Netscape Navigator or Internet Explorer and restarts.  Flushing the cache is of no use.

As long as the user repeatedly browses the Internet, the browser resends the "Authorization: Basic=Uuhjksdkfhk==" string to transparently reauthenticate the user.

11. Multimedia applications such as CU-SeeMe, InternetPhone, MeetingPoint, and MS Netmeeting silently start the HTTP service before an H.323 session is established from the inside to the outside.

To avoid interfering with these applications, do not enter blanket outgoing AAA command statements for all challenged ports such as using the any option. Be selective with which ports and addresses you use to challenge HTTP, and when to set user authentication timeouts to a higher timeout value. If interfered with, the multimedia programs may fail on the PC and may even crash the PC after establishing outgoing sessions from the inside.

aaa authentication include any outbound 172.31.0.0 255.255.0.0 0.0.0.0 0.0.0.0 
tacacs+

aaa authentication exclude telnet outbound 172.31.38.0 255.255.255.0 0.0.0.0 0.0.0.0 
tacacs+

2. The following examples demonstrate ways to use the if_name parameter. The PIX Firewall has an inside network of 192.168.1.0, an outside network of 209.165.201.0 (subnet mask 255.255.255.224), and a perimeter network of 209.165.202.128 (subnet mask 255.255.255.224).

This example enables authentication for connections originated from the inside network to the outside network:

aaa authentication include any outbound 192.168.1.0 255.255.255.0 209.165.201.0 
255.255.255.224 tacacs+ 

This example enables authentication for connections originated from the inside network to the perimeter network:

aaa authentication include any outbound 192.168.1.0 255.255.255.0 209.165.202.128 
255.255.255.224 tacacs+

This example enables authentication for connections originated from the outside network to the inside network:

aaa authentication include any inbound 192.168.1.0 255.255.255.0 209.165.201.0 
255.255.255.224 tacacs+

This example enables authentication for connections originated from the outside network to the perimeter network:

aaa authentication include any inbound 209.165.201.0 255.255.255.224 209.165.202.128 
255.255.255.224 tacacs+

This example enables authentication for connections originated from the perimeter network to the outside network:

aaa authentication include any perimeter 209.165.202.128 255.255.255.224 
209.165.201.0 255.255.255.224 tacacs+

3. This example specifies that IP addresses 10.0.0.1 through 10.0.0.254 can originate outbound connections and then enables user authentication so that those addresses must enter user credentials to exit the firewall. In this example, the first aaa authentication command permits authentication on FTP, HTTP, or Telnet depending on what the authentication server handles. The second aaa authentication command lets host 10.0.0.42 start outbound connections without being authenticated. This example uses the default authentication group tacacs+:

nat (inside) 1 10.0.0.0 255.255.255.0

aaa authentication include any outbound 0 0 tacacs+

aaa authentication exclude outbound 10.0.0.42 255.255.255.255 tacacs+ any

4. This example permits inbound access to any IP address in the range of 209.165.201.1 through 209.165.201.30 indicated by the 209.165.201.0 network address (subnet mask 255.255.255.224). All services are permitted by the access-list command, and the aaa authentication command permits authentication on FTP, HTTP, or Telnet depending on what the authentication server handles. The authentication server is at IP address 10.16.1.20 on the inside interface:

aaa-server AuthIn protocol tacacs+

aaa-server AuthIn (inside) host 10.16.1.20 thisisakey timeout 20

static (inside,outside) 209.165.201.0 10.16.1.0 netmask 255.255.255.224

access-list acl_out permit tcp 10.16.1.0 255.255.255.0 209.165.201.0 255.255.255.224

access-group acl_out in interface outside

aaa authentication include any inbound 0 0 AuthIn

5. This example enables authorization for DNS lookups from the outside interface:

aaa authorization include udp/53 inbound 0.0.0.0 0.0.0.0

6. This example enables authorization of ICMP echo-reply packets arriving at the inside interface from inside hosts:

 aaa authorization include 1/0 outbound 0.0.0.0 0.0.0.0

This means that users will not be able to ping external hosts if they have not been authenticated using Telnet, HTTP, or FTP.

aaa authorization include 1/8 outbound 0.0.0.0 0.0.0.0 

Syntax Description

group_tag	An alphanumeric string which is the name of the server group. Use the group_tag in the aaa command to associate aaa authentication and aaa accounting command statements to an AAA server.
if_name	The interface name on which the server resides.
host server_ip	The IP address of the TACACS+ or RADIUS server.
key	A case-sensitive, alphanumeric keyword of up to 127 characters that is the same value as the key on the TACACS+ server. Any characters entered past 127 are ignored. The key is used between the client and server for encrypting data between them. The key must be the same on both the client and server systems. Spaces are not permitted in the key, but other special characters are.
timeout seconds	A retransmit timer that specifies the duration that the PIX Firewall retries access four times to the AAA server before choosing the next AAA server. The default is 5 seconds. The maximum time is 30 seconds. For example, if the timeout value is 10 seconds, PIX Firewall retransmits for 10 seconds and if no acknowledgment is received, tries three times more for a total of 40 seconds to retransmit data before the next AAA server is selected.
protocol auth_protocol	The type of AAA server, either tacacs+ or radius.

Usage Guidelines

The aaa-server command lets you specify an AAA server group. PIX Firewall lets you define separate groups of TACACS+ or RADIUS servers for specifying different types of traffic; such as, a TACACS+ server for inbound traffic and another for outbound traffic. Another use is where all outbound HTTP traffic will be authenticated by a TACACS+ server, and all inbound traffic will use RADIUS.

AAA server group are defined by a tag name that directs different types of traffic to each authentication server. If the first authentication server in the list fails, the AAA subsystem fails over to the next server in the tag group. You can have up to 14 tag groups and each group can have up to 14 AAA servers for a total of up to 196 AAA servers.

The aaa command references the tag group.

Note   The previous server type option at the end of the aaa authentication and aaa accounting commands has been replaced with the aaa-server group tag. Backward compatibility with previous versions is maintained by the inclusion of two default protocols for TACACS+ and RADIUS.

If accounting is in effect, the accounting information goes only to the active server.

The default configuration provides these two aaa-server protocols:

aaa-server TACACS+ protocol tacacs+
aaa-server RADIUS protocol radius

Note   If you are upgrading from a previous version of PIX Firewall and have aaa command statements in your configuration, using the default server groups lets you maintain backward compatibility with the aaa command statements in your configuration.

Examples

1. This example uses the default protocol tacacs+ with the aaa commands:

aaa-server TACACS+ (inside) host 10.1.1.10 thekey timeout 20

aaa authentication include any outbound 0 0 0 0 TACACS+

aaa authorization include any outbound 0 0 0 0

aaa accounting include any outbound 0 0 0 0 TACACS+

aaa authentication serial console TACACS+

This example specifies that the authentication server with the IP address 10.1.1.10 resides on the inside interface and is in the default TACACS+ server group. The next three command statements specify that any users starting outbound connections to any foreign host will be authenticated using TACACS+, that the users who are successfully authenticated are authorized to use any service, and that all outbound connection information will be logged in the accounting database. The last command statement specifies that access to the PIX Firewall unit's serial console requires authentication from the TACACS+ server.

2. This example creates the AuthOut and AuthIn server groups for RADIUS authentication and specifies that servers 10.0.1.40, 10.0.1.41, and 10.1.1.2 on the inside interface provide authentication. The servers in the AuthIn group authenticate inbound connections, the AuthOut group authenticates outbound connections:

aaa-server AuthIn protocol radius

aaa-server AuthIn (inside) host 10.0.1.40 ab timeout 20

aaa-server AuthIn (inside) host 10.0.1.41 abc timeout 4

aaa-server AuthOut protocol radius

aaa-server AuthOut (inside) host 10.1.1.2 abc123 timeout 15

aaa authentication include any inbound 0 0 0 0 AuthIn

aaa authentication include any outbound 0 0 0 0 AuthOut

3. This example lists the commands that can be used to establish an Xauth crypto map:

ip address inside 10.0.0.1 255.255.255.0

ip address outside 168.20.1.5 255.255.255.0

ip local pool dealer 10.1.2.1-10.1.2.254

nat (inside) 0 access-list 80

aaa-server TACACS+ host 10.0.0.2 secret123 

crypto ipsec transform-set pc esp-des esp-md5-hmac 

crypto dynamic-map cisco 4 set transform-set pc

crypto map partner-map 20 ipsec-isakmp dynamic cisco

crypto map partner-map client configuration address initiate

crypto map partner-map client authentication TACACS+ 

crypto map partner-map interface outside

isakmp key cisco1234 address 0.0.0.0 netmask 0.0.0.0

isakmp client configuration address-pool local dealer outside

isakmp policy 8 authentication pre-share 

isakmp policy 8 encryption des

isakmp policy 8 hash md5

isakmp policy 8 group 1

isakmp policy 8 lifetime 86400

The aaa-server command is used with the crypto map command to establish an authentication association so that VPN Clients are authenticated when they access the PIX Firewall.

Refer to the IPSec User Guide for the Cisco Secure PIX Firewall Version 5.2 for a description of the crypto and isakmp commands.

Syntax Description

acl_ID	The name associated with a given access list.
in interface	Filter on inbound packets at the given interface.
interface_name	The name of the network interface.

Usage Guidelines

The access-group command binds an access list to an interface. The access list is applied to traffic inbound to an interface. If you enter the permit option in an access-list command statement, the PIX Firewall continues to process the packet. If you enter the deny option in an access-list command statement, PIX Firewall discards the packet and generates the following syslog message:

%PIX-4-106019: IP packet from source_addr to destination_addr, protocol protocol received 
from interface interface_name deny by access-group acl_ID

 

Always use the access-list command with the access-group command.

Note   The use of access-group command overrides the conduit and outbound command statements for the specified interface_name.

The no access-group command unbinds the acl_ID from the interface interface_name.

The show access-group command displays the current access list bound to the interfaces.

The clear access-group command removes all entries from an access list indexed by acl_ID. If acl_ID is not specified, all access-list command statements are removed from the configuration.

Examples

The following example shows use of the access-group command:

static (inside,outside) 209.165.201.3 10.1.1.3

access-list acl_out permit tcp any host 209.165.201.3 eq 80

access-group acl_out in interface outside

 

The static command statement provides a global address of 209.165.201.3 for the web server at 10.1.1.3. The access-list command statement lets any host access the global address using port 80. The access-group command specifies that the access-list command statement applies to traffic entering the outside interface.

Syntax Description

acl_ID	Name of an access list. You can use either a name or number.
deny	When used with the access-group command, the deny option does not allow a packet to traverse the PIX Firewall. By default, PIX Firewall denies all inbound or outbound packets unless you specifically permit access. When used with a crypto map command statement, deny does not select a packet for IPSec protection. The deny option prevents traffic from being protected by IPSec in the context of that particular crypto map entry. In other words, it does not allow the policy as specified in the crypto map command statements to be applied to this traffic.
permit	When used with the access-group command, the permit option selects a packet to traverse the PIX Firewall. By default, PIX Firewall denies all inbound or outbound packets unless you specifically permit access. When used with a crypto map command statement, permit selects a packet for IPSec protection. The permit option causes all IP traffic that matches the specified conditions to be protected by IPSec using the policy described by the corresponding crypto map command statements.
protocol	Name or number of an IP protocol. It can be one of the keywords icmp, ip, tcp, or udp, or an integer in the range 1 to 254 representing an IP protocol number. To match any Internet protocol, including ICMP, TCP, and UDP, use the keyword ip.
source_addr	Address of the network or host from which the packet is being sent. Use this field when an access-list command statement is used in conjunction with an access-group command statement, or with the aaa match access-list command and the aaa authorization command.
source_mask	Netmask bits (mask) to be applied to source_addr, if the source address is for a network mask.
local_addr	Address of the network or host local to the PIX Firewall. Specify a local_addr when the access-list command statement is used in conjunction with a crypto access-list command statement, a nat 0 access-list command statement, or a vpngroup split-tunnel command statement. The local_addr is the address after NAT has been performed.
local_mask	Netmask bits (mask) to be applied to local_addr, if the local address is a network mask.
destination_addr	IP address of the network or host to which the packet is being sent. Specify a destination_addr when the access-list command statement is used in conjunction with an access-group command statement, or with the aaa match access-list command and the aaa authorization command. For inbound connections, destination_addr is the address after NAT has been performed. For outbound connections, destination_addr is the address before NAT has been performed.
destination_mask	Netmask bits (mask) to be applied to destination_addr, if the destination address is a network mask.
remote_addr	IP address of the network or host remote to the PIX Firewall. specify a remote_addr when the access-list command statement is used in conjunction with a crypto access-list command statement, a nat 0 access-list command statement, or a vpngroup split-tunnel command statement.
remote_mask	Netmask bits (mask) to be applied to remote_addr, if the remote address is a network mask
operator	A comparison operand that lets you specify a port or a port range. Use without an operator and port to indicate all ports; for example: access-list acl_out permit tcp any host 209.165.201.1 Use eq and a port to permit or deny access to just that port. For example, use eq ftp to permit or deny access only to FTP: access-list acl_out deny tcp any host 209.165.201.1 eq ftp Use lt and a port to permit or deny access to all ports less than the port you specify. For example, use lt 2025 to permit or deny access to the well known ports (1 to 1024): access-list acl_dmz1 permit tcp any host 192.168.1.1 lt 1025 Use gt and a port to permit or deny access to all ports greater than the port you specify. For example, use gt 42 to permit or deny ports 43 to 65535: access-list acl_dmz1 deny udp any host 192.168.1.2 gt 42 Use neq and a port to permit or deny access to every port except the ports that you specify. For example, use neq 10 to permit or deny ports 1-9 and 11 to 65535: access-list acl_dmz1 deny tcp any host 192.168.1.3 neq 10
operator (continued)	Use range and a port range to permit or deny access to only those ports named in the range. For example, use range 10 1024 to permit or deny access only to ports 10 through 1024. All other ports are unaffected. The use of port ranges can dramatically increase the number of IPSec tunnels. For example, if a port range of 5000 to 65535 is specified for a highly dynamic protocol, up to 60,535 tunnels can be created. access-list acl_dmz1 deny tcp any host 192.168.1.4 range ftp telnet
port	Services you permit or deny access to. Specify services by the port that handles it, such as smtp for port 25, www for port 80, and so on. You can specify ports by either a literal name or a number in the range of 0 to 65535. You can view valid port numbers online at the following site: http://www.isi.edu/in-notes/iana/assignments/port-numbers See "Ports" in "Introduction," for a list of valid port literal names in port ranges; for example, ftp h323. You can also specify numbers.
icmp_type	[Non-IPSec use only]—Permit or deny access to ICMP message types. Refer to Table 5-1 for a list of message types. Omit this option to mean all ICMP types. ICMP message types are not supported for use with IPSec; that is when the access-list command is used in conjunction with the crypto map command, the icmp_type is ignored.

Usage Guidelines

Use the following guidelines for specifying a source, local, or destination address:

• Use a 32-bit quantity in four-part, dotted-decimal format.

• Use the keyword any as an abbreviation for an address and mask of 0.0.0.0 0.0.0.0. This keyword is normally not recommended for use with IPSec.

• Use host address as an abbreviation for a mask of 255.255.255.255.

Use the following guidelines for specifying a network mask:

• Do not specify a mask if the address is for a host; if the destination address is for a host, use the host parameter before the address; for example:

access-list acl_grp permit tcp any host 192.168.1.1 

• If the address is a network address, specify the mask as a 32-bit quantity in four-part, dotted-decimal format. Place zeros in the bit positions you want to ignore.

• Remember that you specify a network mask differently than with the Cisco IOS software access-list command. With PIX Firewall, use 255.0.0.0 for a Class A address, 255.255.0.0 for a Class B address, and 255.255.255.0 for a Class C address. If you are using a subnetted network address, use the appropriate network mask; for example:

access-list acl_grp permit tcp any 209.165.201.0 255.255.255.224

 

If appropriate, after you have defined an access list, bind it to an interface using the access-group command. For IPSec use, bind it with a crypto map command statement. In addition, you can bind an access list with the RADIUS authorization feature (described in the next section). Refer to the IPSec User Guide for the Cisco Secure PIX Firewall Version 5.2 for a description of the crypto command.

The show access-list command lists the access-list command statements in the configuration. The show access-list command also lists a hit count that indicates the number of times an element has been matched during an access-list command search. The clear access-list command removes all access-list command statements from the configuration.

The no access-list command removes an access-list command from the configuration. If you remove all the access-list command statements in an access list group, the no access-list command also removes the corresponding access-group command from the configuration.

Note   The aaa, crypto map, and icmp commands make use of the access-list command statements.

The administrator first defines access lists on the PIX Firewall for each user group. For example, there could be access lists for each department in an organization, sales, marketing, engineering, and so on. The administrator then defines each access list in the group profile in CiscoSecure.

After the PIX Firewall authenticates a user, it can then use the CiscoSecure acl attribute returned by the authentication server to identify an access list for a given user group. To maintain consistency, PIX Firewall also provides the same functionality for TACACS+.

To restrict users in a department to three servers and deny everything else, the access-list command statements are as follows:

access-list eng permit ip any server1 255.255.255.255

access-list eng permit ip any server2 255.255.255.255

access-list eng permit ip any server3 255.255.255.255

access-list eng deny ip any any

 

In this example, the vendor specific attribute string in the CiscoSecure configuration has been set to acl=eng. Use this field in the CiscoSecure configuration to identify the access-list identification name. The PIX Firewall gets the acl=acl_ID from CiscoSecure and extracts the ACL number from the attribute string, which it puts in a user's uauth entry. When a user tries to open a connection, PIX Firewall checks the access list in the user's uauth entry, and depending on the permit or deny status of the access list match, permits or denies the connection. When a connection is denied, PIX Firewall generates a corresponding syslog message. If there is no match, then the implicit rule is to deny.

Because the source IP of a given user can vary depending on where they are logging in from, set the source address in the access-list command statement to any, and the destination address to identify which network services the user is permitted or denied access to. If you want to specify that only users logging in from a given subnet may use the specified services, specify the subnet instead of using any.

Note   An access list used for RADIUS authorization does not require an access-group command to bind the statements to an interface.

There is not a radius option to the aaa authorization command.

Follow these steps to enable RADIUS authorization:

Step 2   Create the access-list command statements to specify what services hosts are authorized to use with RADIUS.

Step 3   Configure the authentication server with the vendor-specific acl=acl_ID identifier to specify the access-list ID.

When the PIX Firewall sends a request to the authentication server, it returns the acl=acl_ID string, which tells PIX Firewall to use the access-list command statements to determine how RADIUS users are authorized.

Usage Notes

%PIX-4-106019: IP packet from source_addr to destination_addr, protocol protocol 
received from interface interface_name deny by access-group acl_ID

If you specify an ICMP message type for use with IPSec, PIX Firewall ignores it. For example:

access-list 10 permit icmp any any echo-reply

 

And IPSec is enabled such that a crypto map command references the acl_name for this access-list command, then the echo-reply ICMP message type is ignored.

Using the access-list Command with IPSec

The access lists themselves are not specific to IPSec. It is the crypto map command statement referencing the specific access list that defines whether IPSec processing is applied to the traffic matching a permit in the access list.

Crypto access lists associated with the IPSec crypto map command statement have these primary functions:

• Select outbound traffic to be protected by IPSec (permit = protect).

• Indicate the data flow to be protected by the new security associations (specified by a single permit entry) when initiating negotiations for IPSec security associations.

• Process inbound traffic to filter out and discard traffic that IPSec protects.

• Determine whether or not to accept requests for IPSec security associations on behalf of the requested data flows when processing IKE negotiation from the IPSec peer. (Negotiation is only done for crypto map command statements with the ipsec-isakmp option.) For a peer's initiated IPSec negotiation to be accepted, it must specify a data flow that is permitted by a crypto access list associated with an ipsec-isakmp crypto map entry.

You can associate a crypto access list with an interface by defining the corresponding crypto map command statement and applying the crypto map set to an interface. Different access lists must be used in different entries of the same crypto map set. However, both inbound and outbound traffic will be evaluated against the same "outbound" IPSec access list. Therefore, the access list's criteria are applied in the forward direction to traffic exiting your PIX Firewall and the reverse direction to traffic entering your PIX Firewall.

If you want certain traffic to receive one combination of IPSec protection (for example, authentication only) and other traffic to receive a different combination of IPSec protection (for example, both authentication and encryption), you need to create two different crypto access lists to define the two different types of traffic. These different access lists are then used in different crypto map entries that specify different IPSec policies.

Cisco recommends that you configure "mirror image" crypto access lists for use by IPSec and that you avoid using the any keyword. See the IPSec User Guide for the Cisco Secure PIX Firewall Version 5.2 for more information.

If you configure multiple statements for a given crypto access list, in general, the first permit statement matched, will be the statement used to determine the scope of the IPSec security association. That is, the IPSec security association will be set up to protect traffic that meets the criteria of the matched statement only. Later, if traffic matches a different permit statement of the crypto access list, a new, separate IPSec security association will be negotiated to protect traffic matching the newly matched access list statement.

Some services such as FTP require two access-list command statements, one for port 10 and another for port 21, to properly encrypt FTP traffic.

Examples

The following example creates a numbered access list that specifies a Class C subnet for the source and a Class C subnet for the destination of IP packets. Because the access-list command is referenced in the crypto map command statement, PIX Firewall encrypts all IP traffic that is exchanged between the source and destination subnets.

access-list 101 permit ip 172.21.3.0 255.255.0.0 172.22.2.0 255.255.0.0

access-group 101 in interface outside

crypto map mymap 10 match address 101

[other crypto map commands]
 

The next example only lets an ICMP message type of echo-reply be permitted into the outside interface:

access-list acl_out permit icmp any any echo-reply

access-group acl_out interface outside

 

Syntax Description

if_name	The internal network interface name in which the foreign_ip overlaps.
dnat_ip	An IP address on the internal network that provides an alternate IP address for the external address that is the same as an address on the internal network.
foreign_ip	IP address on the external network that has the same address as a host on the internal network.
netmask	Network mask applied to both IP addresses. Use 255.255.255.255 for host masks.

Usage Guidelines

The alias command translates one address into another. Use this command to prevent conflicts when you have IP addresses on a network that are the same as those on the Internet or another intranet. You can also use this command to do address translation on a destination address. For example, if a host sends a packet to 209.165.201.1, you can use the alias command to redirect traffic to another address, such as, 209.165.201.30.

Note   You can use the sysopt nodnsalias command to disable inbound embedded DNS A record fixups according to aliases that apply to the A record address and outbound replies.

Note   If the alias command is used with the sysopt ipsec pl-compatible command, a static route command statement must be added for each IP address specified in the alias command statement.

After changing or removing an alias command statement, use the clear xlate command.

There must be an A (address) record in the DNS zone file for the "dnat" address in the alias command.

The alias command has two uses which can be summarized in the following ways of reading an alias command statement:

• If the PIX Firewall gets a packet destined for the dnat_IP_address, send it to the foreign_IP_address.

• If the PIX Firewall gets a DNS packet returned to the PIX Firewall destined for foreign_network_address, alter the DNS packet to change the foreign network address to dnat_network_address.

The no alias command disables a previously set alias command statement. The show alias command displays alias command statements in the configuration. The clear alias command removed all alias commands from the configuration.

The alias command automatically interacts with DNS servers on your network to ensure that domain name access to the aliased IP address is handled transparently.

Note   ActiveX blocking does not occur when users access an IP address referenced by the alias command. ActiveX blocking is set with the filter activex command.

Usage Notes

To access an alias dnat_ip address with static and access-list command statements, specify the dnat_ip address in the access-list command statement as the address from which traffic is permitted from. The following example illustrates this note:

alias (inside) 192.168.201.1 209.165.201.1 255.255.255.255

static (inside,outside) 209.165.201.1 192.168.201.1 netmask 255.255.255.255

access-list acl_out permit tcp host 192.168.201.1 host 209.165.201.1 eq ftp-data

access-group acl_out in interface outside

 

An alias is specified with the inside address 192.168.201.1 mapping to the foreign address 209.165.201.1.

Examples

1. In this example, the inside network contains the IP address 209.165.201.29, which on the Internet belongs to example.com. When inside clients try to access example.com, the packets do not go to the firewall because the client thinks 209.165.201.29 is on the local inside network. To correct this, a net alias is created as follows with the alias command:

alias (inside) 192.168.201.0 209.165.201.0 255.255.255.224

 
show alias

alias 192.168.201.0 205.165.201.0 255.255.255.224

When the inside network client 209.165.201.2 connects to example.com, the DNS response from an external DNS server to the internal client's query would be altered by the PIX Firewall to be 192.168.201.29. If the PIX Firewall uses 209.165.200.225 through 209.165.200.254 as the global pool IP addresses, the packet goes to the PIX Firewall with SRC=209.165.201.2 and DST=209.165.201.29. The PIX Firewall translates the address to SRC=209.165.200.254 and DST=209.165.201.29 on the outside.

2. In the next example, a web server is on the inside at 10.1.1.11 and a static for it at 209.165.201.11. The source host is on the outside with address 209.165.201.7. A DNS server on the outside has a record for www.example.com as follows:

www.example.com.

IN

A

209.165.201.11

The period at the end of the www.example.com. domain name must be included.

The alias command follows:

alias 10.1.1.11 209.165.201.11 255.255.255.255

PIX Firewall doctors the nameserver replies to 10.1.1.11 for inside clients to directly connect to the web server.

The static command statement is as follows:

static (inside,outside) 209.165.201.11 10.1.1.11

The access-list command statement you would expect to use follows:

access-list acl_grp permit tcp host 209.165.201.7 host 209.165.201.11 eq telnet

But with the alias command, use this command:

access-list acl_grp permit tcp host 209.165.201.11 eq telnet host 209.165.201.7

You can test the DNS entry for the host with the following UNIX nslookup command:

nslookup -type=any www.example.com

Syntax Description

if_name	The internal or external interface name specified by the nameif command.
ip_address	Host IP address for the ARP table entry.
mac_address	Hardware MAC address for the ARP table entry; for example, 00e0.1e4e.3d8b.
alias	Make this entry permanent. Alias entries do not time out and are automatically stored in the configuration when you use the write command to store the configuration.
seconds	Duration that an ARP entry can exist in the ARP table before being cleared.

Usage Guidelines

Note   You can use the sysopt noproxyarp command to disable proxy-arps on an interface.

Use the arp command to add an entry for new hosts you add on your network or when you swap an existing host for another. Alternatively, you can wait for the duration specified with the arp timeout command to expire and the ARP table rebuilds itself automatically with the new host information.

The arp timeout command sets the duration that an ARP entry can stay in the PIX Firewall ARP table before expiring. The timer is known as the ARP persistence timer. The default value is
14,400 seconds (4 hours).

The no arp timeout command sets the timer to its default value. The show arp timeout command displays its current value.

Examples

The following examples illustrate use of the arp and arp timeout commands:

arp inside 192.168.0.42 00e0.1e4e.2a7c

arp outside 192.168.0.43 00e0.1e4e.3d8b alias

show arp

outside 192.168.0.43 00e0.1e4e.3d8b alias
inside 192.168.0.42 00e0.1e4e.2a7c
 
clear arp inside 192.168.0.42

 
arp timeout 42

show arp timeout

arp timeout 42 seconds
 
no arp timeout

show arp timeout

arp timeout 14400 seconds

Syntax Description

accept	If a user authentication via Telnet is accepted, display the prompt string.
reject	If a user authentication via Telnet is rejected, display the prompt string.
prompt	The AAA challenge prompt string follows this keyword. This keyword is optional for backward compatibility.
string	A string of up to 235 alphanumeric characters. Special characters should not be used; however, spaces and punctuation characters are permitted. Entering a question mark or pressing the Enter key ends the string. (The question mark appears in the string.)

Usage Guidelines

The auth-prompt command lets you change the AAA challenge text for HTTP, FTP, and Telnet access. This text displays above the username and password prompts that users view when logging in. If you do not use this command, FTP users view FTP authentication,  HTTP users view HTTP Authentication, and challenge text does not appear for Telnet access.

If the user authentication occurs from Telnet, you can use the accept and reject options to display different authentication prompts if the authentication attempt is accepted or rejected by the authentication server.

Note   Microsoft Internet Explorer only displays up to 37 characters in an authentication prompt. Netscape Navigator displays up to 120 characters, and Telnet and FTP display up to 235 characters in an authentication prompt.

Examples

The following example shows how to set the authentication prompt and how users view the prompt:

auth-prompt XYZ Company Firewall Access

 

After this string is added to the configuration, users view:

XYZ Company Firewall Access
User Name:
Password:
 

The prompt keyword can be included or omitted. For example:

auth-prompt prompt Hello There!

 

This command statement is the same as the following:

auth-prompt Hello There!

 

Table 5-3: Privileged Mode Clear Commands

Clear Command	Description	Described on Command Page
clear arp	Clears the ARP table.	arp
clear auth-prompt	Removes an auth-prompt command statement from the configuration.	auth-prompt
clear blocks	Resets the show blocks command statement counters.	show blocks/clear blocks
clear configure	Resets command parameters in the configuration to their default values.	configure
clear flashfs	Clears Flash memory prior to downgrading the PIX Firewall software version.	flashfs
clear local-host	Resets the information displayed for the show local-host command.	local-host (clear and show)
clear passwd	Resets the Telnet password back to "cisco."	passwd
clear traffic	Resets the counters for the show traffic command.	show traffic/clear traffic
clear uauth	Deletes one user's or all users' AAA authorization caches, which forces the user or users to reauthenticate the next time they create a connection.	uauth (clear and show)
clear xlate	Clears the contents of the translation slots.	xlate (clear and show)

Table 5-4: Configuration Mode Clear Commands

Clear Command	Description	Described on Command Page
clear aaa	Remove aaa command statements from the configuration	aaa
clear access-list	Remove access-list command statements from the configuration. This command also stops all traffic through the PIX Firewall on the affected access-list command statements.	access-list
clear access-group	Removes access-group command statements from the configuration.	access-group
clear alias	Removes alias command statements from the configuration.	alias
clear apply	Removes apply command statements from the configuration.	outbound/apply
clear conduit	Removes conduit command statements from the configuration.	conduit
clear dhcpd	Removes dhcpd command statements from the configuration.	dhcpd
clear established	Removes established command statements from the configuration.	established
clear filter	Removes filter command statements from the configuration.	filter
clear fixup	Resets fixup protocol command statements to their default values.	fixup protocol
clear flashfs	Clears Flash memory before downgrading to a previous PIX Firewall version	flashfs
clear global	Removes global command statements from the configuration.	global
clear icmp	Removes icmp command statements from the configuration.	icmp
clear ip	Sets all PIX Firewall interface IP addresses to 127.0.0.1 and stops all traffic.	ip address
clear interface	Clear counters for the show interface command.	interface
clear logging	Clear syslog message queue accumulated by the logging buffered command.	logging
clear names	Removes name command statements from the configuration.	name/names
clear nameif	Reverts nameif command statements to default interface names and security levels.	nameif
clear nat	Removes nat command statements from the configuration.	nat
clear outbound	Removes outbound command statements from the configuration.	outbound/apply
clear rip	Removes rip command statements from the configuration.	rip
clear route	Removes route command statements from the configuration that do not contain the CONNECT keyword.	route
clear snmp-server	Removes snmp-server command statements from the configuration.	snmp-server
clear ssh	Removes ssh command statement from the configuration.	ssh
clear static	Removes static command statements from the configuration.	static
clear sysopt	Removes sysopt command statements from the configuration.	sysopt
clear telnet	Removes telnet command statements from the configuration.	telnet
clear tftp-server	Removes tftp-server command statements from the configuration.	tftp-server
clear timeout	Resets timeout command durations to their default values.	timeout
clear url-cache	Removes url-cache command statements from the configuration.	url-cache
clear url-server	Removes url-server command statements from the configuration.	url-server
clear virtual	Removes virtual command statements from the configuration.	virtual
clear vpdn	Removes vpdn command statements from the configuration.	vpdn

Syntax Description

hh:mm:ss	The current hour:minutes:seconds expressed in 24-hour time; for example, 20:54:00 for 8:54 pm. Zeros can be entered as a single digit; for example, 21:0:0.
month	The current month expressed as the first three characters of the month; for example, apr for April.
day	The current day of the month; for example, 1.
year	The current year expressed as four digits; for example, 2000.

Usage Guidelines