Intelligent Services Gateway Configuration Guide, Cisco IOS XE Release 3S
ISG L2 Subscriber Roaming
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ISG L2 Subscriber Roaming

ISG L2 Subscriber Roaming

Subscriber roaming is common in wireless deployments. The ISG L2 Subscriber Roaming feature supports simple IP subscribers connecting to the Cisco Intelligent Services Gateway (ISG) when the subscriber device roams between interfaces, VLANs, or VRFs. This module describes how to configure layer 2 roaming for both simple IPv4 and walk-by subscribers on the ISG.

Information About ISG L2 Subscriber Roaming

ISG Subscriber Roaming

In wireless deployments, most devices used by the customers are handheld devices like mobile phones and tablets. These devices connect themselves to the Cisco ISG via service provider access points. It is highly likely that the same subscriber will be connecting to the ISG via different access points. These access points may or may not be connected to the ISG over the same VLAN or VRF.

A roaming subscriber is one who already has an ISG session through a VLAN or VRF, but after roaming to a different access point, reconnects to the ISG through another VLAN or VRF. This scenario is applicable even if the VLAN or VRF does not change after the subscriber connects to the access point through the ISG via different physical interfaces or sub-interfaces.

Roaming is now automatically enabled on ISG. When a subscriber roams, one of the following two things may happen:
  • The existing session is updated.
  • The existing session is deleted, and the subscriber is re-authenticated, and session recreated based on the subscriber's parameters. When the subscriber reconnects based on deployment configuration parameters, the subscriber may be subjected to re-authentication & may be reconnected to the network.

Roaming Scenarios

Roaming behavior table and deployments:
  • L2-Connected Unclassified MAC
  • L2-Connected (Dual Initiator) DHCP Relay with Unclassified MAC
  • L2-Connected (Dual Initiator) DHCP Server with Unclassified MAC
  • L2-Connected (Hybrid) DHCP Relay or Server with Unclassified MAC

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Most roaming subscribers normally connect to the same AP or physical interface in ISG. However, a few of them also re-connect to APs or physical interfaces different from the one they were connected to earlier.Roaming is currently supported for the following network deployment models:

  • Unclassified MAC or IP subscribers (External DHCP Server)
  • DHCP subscribers (DHCP Relay)
  • DHCP subscribers (DHCP Server)

For the external DHCP server model, ISG sessions are mainly created by unclassified packets, where the session identifiers will be either the IP address or the MAC address depending on whether the sessions are routed or L2-connected.

For the DHCP relay model, ISG sessions are mainly created by DHCP control packets. The ISG relays these packets to the DHCP server and forwards the response received from the server back to the client. Here, the subscriber that has roamed to a new interface may trigger one of the following session initiator packets:
  • Data packet if the subscriber has an existing IP address
  • DHCP Renew control packet if the IP address needs to be renewed
  • DHCP Discover control packet
For the DHCP server model, ISG sessions are mainly created by DHCP control packets. Here, the subscriber that has roamed to a new interface may trigger one of the following packets:
  • Data packet if the subscriber has an existing IP address
  • DHCP Renew control packet if the IP address needs to be renewed
  • DHCP Discover control packet

How to Configure ISG L2 Subscriber Roaming

Enabling Roaming for Simple IP Subscribers

Depending upon network design, subscribers may roam between interfaces, VLANs or VRFs.


Note


Simple IP subscriber roaming is enabled by default. Hence, the ip subscriber l2-roaming command need not be configured to support roaming.

Additional References for ISG L2 Subscriber Roaming

Related Documents

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Master Command List, All Releases

ISG commands

ISG Command Reference

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Feature Information for ISG L2 Subscriber Roaming

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 ISG L2 Subscriber Roaming

Feature Name

Releases

Feature Information

ISG L2 Subscriber Roaming

Cisco IOS XE Release 3.12S

Subscriber roaming is common in wireless deployments. The ISG L2 Subscriber Roaming feature supports simple IP subscribers connecting to the Cisco Intelligent Services Gateway (ISG) when the device roams between interfaces, VLANs or VRFs.

The following command was deprecated: ip subscriber l2-roaming.