Cisco ASA 5500-X Series Next-Generation Firewalls

Introduction

This document provides a sample configuration for PIX 7.1(1) and later of a timeout that is specific to a particular application such as SSH/Telnet/HTTP, as opposed to one that applies to all applications. This configuration example uses the new Modular Policy Framework introduced in PIX 7.0. Refer to Using Modular Policy Framework for more information.

In this sample configuration, the PIX Firewall is configured to allow the workstation (10.77.241.129) to Telnet/SSH/HTTP to the remote server (10.1.1.1) behind the router. A separate connection timeout to Telnet/SSH/HTTP traffic is also configured. All other TCP traffic continues to have the normal connection timeout value associated with timeout conn 1:00:00.

Refer to AASA 8.3 and Later: Set SSH/Telnet/HTTP Connection Timeout using MPF Configuration Example for more information on identical configuration using ASDM with Cisco Adaptive Security Appliance (ASA) with version 8.3 and later.

Prerequisites

Requirements

There are no specific requirements for this document.

Components Used

The information in this document is based on Cisco PIX/ASA Security Appliance Software Version 7.1(1) with Adaptive Security Device Manager (ASDM) 5.1.

The information in this document was created from the devices in a specific lab environment. All of the devices used in this document started with a cleared (default) configuration. If your network is live, make sure that you understand the potential impact of any command.

Conventions

Refer to the Cisco Technical Tips Conventions for more information on document conventions.

Configure

In this section, you are presented with the information to configure the features described in this document.

Note: Use the Command Lookup Tool (registered customers only) in order to obtain more information on the commands used in this section.

Network Diagram

This document uses this network setup:

Note: The IP addressing schemes used in this configuration are not legally routable on the Internet. They are RFC 1918 addresses, which have been used in a lab environment.

Configuration

This document uses this configuration:

Note: These CLI and ASDM configurations are applicable to the Firewall Service Module (FWSM)

CLI Configuration:

PIX Version - 7.1(1)
!
hostname PIX
domain-name Cisco.com
enable password 8Ry2YjIyt7RRXU24 encrypted
names
!
interface Ethernet0
 nameif outside
 security-level 0
 ip address 192.168.200.1 255.255.255.0
!
interface Ethernet1
 nameif inside
 security-level 100
 ip address 10.77.241.142 255.255.255.192
!


access-list inside_nat0_outbound extended permit ip 10.77.241.128 255.255.255.192 any


!--- Define the traffic that has to be matched in the class map.
!--- Telnet is defined in this example. 

access-list outside_mpc_in extended permit tcp host 10.77.241.129 any eq telnet
access-list outside_mpc_in extended permit tcp host 10.77.241.129 any eq ssh
access-list outside_mpc_in extended permit tcp host 10.77.241.129 any eq www
access-list 101 extended permit tcp 10.77.241.128 255.255.255.192 any eq telnet 
access-list 101 extended permit tcp 10.77.241.128 255.255.255.192 any eq ssh
access-list 101 extended permit tcp 10.77.241.128 255.255.255.192 any eq www 

pager lines 24
mtu inside 1500
mtu outside 1500
no failover
no asdm history enable
arp timeout 14400
nat (inside) 0 access-list inside_nat0_outbound
access-group 101 in interface outside

route outside 0.0.0.0 0.0.0.0 192.168.200.2 1
timeout xlate 3:00:00


!--- The default connection timeout value of one hour is applicable to 
!--- all other TCP applications.

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
timeout mgcp-pat 0:05:00 sip 0:30:00 sip_media 0:02:00
timeout uauth 0:05:00 absolute
no snmp-server location
no snmp-server contact
snmp-server enable traps snmp authentication linkup linkdown coldstart
telnet timeout 5
ssh timeout 5
console timeout 0
!


!--- Define the class map telnet in order 
!--- to classify Telnet/ssh/http traffic when you use Modular Policy Framework  
!--- to configure a security feature.
!--- Assign the parameters to be matched by class map.


class-map telnet
 description telnet
  match access-list outside_mpc_in

class-map inspection_default
 match default-inspection-traffic
!
!
policy-map global_policy
 class inspection_default
  inspect dns maximum-length 512
  inspect ftp
  inspect h323 h225
  inspect h323 ras
  inspect netbios
  inspect rsh
  inspect rtsp
  inspect skinny
  inspect esmtp
  inspect sqlnet
  inspect sunrpc
  inspect tftp
  inspect sip
  inspect xdmcp


!--- Use the pre-defined class map telnet in the policy map. 



policy-map telnet


!--- Set the connection timeout under the class mode in which 
!--- the idle TCP (Telnet/ssh/http) connection is disconnected. 
!--- There is a set value of ten minutes in this example. 
!--- The minimum possible value is five minutes.


 class telnet
  set connection timeout tcp 00:10:00 reset
!
!
service-policy global_policy global


!--- Apply the policy-map telnet on the interface.
!--- You can apply the service-policy command to any interface that 
!--- can be defined by the nameif command.

service-policy telnet interface outside
end

ASDM Configuration:

Complete these steps in order to set up TCP connection timeout for Telnet traffic based on access-list that uses ASDM as shown.

Note: Refer to Allowing HTTPS Access for ASDM for basic settings in order to access the PIX/ASA through ASDM.

1. Configure Interfaces

   1. Choose Configuration > Interfaces > Add in order to configure the interfaces Ethernet0 (outside) and Ethernet1 (inside) as shown.

      

      

   2. Click OK.

      

      Equivalent CLI configuration as shown:

      interface Ethernet0
       nameif outside
       security-level 0
       ip address 192.168.200.1 255.255.255.0
      !
      interface Ethernet1
       nameif inside
       security-level 100
       ip address 10.77.241.142 255.255.255.192

2. Configure NAT 0

   1. Choose Configuration > NAT > Translation Exemption Rules > Add in order to allow the traffic from the network 10.77.241.128/26 to access the internet without any translation.

      

   2. Click OK.

      

      Equivalent CLI configuration as shown:

      access-list inside_nat0_outbound extended permit ip 10.77.241.128 255.255.255.192 any
      nat (inside) 0 access-list inside_nat0_outbound

3. Configure ACLs

   Choose Configuration > Security Policy >Access Rules in order to configure the ACLs as shown.

   Click Add in order to configure an ACL 101 that allows the Telnet traffic originated from the network 10.77.241.128/26 to any destination network and apply it for outbound traffic on the outside interface.

   

   Click OK. Similarly for the ssh and http traffic:

   

   

   Equivalent CLI configuration as shown:

   access-list 101 extended permit tcp 10.77.241.128 255.255.255.192 any eq telnet
   access-list 101 extended permit tcp 10.77.241.128 255.255.255.192 any eq ssh
   access-list 101 extended permit tcp 10.77.241.128 255.255.255.192 any eq www
   access-group 101 out interface outside

4. Configure Timeouts

   Choose Configuration > Properties > Timeouts in order to configure the various timeouts. In this scenario, keep the default value for all timeouts.

   

   Equivalent CLI configuration as shown:

   timeout conn 1:00:00 half-closed 0:10:00 udp 0:02:00 icmp 0:00:02

5. Configure Service Policy Rules.

   Choose Configuration > Security Policy > Service Policy Rules > Add in order to configure class map, policy map for the setting up the TCP connection timeout as 10 minutes, and apply the service policy on the outside interface as shown.

   1. Choose the Interface radio button in order to choose outside - (create new service policy), which is to be created, and assign telnet as the policy name.

      

      Click Next.

   2. Create a class map name telnet and choose the Source and Destination IP address (uses ACL) check box in the Traffic match criteria.

      

      Click Next.

   3. Create an ACL in order to match the Telnet traffic originated from the network 10.77.241.128/26 to any destination network and apply it to class telnet.

      

      Click Next. Similarly for the ssh and http traffic:

      

      

   4. Choose Connection Settings in order to set up the TCP Connection Timeout as 10 minutes, and also choose the Send reset to TCP endpoints before timeout check box.

      

   5. Click Finish.

      

   Equivalent CLI configuration as shown:

   access-list outside_mpc_in extended permit tcp host 10.77.241.129  any eq telnet
   access-list outside_mpc_in extended permit tcp host 10.77.241.129 any eq ssh
   access-list outside_mpc_in extended permit tcp host 10.77.241.129 any eq www
   
   class-map telnet
    description telnet
     match access-list outside_mpc_in
   
   policy-map telnet
   class telnet
     set connection timeout tcp 00:10:00 reset
   service-policy telnet interface outside

Ebryonic Timeout

An embryonic connection is the connection that is half open or, for example, the three-way handshake has not been completed for it. It is defined as SYN timeout on the ASA; by default the SYN timeout on the ASA is 30 seconds. This is the way to configure Embryonic Timeout:

access-list emb_map extended permit tcp any any 
 
class-map emb_map
match access-list emb_map
  
policy-map global_policy
class emb_map
set connection timeout embryonic 0:02:00
 
service-policy global_policy global

Verify

Use this section to confirm that your configuration works properly.

The Output Interpreter Tool (registered customers only) (OIT) supports certain show commands. Use the OIT in order to view an analysis of show command output.

Issue the show service-policy interface outside command in order to verify your configurations.

PIX#show service-policy interface outside

   Interface outside:
    Service-policy: http
     Class-map: http
      Set connection policy:
      Set connection timeout policy:
        tcp 0:05:00 reset
      Inspect: http, packet 80, drop 0, reset-drop 0

Issue the show service-policy flow command in order to verify that the particular traffic matches the service policy configurations.

This command output shows an example:

PIX#show service-policy flow tcp host 10.77.241.129 host 10.1.1.2 eq 23

   Global policy:
  Service-policy: global_policy

Interface outside:
  Service-policy: telnet
    Class-map: telnet
      Match: access-list 101
        Access rule: permit tcp 10.77.241.128 255.255.255.192 any eq telnet
      Action:
        Input flow:  set connection timeout tcp 0:10:00 reset

Troubleshoot

If you find that the connection timeout does not work with the Modular Policy Framework (MPF), then check the TCP initiation connection. The issue can be a reversal of the source and destination IP address or a misconfigured IP address in the access list does not match in the MPF to set the new timeout value or to change the default timeout for the application. Create an access list entry (source and destination) in accordance with the connection initiation in order to set the connection timeout with MPF.

Related Information

• Cisco PIX 500 Series Security Appliances
• Cisco ASA 5500 Series Adaptive Security Appliances
• Cisco PIX Security Appliance Release Notes
• Cisco PIX Firewall Software
• Cisco Secure PIX Firewall Command References
• Security Product Field Notices (including PIX)
• Requests for Comments (RFCs)
• Technical Support & Documentation - Cisco Systems