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Overview

E-series routers support the following types of dynamic interfaces:

Before you begin configuring dynamic interfaces, review the following concepts, described in this section:

Dynamic Interfaces

Although dynamic interfaces are created transparently, it is helpful to understand how dynamic interfaces differ from static interfaces.

A dynamic interface is created through some external event, typically through the receipt of data over a lower-layer link, such as an ATM virtual circuit (VC). Each layer of a static interface is created and configured through an existing configuration mechanism such as the command-line interface (CLI) or Simple Network Management Protocol (SNMP). In contrast, the layers of a dynamic interface are created based on the packets received on the link and can be configured through any one of the following:

Unlike static interfaces, dynamic interfaces are not restored through nonvolatile storage (NVS) after a reboot.

Autodetection

The router performs a process called autodetection, also referred to as autosensing, to determine the layers of each dynamic interface. Autodetection is done when the router conditionally constructs interface layers based on the encapsulation type of the incoming packet.

Unlike static interfaces, which always allocate system resources upon creation, autodetection only uses system resources on demand based on what is detected in the incoming packet. Static interfaces always consume system resources, even when the interface is quiescent. Dynamic interfaces, however, are created as a result of traffic on the interface. Dynamic interfaces may also be dynamically deleted without your intervention, thereby allowing any consumed system resources to be returned.

RADIUS Authentication

RADIUS helps protect your network against unauthorized access. To accomplish this, RADIUS clients running on your router send authentication requests to a central RADIUS server. You can configure dynamic interfaces through RADIUS authentication.

When a packet is received, the authenticating interface, either PPP or ATM 1483, establishes a session with RADIUS and passes the username and password to the RADIUS server. For dynamic IPoA or dynamic bridged Ethernet, the RADIUS username and password are obtained from the information specified by the subscriber command. The RADIUS server returns a grant or deny indication. If authentication is granted, the RADIUS attributes are returned, a user login is created, and the dynamic interfaces are configured from the RADIUS attributes.

ATM 1483 interfaces may receive configuration data from the RADIUS server in the form of traffic-shaping parameters.

Any changes made to a RADIUS configuration for a given dynamic interface do not take effect until an existing dynamic interface configured from this RADIUS entry is recreated, that is, deleted and then dynamically created.

Profiles

Dynamic interfaces can also be configured by profiles. A profile is a set of characteristics that act as a pattern. This pattern can then be dynamically assigned to interfaces. By using a profile, you reduce the management of a large number of interfaces by applying a set of characteristics to multiple interfaces.

When you are configuring a large number of interfaces with the same attributes at the higher layers, you can use a profile to factor out all the common attributes of each layer into one place. This action comprises one or more dynamic layers of the interface column. Once you define the static lower layers, a profile is assigned to the highest static layer of the interface column.

Supported Modules

For information about the modules that support dynamic interfaces on ERX-7xx models, ERX-14xx models, and the ERX-310 router, see E-series Module Guide, Appendix A, Module Protocol Support.

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