Redirecting Subscriber Traffic Using ISG Layer 4 Redirect

Intelligent Services Gateway (ISG) is a software feature set that provides a structured framework in which edge devices can deliver flexible and scalable services to subscribers. This module describes how to configure ISG to redirect subscriber traffic by using the ISG Layer 4 Redirect feature. The ISG Layer 4 Redirect feature enables service providers to better control the user experience by allowing subscriber TCP or UDP packets to be redirected to specified servers for appropriate handling. ISG Layer 4 redirection can be used to facilitate subscriber authentication, initial and periodic advertising captivation, redirection of application traffic, and Domain Name System (DNS) redirection.

Finding Feature Information

Your software release may not support all the features documented in this module. For the latest caveats and feature information, see Bug Search Tool and the release notes for your platform and software release. To find information about the features documented in this module, and to see a list of the releases in which each feature is supported, see the feature information table.

Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.

Restrictions for Redirecting ISG Subscriber Traffic

The ISG Layer 4 Redirect feature applies only to TCP or UDP traffic.

A Layer 4 Redirect feature and a traffic-class (TC) service containing a Layer 4 Redirect feature cannot be applied on the same session. A Layer 4 Redirect feature can be applied on a TC in a service, but not directly on a session.

Information About Redirecting ISG Subscriber Traffic

Overview of ISG Layer 4 Redirect

The ISG Layer 4 Redirect feature redirects specified packets to servers that handle the packets in a specified manner. For example, packets sent upstream by unauthorized users can be forwarded to a server that redirects the users to a login page. Similarly, if users try to access a service to which they have not logged in, the packets can be redirected to a server that provides a service login screen.

The Layer 4 Redirect feature supports three types of redirection, which can be applied to subscriber sessions or to flows:

  • Initial redirection—Specified traffic is redirected for a specific duration of the time only, starting from when the feature is applied.

  • Periodic redirection—Specified traffic is periodically redirected. The traffic is redirected for a specified duration of time. The redirection is then suspended for another specified duration. This cycle is repeated. During periodic redirect, all new TCP connections are redirected until the duration of the redirect is over. After that time any new incoming TCP connections will not be redirected. However, all existing TCP connections that were initiated during this redirection will still be redirected so as not to break the connections.

  • Permanent redirection—Specified traffic is redirected to the specified server all the time.

A redirect server can be any server that is programmed to respond to the redirected packets. If ISG is used with a web portal, unauthenticated subscribers can be sent automatically to a login page when they start a browser session. Web portal applications can also redirect to service login pages, advertising pages, and message pages.

Redirected packets are sent to an individual redirect server or redirect server group that consists of one or more servers. ISG selects one server from the group on a rotating basis to receive the redirected packets.

When traffic is redirected, ISG modifies the destination IP address and TCP port of upstream packets to reflect the destination server. For downstream packets, ISG changes the source IP address and port to the original packet’s destination.

When traffic is selected by a policy map that includes a redirection command, packets are fed back into the policy map classification scheme for a second service selection. The modified IP headers can be subject to different classification criteria. For example, if two class maps exist, each with different redirection commands, packets could be redirected, selected by the first class map, and redirected a second time. To avoid this situation, configure traffic class maps so that two consecutive redirections cannot be applied to the same packet.

Layer 4 Redirect Applications

The Layer 4 Redirect feature supports the following applications:

  • TCP redirection for unauthenticated users and unauthorized services—HTTP traffic from subscribers can be redirected to a web dashboard where the subscribers can log in so that authentication and authorization can be performed.

  • Initial and periodic redirection for advertising captivation—Subscriber traffic can be redirected to a sponsor’s web page for a brief period of time at the start of the session or periodically throughout the session.

  • Redirection of application traffic—Application traffic from a subscriber can be redirected so as to provide value-added services. For example, a subscriber’s Simple Mail Transfer Protocol (SMTP) traffic can be redirected to a local mail server that can function as a forwarding agent for the mail.

  • DNS redirection—DNS queries may be redirected to a local DNS server. In some deployments, such as public wireless LAN (PWLAN) hot spots, subscribers may have a static DNS server addresses, which may not be reachable at certain locations. Redirecting DNS queries to a local DNS server allows applications to work properly without requiring reconfiguration.

HA Support for Layer 4 Redirect

The SSO and In ISSU feature provides high availability (HA) support for the ISG Layer 4 Redirect feature. Layer 4 redirect includes the selected service group in its checkpointed data during the initial session and bulk synchronization. The standby processor uses the service group instead of selecting a new one.

Because Layer 4 redirect translations are maintained on the forwarding processor, the translation entries and associated timers are preserved after a route processor stateful switchover (SSO) or In Service Software Upgrade (ISSU) event. The entries are re-created, however, on the new active processor after a forwarding processor switchover.

For information about configuring HA on the ISG router, see the High Availability Configuration Guide, Cisco IOS XE Release 3S.

How to Configure ISG Layer 4 Redirect

There are three ways to apply Layer 4 redirection to sessions. One way is to configure redirection directly on a physical main interface or logical subinterface. A second way is to configure a service profile or service policy map with the Layer 4 redirect attribute in it, and apply that service to the session. A third way is to configure the Layer 4 redirect attribute in the user profile.

The following tasks describe how to configure Layer 4 redirection. The first task is optional. One or more of the next three tasks is required. The last task is optional.

For examples of Layer 4 redirection configuration for specific applications (such as unauthenticated user redirect), see the "Configuration Examples for ISG Layer 4 Redirect" section.

Defining a Redirect Server Group

Perform this task to define a group of one or more servers to which traffic will be redirected. Traffic will be forwarded to servers on a rotating basis.

SUMMARY STEPS

    1.    enable

    2.    configure terminal

    3.    redirect server-group group-name

    4.    server ip ip-address port port-number


DETAILED STEPS
     Command or ActionPurpose
    Step 1 enable


    Example:
    Router> enable
     

    Enables privileged EXEC mode.

    • Enter your password if prompted.

     
    Step 2 configure terminal


    Example:
    Router# configure terminal
     

    Enters global configuration mode.

     
    Step 3 redirect server-group group-name


    Example:
    Router(config)# redirect server-group ADVT-SERVER
     

    Enters redirect server-group configuration mode to define a group of servers in a named redirection server group.

     
    Step 4 server ip ip-address port port-number


    Example:
    Router(config-sg-l4redirect-group)# server ip 10.0.0.1 port 8080
     

    Adds a server to a redirect server group.

    • You can enter this command more than one time to add multiple servers to the server group.

     

    Configuring Layer 4 Redirection in a Service Policy Map

    Perform this task to configure Layer 4 redirection in a service policy map.

    Before You Begin

    The ISG Layer 4 Redirect feature is configured under a traffic class within a service policy map. This task assumes that you have defined the traffic class map. See the "Configuring ISG Subscriber Services" module for more information.


    Note

    Only ISG policing and accounting features can be enabled in conjunction with redirection on the same service policy.

    SUMMARY STEPS

      1.    enable

      2.    configure terminal

      3.    redirect session-limit maximum-number

      4.    policy-map type service policy-map-name

      5.    class type traffic class-name

      6.    redirect to {group server-group-name | ip ip-address [port port-number]}[duration seconds] [frequency seconds]


    DETAILED STEPS
       Command or ActionPurpose
      Step 1 enable


      Example:
      Router> enable
       

      Enables privileged EXEC mode.

      • Enter your password if prompted.

       
      Step 2 configure terminal


      Example:
      Router# configure terminal
       

      Enters global configuration mode.

       
      Step 3 redirect session-limit maximum-number


      Example:
      Router(config)# redirect session-limit 5
       

      (Optional) Sets the maximum number of Layer 4 redirects allowed for each subscriber session.

       
      Step 4 policy-map type service policy-map-name


      Example:
      Router(config)# policy-map type service service1
       

      Enters service policy-map configuration mode to create or modify a service policy map, which is used to define an ISG service.

       
      Step 5 class type traffic class-name


      Example:
      Router(config-service-policymap)# class type traffic class1
       

      (Optional) Enters traffic class map configuration mode to specify a traffic class map that identifies the traffic to which this service applies.

       
      Step 6 redirect to {group server-group-name | ip ip-address [port port-number]}[duration seconds] [frequency seconds]


      Example:
      Router(config-service-policymap-class-traffic)# redirect to ip 10.10.10.10
       

      Redirects traffic to a specified server or server group.

       

      What to Do Next

      You may want to configure a method of activating the service policy map; for example, control policies can be used to activate services. For more information about methods of service activation, see the module "Configuring ISG Subscriber Services".

      Configuring Layer 4 Redirection in a Service Profile or User Profile on the AAA Server

      The Layer 4 Redirect feature can be configured as a Cisco vendor-specific attribute (VSA) in a service profile on an authentication, authorization, and accounting (AAA) server. This attribute can appear more than once in a profile to define different types of redirections for a session and can be used in both user and non-TC service profiles simultaneously.

      SUMMARY STEPS

        1.    Add the Layer 4 Redirect VSA to the user profile or subscriber profile on the AAA server.


      DETAILED STEPS
         Command or ActionPurpose
        Step 1 Add the Layer 4 Redirect VSA to the user profile or subscriber profile on the AAA server.

        Example: 
        Cisco-AVPair = “ip:l4redirect=redirect to {group server-group-name | ip server-ip-address [port port-number]} [duration seconds] [frequency seconds]”
         

        Redirects traffic to a specified server or server group.

         

        What to Do Next

        If you configure ISG Layer 4 redirection in a service profile, you may want to configure a method of activating the service profile; for example, control policies can be used to activate services. For more information about methods of service activation, see the "Configuring ISG Subscriber Services" module.

        Verifying ISG Traffic Redirection

        Perform this task to verify the configuration and operation of ISG Layer 4 traffic redirection. The show commands can be used in any order.

        SUMMARY STEPS

          1.    enable

          2.    show redirect translations [ip ip-address | ipv4 | ipv6] [verbose]

          3.    show redirect group [group-name]

          4.    show subscriber session [detailed] [identifier identifier | uid session-id | username name]


        DETAILED STEPS
           Command or ActionPurpose
          Step 1 enable


          Example:
          Router> enable
           

          Enables privileged EXEC mode.

          • Enter your password if prompted.

           
          Step 2 show redirect translations [ip ip-address | ipv4 | ipv6] [verbose]


          Example:
          Router# show redirect translations ip 10.0.0.0
           

          Displays ISG Layer 4 redirect translations for sessions.

           
          Step 3 show redirect group [group-name]


          Example:
          Router# show redirect group redirect1
           

          Displays information about ISG redirect server groups.

           
          Step 4 show subscriber session [detailed] [identifier identifier | uid session-id | username name]


          Example:
          Router# show subscriber session detailed
           

          Displays ISG subscriber session information.

           

          Examples

          The following is sample output from the show redirect translations command showing the number of active redirect translations: 

          Router# show redirect translations

Maximum allowed number of L4 Redirect translations per session: 5
Destination IP/port    Server IP/port    Prot  In Flags  Out Flags  Timestamp
10.0.1.2        23     10.0.2.2   23     TCP                        Oct 21 2009 11:48:01
10.0.1.2        23     10.0.2.2   23     TCP                        Oct 21 2009 11:48:01
10.0.1.2        23     10.0.2.2   23     TCP                        Oct 21 2009 11:48:01
Total Number of Translations: 3
Highest number of L4 Redirect: 3 by session with source IP 10.0.0.2

          The following sample output from the show subscriber session command shows that Layer 4 redirect is being applied from the service profile: 

          Router# show subscriber session uid 135

Subscriber session handle: 7C000114, state: connected, service: Local Term
Unique Session ID: 135
Identifier: blind-rdt
SIP subscriber access type(s): IP-Interface
Root SIP Handle: CF000020, PID: 73
Current SIP options: Req Fwding/Req Fwded
Session Up-time: 40 minutes, 30 seconds, Last Changed: 40 minutes, 30 seconds
AAA unique ID: 135
Switch handle: F000086
Interface: ATM2/0.53
Policy information:
  Authentication status: unauthen
  Config downloaded for session policy:
  From Access-Type: IP-Interface, Client: SM, Event: Service Selection Request, Service
    Profile name: blind-rdt, 2 references 
      username             "blind-rdt"
      l4redirect           "redirect to group sesm-grp"
  Rules, actions and conditions executed:
    subscriber rule-map blind-rdt
      condition always event session-start
        action 1 service-policy type service name blind-rdt
Session inbound features:
 Feature: Layer 4 Redirect
  Rule  Cfg  Definition
  #1    SVC  Redirect to group sesm-grp  !! applied redirect
Configuration sources associated with this session:
Service: blind-rdt, Active Time = 40 minutes, 32 seconds
Interface: ATM2/0.53, Active Time = 40 minutes, 32 seconds

          The following is sample output from the show subscriber sessioncommand for a session in which the Layer 4 redirection is applied on the interface: 

          Router# show subscriber session uid 133

Subscriber session handle: D7000110, state: connected, service: Local Term
Unique Session ID: 133
Identifier: 
SIP subscriber access type(s): IP-Interface
Root SIP Handle: 1E, PID: 73
Current SIP options: Req Fwding/Req Fwded
Session Up-time: 42 minutes, 54 seconds, Last Changed: 42 minutes, 54 seconds
AAA unique ID: 133
Switch handle: 17000084
Interface: FastEthernet0/0/0.505
Policy information:
  Authentication status: unauthen
Session inbound features:
 Feature: Layer 4 Redirect
  Rule  Cfg  Definition
  #1    INT  Redirect to group sesm-grp 
Configuration sources associated with this session:
Interface: FastEthernet0/0/0.505, Active Time = 42 minutes, 54 seconds

          Configuration Examples for ISG Layer 4 Redirect

          Example: Redirecting Unauthenticated Subscriber Traffic

          In the following example, Layer 4 redirection is configured in the service policy map “BLIND-RDT.” This policy is applied to all sessions at session start and redirects subscriber TCP traffic to the server group called “PORTAL.” At account login the subscriber is authenticated and the redirection is not applied. 

          Service-policy type control DEFAULT-IP-POLICY
policy-map type control DEFAULT-IP-POLICY
 class type control always event session-start
  1 service-policy type service name BLIND-RDT
!
 class type control always event account-logon
  1 authenticate aaa list AUTH-LIST
  2 service-policy type service unapply name BLIND-RDT
policy-map type service BLIND-RDT
 class type traffic CLASS-ALL
  redirect to group PORTAL
!
redirect server-group PORTAL
 server ip 2001:ABCD:14::6, Port 8000

          Example: Redirecting Unauthorized Subscriber Traffic

          The following example shows the configuration of redirection for unauthorized subscribers. If the subscriber is not logged into the service called “svc,” traffic that matches “svc” is redirected to the server group “PORTAL.” Once the subscriber logs on to the service, the traffic is no longer redirected. When the subscriber logs off the service, redirection is applied again. 

          service-policy type control THE_RULE
!
class-map type traffic match-any CLASS-ALL
!
class-map type traffic match-any CLASS-100_110
 match access-group input 100 
 match access-group output 110
!
policy-map type service blind-rdt
 class type traffic CLASS-ALL
  redirect to group PORTAL
!
policy-map type service svc-rdt
 class type traffic CLASS-ALL
  redirect to group PORTAL
!
policy-map type service svc
 class type traffic CLASS-100_110
 class type traffic default in-out
  drop
          policy-map type control THE_RULE
 class type control alwyas event account-logon
  1 authenticate
  2 service-policy type service name svc-rdt
 class type control cond-svc-logon event service-start
  1 service-policy type service unapply name svc-rdt
  2 service-policy type service identifier service-name
 class type control cond-svc-logon event service-stop
  1 service-policy type service unapply name svc
  2 service-policy type service name svc-rdt
 !
class-map type control match-all cond-svc-logon
 match identifier service-name svc 
!
redirect server-group PORTAL
 server ip 10.2.36.253 port 80

          Example: Initial ISG Redirection

          The following example shows ISG configured to redirect the Layer 4 traffic of all subscribers to a server group called “ADVT” for the initial 60 seconds of the session. After the initial 60 seconds, ISG will stop redirecting the traffic for the rest of the lifetime of the session. 

          service-policy type control initial-rdt
policy-map type control intial-rdt
 class type control always event session-start
  1 service-policy type service name initial-rdt-profile
 !
policy-map type service initial-rdt-profile
 class type traffic CLASS-ALL
  redirect to group ADVT duration 60

          Example: Periodic ISG Redirection

          The following example shows how to redirect all subscriber traffic for a period of 60 seconds every 3600 seconds: 

          service-policy control periodic-rdt session-start
!
policy-map type control periodic-rdt
 class type control always event session-start
  1 service-policy service periodic-rdt-profile
 !
policy-map type service periodic-rdt-profile
 redirect to group ADVT duration 60 frequency 3600

          Example: Redirecting DNS Traffic

          The following example shows how to redirect all subscriber DNS packets to the server group “DNS-server:” 

          service-policy type control DNS-rdt

policy-map type control DNS-rdt
 class type control event session-start
  1 service-policy type service name DNS-rdt-profile
  !
policy-map type service DNS-rdt-profile
 class type traffic CLASS-ALL
  redirect to group DNS-server

          Additional References

          Related Documents

          Related Topic

          Document Title

          Cisco IOS commands

          Cisco IOS Master Commands List, All Releases

          ISG commands

          Cisco IOS Intelligent Services Gateway Command Reference

          Configuring ISG subscriber services

          “Configuring ISG Subscriber Services�? module in this guide

          HA commands

          Cisco IOS High Availability Command Reference

          HA configuration

          High Availability Configuration Guide

          Technical Assistance

          Description

          Link

          The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

          http:/​/​www.cisco.com/​cisco/​web/​support/​index.html

          Feature Information for Redirecting ISG Subscriber Traffic

          The following table provides release information about the feature or features described in this module. This table lists only the software release that introduced support for a given feature in a given software release train. Unless noted otherwise, subsequent releases of that software release train also support that feature.

          Use Cisco Feature Navigator to find information about platform support and Cisco software image support. To access Cisco Feature Navigator, go to www.cisco.com/​go/​cfn. An account on Cisco.com is not required.
          Table 1 Feature Information for Redirecting ISG Subscriber Traffic

          Feature Name

          Releases

          Feature Information

          ISG: Flow Control: Flow Redirect

          Cisco IOS XE Release 2.2

          The ISG Layer 4 Redirect feature enables service providers to better control the user experience by allowing subscriber TCP or UDP packets to be redirected to specified servers for appropriate handling. ISG Layer 4 redirection can be applied to individual subscriber sessions or flows.

          Parameterization for ACL and Layer 4 Redirect

          Cisco IOS XE Release 2.4

          The Parameterization for ACL and Layer 4 Redirect feature provides parameterization enhancements for access control lists and Layer 4 redirect.

          ISG: IPv6 Support phase II

          Cisco IOS XE Release 3.5S

          IPv6 support was added for the Layer 4 Redirect feature.

          The following commands were introduced or modified: redirect session-limit, redirect to, server ip, show redirect group, show redirect translations.

          ISG: Flow Control: SSO/ISSU

          Cisco IOS XE Release 3.5S

          HA support was added for ISG features including the Layer 4 Redirect feature.