Intelligent Services Gateway Configuration Guide, Cisco IOS Release 15.2S
Configuring Ambiguous VLAN support for IP sessions over ISG
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Configuring Ambiguous VLAN support for IP sessions over ISG

Ambiguous VLAN Support for IP sessions over ISG

Last Updated: November 29, 2012

The Ambiguous VLAN Support for IP Sessions over ISG feature allows network service providers to define a range or ranges of inner VLANs and create queue-in-queue (QinQ) VLANs on demand. This is done by specifying a range for the inner VLAN tag in the IEEE 802.1Q-in-Q while maintaining a single outer VLAN tag for each subinterface. This module explains the Ambiguous VLAN Support for IP Sessions over ISG feature and how to configure it.

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 at the end of this module.

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

Restrictions for Ambiguous VLAN Support for IP Sessions over ISG

  • Ambiguous VLANs are currently supported only for Inteliigent Services Gateway (ISG) sessions.
  • IP sessions and PPP sessions are not supported on the same ambiguous subinterfaces. Hence, different ranges need to be specified for the outer VLAN tags for both IP sessions and PPP sessions.
  • Only a limited feature set will be applied to each queue-in-queue (QinQ) pair as no subinterfaces are created for each QinQ pair. The available features include those applicable to the ISG session and those applicable to the ambiguous VLAN interface.
  • This feature is restricted to Layer 2 unclassified MAC and DHCP-initiated ISG sessions.
  • IPv6 sessions are not supported.

Information About Configuring Ambiguous VLAN Support for IP Sessions over ISG

Benefits of Ambiguous VLAN Support for IP Sessions over ISG

Ambiguous VLAN implementation for IP sessions in Intelligent Services Gateway (ISG) has the following benefits:

  • The service provider only needs to know the end-user VLAN ranges instead of the individual end-user VLAN IDs.
  • The ambiguous VLAN feature allows the configuration of multiple VLANs under one subinterface which leads to better Interface Descriptor Block (IDB) utilization.

Where to Go Next

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