Configuring IPoA Dynamic Interfaces

E-series routers support dynamic IP over ATM (IPoA) interfaces. An IPoA interface is IP over ATM 1483 over ATM AAL5 over ATM. See Figure 24.

An IPoA interface configuration is typically used as a high-speed access service or uplink to another router. A common use is to provision IP over ATM circuits over DSL to connect businesses to the Internet—a B-RAS alternative to circuit aggregation. All provisioning can be through the RADIUS server to minimize any configuration of the router.

When IP packets are received over ATM circuits, the IP interfaces are dynamically constructed over the corresponding ATM 1483 interfaces from the configuration data received from the RADIUS server, a profile, or both.

Figure 31 shows the protocol layers that represent the IPoA interface columns, and the layers within the interface columns that are static and dynamic.

Figure 31: Dynamic IPoA over Static ATM 1483 Interface Columns

When you configure dynamic IPoA interfaces, you must assign a profile. Optionally, you can also assign a subscriber identification.

Configuring an IPoA Dynamic Interface

To configure dynamic IPoA interfaces:

1. Configure a physical interface.

For ATM interfaces on ERX-7xx models, ERX-14xx models, and the ERX-310 router, use the slot/port format; for example:

host1(config)#interface atm 5/0 

2. Configure an ATM subinterface.

host1(config-if)#interface atm 5/0.1

3. Configure a PVC by specifying the VCD, the VPI, the VCI, and the encapsulation type.
   

   NOTE: If you want the router to autodetect the encapsulation type, use the aal5autoconfig option.

   
   

host1(config-subif)#atm pvc 10 100 22 aal5snap

host1(config-subif)#atm pvc 10 100 22 aal5autoconfig

4. Assign a profile.

host1(config-subif)#profile ip foo

5. (Optional) Assign subscriber identification.

host1(config-subif)#subscriber ip user charlie domain myispname password lucy

6. Do either of the following:

• Configure the subinterface to recognize the dynamic IP encapsulation type using the default lockout time range, 1-300 seconds.

host1(config-subif)#auto-configure ip

• Configure the subinterface to recognize the dynamic IP encapsulation type using a nondefault lockout time range. For example, the following command configures 3600 seconds (1 hour) as the minimum lockout time and 7200 seconds (2 hours) as the maximum lockout time.

host1(config-subif)#auto-configure ip lockout-time 3600 7200

7. (Optional) Verify your configuration.

host1#show atm subinterface atm 5/0.1

atm pvc

• Use to configure a PVC on an ATM interface. Specify one of the following encapsulation types:

• aal5autoconfig—Enables autodetection of the 1483 encapsulation (LLC/SNAP or VC multiplexed).
• aal5snap—Specifies an LLC encapsulated circuit; LLC/SNAP header precedes the protocol datagram.
• aal5mux ip—Specifies a VC multiplexed circuit. This option is used for IP only.

• Example

host1(config-subif)#atm pvc 6 0 11 aal5autoconfig

• Use the no version to remove the specified PVC.

auto-configure

• Use to configure an ATM subinterface to support a dynamic interface. Specifies the type(s) of dynamic encapsulation that are accepted/detected by the ATM 1483 subinterface.
• This command creates the layers above ATM 1483 dynamically.
• Select the dynamic next upper-interface type from these options: bridgedEthernet, ip, ppp, or pppoe.
• You can issue this command repetitively to support multiple dynamic interface types.
• Encapsulation type lockout is performed on a per encapsulation type basis for each ATM 1483 subinterface. An encapsulation type not configured for autodetection with the auto-configure command is automatically locked out. The lockout, which is temporary, prevents the detection, acceptance, and creation of the encapsulation type until the lockout time expires.
• Use the none keyword to disable the lockout feature for the encapsulation type.
  

  NOTE: Disabling lockout can result in undesirable loading time; we recommend that you not disable lockout for general use. At a minimum, use the default lockout time.

  
  
• Use the lockout-time keyword to set the minimum and maximum lockout time period. This lockout range is 1-86400 seconds (24 hours). The default range is 1-300 seconds (5 minutes). The lockout time value is defined to be:

• (minimum lockout time) * (2 ^ n-1)
• n represents the number of consecutive lockout events. n is incremented when the time between lockout events is within 15 minutes or the maximum lockout time, whichever is greater. Otherwise, n reverts to 1 when the time between lockout events is greater than either 15 minutes or the maximum lockout time.
• The lockout time never exceeds the maximum configured lockout time. For example, for a configured lockout time of 20-120 seconds, the increasing lockout time sequence is 20 seconds, 40 seconds, 80 seconds, and finally, 120 seconds.

• A short-cycle event is a dynamic interface that is created and torn down within 60 seconds. The time between short-cycle events is tracked to determine whether the lockout time should increase for a subsequent short-cycle event.
  

  NOTE: When the calculated lockout time is equal to or exceeds the maximum lockout time, the router uses the maximum lockout time until the time to the next event exceeds the greater of 15 minutes or the maximum lockout time. At that point, the lockout time reverts to the minimum lockout time.

  
  
• The minimum lockout time value cannot exceed the maximum lockout time value. When the minimum and maximum values are equal, the encapsulation type lockout time becomes fixed.
• Example 1—Enables autodetection for the bridged Ethernet encapsulation type using the default lockout time range, 1-300 seconds

host1(config-subif)#auto-configure bridgedEthernet

• Example 2—Enables autodetection for the bridged Ethernet encapsulation type using a nondefault lockout time range, 3600-21600 seconds (1-6 hours)

host1(config-subif)#auto-configure bridgedEthernet lockout-time 3600 21600

• Example 3—Disables encapsulation type lockout for the IP encapsulation type

host1(config-subif)#auto-configure ip lockout-time none

• Example 4—Either command reenables encapsulation type lockout for the IP encapsulation type using the default lockout time range

host1(config-subif)#auto-configure ip 

host1(config-subif)#no auto-configure ip lockout-time

• Example 5—Permanently locks out the PPP encapsulation type until the auto-configure ppp command is issued

host1(config-subif)#no auto-configure ppp

• Use the no version to terminate detection of the specified encapsulation type or, if the lockout-time keyword is specified, to restore the lockout time range to its default values, 1-300 seconds.

interface atm

• Use to select an ATM interface or ATM 1483 subinterface.
• Use the slot/port[.subinterface ] format to select ATM interface and subinterfaces on ERX-7xx models, ERX-14xx models, and ERX-310 routers.
• For more information, see Creating a Basic Configuration in Chapter 1, Configuring ATM.
• Example

host1(config)#interface atm 5/0.1

• Use the no version to remove the interface or subinterface.

profile

• Use to assign a profile.
• You must specify the encapsulation type to which the profile applies: bridgedEthernet, ip, ppp, pppoe, or any.
• Specify a profile name with up to 80 characters.
• Example

host1(config-subif)#profile ppp foo

• Use the no version to remove a profile assignment.

subscriber

• Use to configure a local subscriber on the E-series router to support authentication and configuration from RADIUS for a dynamic IPoA or bridged Ethernet interface.
• When you configure a subscriber, you must specify the following:

• interfaceType—Type of dynamic interface, bridgedEthernet or ip
• userNameUsage—How the dynamic interface uses the username for authentication purposes

• user—Use the name as specified.
• user-prefix—Use the name as a prefix to the interface physical location. The router automatically postpends the physical location of the user to the username string. The username format is user.slot.port.vpi.vci. The resulting username string is then used to authenticate with the RADIUS server.

• userName—RADIUS username
• domainName—Domain name

• You may optionally supply password information:

• passwordUsage—How the dynamic interface uses the password for authentication purposes

• password—Use the password as specified.
• password-prefix—Use the password as a prefix to the interface physical location. The router automatically postpends the physical location of the user to the password string. The password format is password.slot.port.vpi.vci. The resulting password string is then used to authenticate with the RADIUS server.

• password—The RADIUS password

• Example

host1(config-subif)#subscriber ip user-prefix charlie domain myisp 
password-prefix lucy

• Use the no version to remove the subscriber.