Manual Chapter : Using DS-Lite with CGNAT

Applies To:

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BIG-IP LTM

  • 15.0.1, 15.0.0
Manual Chapter

Using DS-Lite with CGNAT

Overview: DS-Lite Configuration on BIG-IP systems

As IPv4 addresses are becoming depleted, service providers (DSL, cable, and mobile) face the challenge of supplying IP addresses to new customers. Providing IPv6 addresses alone is often not workable, because most of the public Internet still uses only IPv4, and many customer systems do not yet fully support IPv6. The Dual-Stack Lite (DS-Lite) tunneling technology is one solution to this problem. DS-Lite gives service providers the means to migrate to an IPv6 access network without changing end user devices or software.

What is DS-Lite?

DS-Lite
is an IPv4-to-IPv6 transition technology, described in RFC 6333, that uses tunneling and network address translation (NAT) to send IPv4 packets over an IPv6 network. This technology makes it possible, for example, for a service provider with an IPv6 backbone to properly route traffic while overlapping IPv4 networks.

How does DS-Lite work?

The customer-premises equipment (CPE), known as the B4 (Basic Bridging BroadBand) device, encapsulates the IPv4 packets inside IPv6 packets, and sends them to the AFTR (Address Family Transition Router) device. The AFTR device includes carrier-grade NAT (CGNAT), which has a global IPv4 address space. The AFTR device decapsulates the IPv4 traffic and performs address translation, as it sends the traffic to the external IPv4 network.

How does F5 implement DS-Lite?

On the BIG-IP® system, a DS-Lite tunnel is a variation of IPIP tunnels that uses augmented flow lookups to route traffic.
Augmented flow lookups
include the IPv6 address of the tunnel to identify the accurate source of packets that might have the same IPv4 address. When the BIG-IP device receives an IPv6 encapsulated packet, the system terminates the tunnel, decapsulates the packet, and marks it for DS-Lite. When the system re-injects the packet into the IP stack, it performs an augmented flow lookup to properly route the response.

Illustration of a DS-Lite deployment

In this example, a service provider transports encapsulated IPv4 traffic over its IPv6 network.
Example of a DS-Lite configuration
Example of a DS-Lite configuration

About CGNAT hairpinning

An optional feature on the BIG-IP system,
hairpinning
routes traffic from one subscriber's client to an external address of another subscriber's server, where both client and server are located in the same subnet. To each subscriber, it appears that the other subscriber's address is on an external host and on a different subnet. The BIG-IP system can recognize this situation and send, or hairpin, the message back to the origin subnet so that the message can reach its destination.
In order for hairpinning to function properly, the subscriber VLAN must be configured as an egress interface on the LSN pool. If the subscriber VLAN is not configured as an egress interface on the LSN pool, hairpinning fails.
At present hairpinning works with all BIG-IP CGNAT scenarios except NAT64.

Creating a DS-Lite tunnel on the BIG-IP device as an AFTR device

Before you configure the tunnel, ensure that the BIG-IP device you are configuring has an IPv6 address.
You can create a DS-Lite (wildcard) tunnel for terminating IPv4-in-IPv6 tunnels to remote B4 devices, and recycling the IPv4 address space.
  1. On the Main tab, click
    Network
    Tunnels
    Tunnel List
    Create
    or
    Carrier Grade NAT
    Tunnels
    Create
    .
    The New Tunnel screen opens.
  2. In the
    Name
    field, type a unique name for the tunnel.
  3. From the
    Profile
    list, select
    dslite
    .
  4. In the
    Local Address
    field, type the IPv6 address of the local BIG-IP device.
  5. For the
    Remote Address
    setting, retain the default selection,
    Any
    , which indicates a wildcard IP address.
  6. Click
    Finished
    .
You have now created a DS-Lite tunnel that functions as an AFTR (Address Family Translation Router) device.

Assigning a self IP address to an AFTR device

Ensure that you have created a DS-Lite tunnel before you start this task.
Self IP addresses can enable the BIG-IP system, and other devices on the network, to route application traffic through the associated tunnel.
  1. On the Main tab, click
    Network
    Self IPs
    .
  2. Click
    Create
    .
    The New Self IP screen opens.
  3. In the
    Name
    field, type a unique name for the self IP address.
  4. In the
    IP Address
    field, type an IP address.
    This IP address is the IPv4 gateway that the B4 devices use to reach the Internet. F5 recommends using the IP address space that the IANA has specifically allocated for an AFTR device, for example,
    192.0.0.1
    .
  5. In the
    Netmask
    field, type the network mask for the specified IP address.
    For example, you can type
    255.255.255.0
    .
  6. From the
    VLAN/Tunnel
    list, select the tunnel with which to associate this self IP address.
  7. Click
    Finished
    .

Configuring CGNAT for DS-Lite

Before starting this task, ensure that CGNAT is licensed and the feature module enabled on the BIG-IP system, and you have created at least one LSN pool.
When you are configuring DS-Lite, you must set up a forwarding virtual server to provide the Large Scale NAT (LSN), which is specified by the DS-Lite tunnel as an augmented flow lookup.
  1. On the Main tab, click
    Carrier Grade NAT
    Virtual Servers
    .
    The Virtual Server List screen opens.
  2. Click
    Create
    .
    The New Virtual Server screen opens.
  3. In the
    Name
    field, type a unique name for the virtual server.
  4. From the
    Type
    list, select
    Performance (Layer 4)
    .
  5. In the
    Destination Address
    field, type
    0.0.0.0/0
    to translate all IPv4 traffic.
  6. In the
    Service Port
    field, type
    *
    or select
    * All Ports
    from the list.
  7. From the
    Configuration
    list, select
    Advanced
    .
  8. From the
    Protocol
    list, select
    * All Protocols
    .
  9. From the
    LSN Pool
    list, select an LSN pool.
  10. Click
    Finished
    .
This virtual server now intercepts traffic leaving the DS-Lite tunnel, provides the LSN address translation, and forwards the traffic to the IPv4 gateway.

Verifying traffic statistics for a DS-Lite tunnel

After you configure DS-Lite on a BIG-IP system, you can check the statistics for the tunnel to verify that traffic is passing through it.
  1. Log on to the BIG-IP command-line interface.
  2. At the command prompt, type
    tmsh show sys connection all-properties
    .
    The result should show tunnel with
    any
    as the remote endpoint (on the first line), and
    ipencap
    as the
    Protocol
    , as shown in the example.
    2001:db8::/32.any - 2001:db8::46.any - any6.any - any6.any --------------------------------------------------------- TMM 0 Type any Acceleration none Protocol ipencap Idle Time 1 Idle Timeout 300 Unit ID 1 Lasthop /Common/wan 00:d0:01:b9:88:00 Virtual Path 2001:db8::46.any ClientSide ServerSide Client Addr 2001:db8::45.any any6.any Server Addr 2001:db8::46.any any6.any Bits In 171.6K 0 Bits Out 171.6K 0