ADSL Support in IPv6

Asymmetric Digital Subscriber Line (ADSL) support in IPv6 provides the extensions that make large-scale access possible for IPv6 environments, including IPv6 RADIUS attributes, stateless address configuration on PPP links, per-user static routes, and ACLs.

Restrictions for ADSL Support in IPv6

ADSL and dial deployment are available for interfaces with PPP encapsulation enabled, including PPP over ATM (PPPoA), PPP over Ethernet (PPPoE), PPP over async, and PPP over ISDN.

ADSL Support in IPv6

Address Assignment for IPv6

A Cisco router configured with IPv6 will advertise its IPv6 prefixes on one or more interfaces, allowing IPv6 clients to automatically configure their addresses. In IPv6, address assignment is performed at the network layer, in contrast to IPv4 where a number of functions are handled in the PPP layer. The only function handled in IPv6 control protocol is the negotiation of a unique interface identifier. Everything else, including Domain Name Server (DNS) server discovery, is done within the IPv6 protocol itself.

Contrary to IPv4 address assignment, an IPv6 user will be assigned a prefix, not a single address. Typically, the ISP assigns a 64- or 48-bit prefix.

In IPv6, ISPs assign long-lived prefixes to users, which has some impact on the routing system. In typical IPv4 environments, each network access server (NAS) has a pool of 24-bit addresses and users get addresses from this pool when dialing in. If a user dials another point of presence (POP) or is connected to another NAS at the same POP, a different IPv4 address is assigned.

Addresses for IPv6 are assigned using two methods:

Stateless Address Autoconfiguration

Assigning addresses using the stateless address autoconfiguration method can be used only to assign 64-bit prefixes. Each user is assigned a 64-bit prefix, which is advertised to the user in a router advertisement (RA). All addresses are automatically configured based on the assigned prefix.

A typical scenario is to assign a separate 64-bit prefix per user; however, users can also be assigned a prefix from a shared pool of addresses. Using the shared pool limits addresses to only one address per user.

This method works best for the cases where the customer provider edge (CPE) router is a single PC or is limited to only one subnet. If the user has multiple subnets, Layer 2 (L2) bridging, multilink subnets or proxy RA can be used. The prefix advertised in the RA can come from an authorization, authentication, and accounting (AAA) server, which also provides the prefix attribute, can be manually configured, or can be allocated from a prefix pool.

The Framed-Interface-Id AAA attribute influences the choice of interface identifier for peers and, in combination with the prefix, the complete IPv6 address can be determined.

How to Configure ADSL Support in IPv6

Configuring the NAS

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. hostname name
  4. aaa new-model
  5. aaa authentication ppp {default | list-name } method1 [method2 ...]
  6. aaa authorization configuration default {radius | tacacs+
  7. show ipv6 route [ipv6-address | ipv6-prefix / prefix-length | protocol | interface-type interface-number
  8. virtual-profile virtual-template number
  9. interface serial controller-number : timeslot
  10. encapsulation encapsulation-type
  11. exit
  12. dialer-group group-number
  13. ppp authentication protocol1 [protocol2 ...] [if-needed ] [list-name | default ] [callin ] [one-time ] [optional ]
  14. interface virtual-template number
  15. ipv6 enable
  16. dialer-list dialer-group protocol protocol-name {permit | deny | list access-list-number | access-group }
  17. radius-server host {hostname | ip-address } [test username user-name ] [auth-port port-number ] [ignore-auth-port ] [acct-port port-number ] [ignore-acct-port ] [timeout seconds ] [retransmit retries ] [key string ] [alias {hostname | ip-address }] [idle-time seconds

DETAILED STEPS

  Command or Action Purpose

Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

hostname name

Example:


Router(config)# hostname cust1-53a

Specifies the hostname for the network server.

Step 4

aaa new-model

Example:


Router(config)# aaa new-model

Enables the AAA server.

Step 5

aaa authentication ppp {default | list-name } method1 [method2 ...]

Example:


Router(config)# aaa authentication ppp default if-needed group radius

Specifies one or more AAA authentication methods for use on serial interfaces that are running PPP.

Step 6

aaa authorization configuration default {radius | tacacs+

Example:


Router(config)# aaa authorization configuration default radius

Downloads configuration information from the AAA server.

Step 7

show ipv6 route [ipv6-address | ipv6-prefix / prefix-length | protocol | interface-type interface-number

Example:


Router(config)# show ipv6 route

Shows the routes installed by the previous commands.

Step 8

virtual-profile virtual-template number

Example:


Router(config)# virtual-profile virtual-template 1

Enables virtual profiles by virtual interface template.

Step 9

interface serial controller-number : timeslot

Example:


Router(config)# interface serial 0: 15

Specifies a serial interface created on a channelized E1 or channelized T1 controller (for ISDN PRI, channel-associated signaling, or robbed-bit signaling).

This command also puts the router into interface configuration mode.

Step 10

encapsulation encapsulation-type

Example:


Router(config-if)# encapsulation ppp

Sets the encapsulation method used by the interface.

Step 11

exit

Example:


Router(config-if)# exit

Returns to global configuration mode.

Step 12

dialer-group group-number

Example:


Router(config)# dialer-group 1

Controls access by configuring an interface to belong to a specific dialing group.

Step 13

ppp authentication protocol1 [protocol2 ...] [if-needed ] [list-name | default ] [callin ] [one-time ] [optional ]

Example:


Router(config)# ppp authentication chap

Enables Challenge Handshake Authentication Protocol (CHAP) or Password Authentication Protocol (PAP) or both and specifies the order in which CHAP and PAP authentication are selected on the interface.

Step 14

interface virtual-template number

Example:


Router(config)# interface virtual-template 1

Creates a virtual template interface that can be configured and applied dynamically in creating virtual access interfaces.

Step 15

ipv6 enable

Example:


Router(config)# ipv6 enable

Enables IPv6 processing on an interface that has not been configured with an explicit IPv6 address.

Step 16

dialer-list dialer-group protocol protocol-name {permit | deny | list access-list-number | access-group }

Example:


Router(config)# dialer-list 1 protocol ipv6 permit

Defines a dial-on-demand routing (DDR) dialer list for dialing by protocol or by a combination of a protocol and a previously defined access list.

Step 17

radius-server host {hostname | ip-address } [test username user-name ] [auth-port port-number ] [ignore-auth-port ] [acct-port port-number ] [ignore-acct-port ] [timeout seconds ] [retransmit retries ] [key string ] [alias {hostname | ip-address }] [idle-time seconds

Example:


Router(config)# radius-server host 172.17.250.8 auth-port 1812 acct-port 1813 key testing123

Specifies a RADIUS server host.

Configuring the Remote CE Router

SUMMARY STEPS

  1. enable
  2. configure terminal
  3. hostname name
  4. interface bri number . subinterface-number [multipoint | point-to-point ]
  5. encapsulation encapsulation-type
  6. ipv6 address autoconfig [default
  7. isdn switch-type switch-type
  8. ppp authentication {protocol1 [protocol2 ...]} [if-needed ] [list-name | default ] [callin ] [one-time ]
  9. ppp multilink [bap | required ]
  10. exit
  11. dialer-list dialer-group protocol protocol-name {permit | deny | list access-list-number | access-group }
  12. ipv6 route ipv6-prefix / prefix-length {ipv6-address | interface-type interface-number ipv6-address ]} [administrative-distance ] [administrative-multicast-distance | unicast | multicast ] [tag tag

DETAILED STEPS

  Command or Action Purpose

Step 1

enable

Example:


Router> enable

Enables privileged EXEC mode.

  • Enter your password if prompted.

Step 2

configure terminal

Example:


Router# configure terminal

Enters global configuration mode.

Step 3

hostname name

Example:


Router(config)# hostname cust1-36a

Specifies the hostname for the network server.

Step 4

interface bri number . subinterface-number [multipoint | point-to-point ]

Example:


Router(config)# interface bri 1.0

Configures a BRI interface.

Step 5

encapsulation encapsulation-type

Example:


Router(config-if)# encapsulation ppp

Sets the encapsulation method used by the interface.

Step 6

ipv6 address autoconfig [default

Example:


Router(config-if)# ipv6 address autoconfig

Indicates that the IPv6 address will be generated automatically.

Step 7

isdn switch-type switch-type

Example:


Router(config-if)# isdn switch-type basic-net3

Specifies the central office switch type on the ISDN interface.

Step 8

ppp authentication {protocol1 [protocol2 ...]} [if-needed ] [list-name | default ] [callin ] [one-time ]

Example:


Router(config-if)# ppp authentication chap

Enables Challenge Handshake Authentication Protocol (CHAP) or Password Authentication Protocol (PAP) or both and specifies the order in which CHAP and PAP authentication are selected on the interface.

Step 9

ppp multilink [bap | required ]

Example:


Router(config-if)# ppp multilink

Enables Multilink PPP (MLP) on an interface and, optionally, enables Bandwidth Allocation Control Protocol (BACP) and Bandwidth Allocation Protocol (BAP) for dynamic bandwidth allocation.

Step 10

exit

Example:


Router(config-if)# exit

Exits interface configuration mode and returns to global configuration mode.

Step 11

dialer-list dialer-group protocol protocol-name {permit | deny | list access-list-number | access-group }

Example:


Router(config)# dialer-list 1 protocol ipv6 permit

Defines a dial-on-demand routing (DDR) dialer list for dialing by protocol or by a combination of a protocol and a previously defined access list.

Step 12

ipv6 route ipv6-prefix / prefix-length {ipv6-address | interface-type interface-number ipv6-address ]} [administrative-distance ] [administrative-multicast-distance | unicast | multicast ] [tag tag

Example:


Router(config)# ipv6 route 2001:DB8::1/128 BRI1/0

Establishes static IPv6 routes.

  • Use one command for each route.

Configuration Examples for ADSL Support in IPv6

Example: NAS Configuration

This configuration for the ISP NAS shows the configuration that supports access from the remote CE router. 

hostname cust1-53a
  aaa new-model
  aaa authentication ppp default if-needed group radius
  aaa authorization network default group radius 
  virtual-profile virtual-template 1
  interface Serial0:15
   encapsulation ppp
   dialer-group 1
   ppp authentication chap
  !
  interface Virtual-Template1
   ipv6 enable
  !
  dialer-list 1 protocol ipv6 permit
  radius-server host 172.17.250.8 auth-port 1812 acct-port 1813 key testing123

Example: Remote CE Router Configuration

This configuration for the remote customer edge router shows PPP encapsulation and IPv6 routes defined. 

hostname cust-36a
  interface BRI1/0
   encapsulation ppp
   ipv6 enable
   isdn switch-type basic-net3
   ppp authentication chap optional
   ppp multilink
  !
  dialer-list 1 protocol ipv6 permit
  ipv6 route 2001:DB8::1/128 BRI1/0
  ipv6 route ::/0 2001:DB8::1

Additional References

Related Documents

Related Topic

Document Title

Cisco IOS IPv6 features

Cisco IOS IPv6 Feature Mapping

Standards and RFCs

Standard/RFC

Title

RFCs for IPv6

IPv6 RFCs

MIBs

MIB

MIBs Link

To locate and download MIBs for selected platforms, Cisco IOS releases, and feature sets, use Cisco MIB Locator found at the following URL:

http://www.cisco.com/go/mibs

Technical Assistance

Description

Link

The Cisco Support and Documentation website provides online resources to download documentation, software, and tools. Use these resources to install and configure the software and to troubleshoot and resolve technical issues with Cisco products and technologies. Access to most tools on the Cisco Support and Documentation website requires a Cisco.com user ID and password.

http://www.cisco.com/cisco/web/support/index.html

Feature Information for ADSL Support in IPv6

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 ADSL Support in IPv6

Feature Name

Releases

Feature Information

IPv6 ADSL and Dial Deployment Support

12.2(13)T

ADSL and dial deployment provide the extensions that make large-scale access possible for IPv6 environments, including IPv6 RADIUS attributes, stateless address configuration on PPP links, per-user static routes, and ACLs.

The following commands were introduced or modified: aaa authentication ppp , aaa authorization multicast default , aaa new-model , dialer-group , dialer-list , encapsulation , hostname , ipv6 address autoconfig , ipv6 route , isdn switch-type , ppp authentication , ppp multilink , radius-server host , show ipv6 route , virtual-profile virtual-template .

IPv6 Access Services: PPPoA

12.2(13)T

12.3

12.3(2)T

12.4

12.4(2)T

ADSL and dial deployment is available for interfaces with PPP encapsulation enabled, including PPPoA.

IPv6 Access Services: PPPoE

12.2(13)T

12.3

12.3(2)T

12.4

12.4(2)T

ADSL and dial deployment is available for interfaces with PPP encapsulation enabled, including PPPoE.