Intelligent Services Gateway Configuration Guide, Cisco IOS XE Release 3S

Redirecting Subscriber Traffic Using ISG Layer 4 Redirect

Intelligent Services Gateway (ISG) is a Cisco IOS 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 User Datagram Protocol (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

For the latest feature information and caveats, see 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 for Redirecting ISG Subscriber Traffic" section.

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

Contents

•Prerequisites for Redirecting ISG Subscriber Traffic

•Restrictions for Redirecting ISG Subscriber Traffic

•Information About Redirecting ISG Subscriber Traffic

•How to Configure ISG Layer 4 Redirect

•Configuration Examples for ISG Layer 4 Redirect

•Additional References

•Feature Information for Redirecting ISG Subscriber Traffic

Prerequisites for Redirecting ISG Subscriber Traffic

For information about release and platform support, see the "Feature Information for Redirecting ISG Subscriber Traffic" section.

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 either applied on a session or a TC on the session.

In Cisco IOS XE software, access lists cannot be configured as match criteria in an ISG Layer 4 redirect configuration. As an alternative, Layer 4 redirect should be configured in ISG traffic class services.

Information About Redirecting ISG Subscriber Traffic

Before you configure the Layer 4 Redirect feature, you should understand the following concepts:

•Overview of ISG Layer 4 Redirect

•Layer 4 Redirect Applications

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.

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

•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.

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 destination IP address and port to the original packet's source.

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) hotspots, 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.

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

•Configuring Layer 4 Redirection in a Service Policy Map

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

•Verifying ISG Traffic Redirection

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

Configuring Layer 4 Redirection in a Service Policy Map

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

Prerequisites

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.

SUMMARY STEPS

1. enable

2. configure terminal

3. policy-map type service policy-map-name

4. class type traffic class-name

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

DETAILED STEPS

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 user or 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 service profile on the AAA server.

DETAILED STEPS

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 commands can be used in any order.

SUMMARY STEPS

1. enable

2. show redirect translations [ip ip-address]

3. show redirect group [group-name]

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

DETAILED STEPS

Examples

The following is sample output from the show redirect translations command:

Router# show redirect translations ip 10.53.0.2

Destination IP/port    Server IP/port         Prot  In Flags  Out Flags  Timestamp

172.20.0.2       23     10.2.36.253      23     TCP   none      none       May 08 2003 
12:37:10

The following is sample output from the show subscriber session command. This output 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 session command 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: FastEthernet0/0.505

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: FastEthernet0/0.505, Active Time = 42 minutes, 54 seconds

Configuration Examples for ISG Layer 4 Redirect

This section contains the following examples:

•Redirecting Unauthenticated Subscriber Traffic: Example

•Redirecting Unauthorized Subscriber Traffic: Example

•Initial Redirection: Example

•Periodic Redirection: Example

•Redirecting DNS Traffic: Example

Redirecting Unauthenticated Subscriber Traffic: Example

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 BLIND-RDT

!

 class type control always event account-logon

  1 authenticate aaa list AUTH-LIST

  2 service-policy type service unapply BLIND-RDT

policy-map type service BLIND-RDT

 class type traffic CLASS-ALL

  redirect to group PORTAL

!

redirect server-group PORTAL

server ip 10.2.36.253 port 80

Redirecting Unauthorized Subscriber Traffic: Example

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 in to the service, the traffic is no longer redirected. When the subscriber logs out of 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

Initial Redirection: Example

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

Periodic Redirection: Example

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

Redirecting DNS Traffic: Example

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

The following sections provide references related to the ISG Layer 4 Redirect feature.

Related Documents

Technical Assistance

Feature Information for Redirecting ISG Subscriber Traffic

Table 1 lists the features in this module and provides links to specific configuration information. For information on a feature in this technology that is not documented here, see the Cisco IOS XE Release ISG Configuration Guide Roadmap.

Use Cisco Feature Navigator to find information about platform support and software image support. Cisco Feature Navigator enables you to determine which Cisco IOS XE software images support a specific software release, feature set, or platform. To access Cisco Feature Navigator, go to http://www.cisco.com/go/cfn. An account on Cisco.com is not required.

Note Table 1 lists only the Cisco IOS XE software release that introduced support for a given feature in a given Cisco IOS XE software release train. Unless noted otherwise, subsequent releases of that Cisco IOS XE software release train also support that feature.

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Any Internet Protocol (IP) addresses and phone numbers used in this document are not intended to be actual addresses and phone numbers. Any examples, command display output, network topology diagrams, and other figures included in the document are shown for illustrative purposes only. Any use of actual IP addresses or phone numbers in illustrative content is unintentional and coincidental.

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