Cisco Active Network Abstraction User Guide, 3.6.7
IPv6 VPN over MPLS
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IPv6 VPN over MPLS

Table Of Contents

IPv6 VPN over MPLS

6VPE Overview

Viewing IPv4 and IPv6 Information

Cisco ANA 6VPE Support Limitations

IPv6 Addressing

IPv6 Address Representation

IPv6 Address Prefix Text Representation

Provisioning Route Targets

Enabling IPv6 VRFs

Adding Route Targets with IPv4 and IPv6 Address Families

Removing Route Targets with IPv4 and IPv6 Address Families


IPv6 VPN over MPLS


IPv6 VPN over MPLS, also known as 6VPE, uses the existing MPLS IPv4 core infrastructure for IPv6 transport to enable IPv6 sites to communicate over an MPLS IPv4 core network using MPLS label switch paths (LSPs). 6VPE relies on MP-BGP extensions in the IPv4 network configuration on the PE router to exchange IPv6 reachability information. Edge routers are configured to be dual-stacks running both IPv4 and IPv6, and use the IPv4 mapped IPv6 address for IPv6 prefix reachability exchange.

The following topics tell you how you can use Cisco ANA to view and manage 6PVE implementations. Topics include:

6VPE Overview

Viewing IPv4 and IPv6 Information

Cisco ANA 6VPE Support Limitations

IPv6 Addressing

Provisioning Route Targets

6VPE Overview

Figure 8-1 illustrates the 6VPE network architecture and control plane protocols when two IPv6 sites communicate through an MPLS IPv4 backbone.

Figure 8-1 6VPE Network Architecture

Dual stack is a technique that lets IPv4 and IPv6 coexist on the same interfaces. Dual stack implementations depend on the network area:

Network Core—In the network core, IPv6 is carried in a VPN manner over a non IPv6-aware MPLS core. This allows IPv4 or IPv6 communities to communicate with each other over an IPv4 MPLS backbone without modifying the core infrastructure. By avoiding dual stacking on the core routers, resources can be dedicated to their primary function to avoid any complexity on the operational side. The transition and integration with respect to the current state of networks is also transparent.

Network Access—To support native IPv6, the access that connects to IPv4 and IPv6 domains must be IPv6-aware. Service PE elements can exchange routing information with end users; therefore, dual stacking is mandatory on the access layer.

When IPv6 is enabled on the subinterface that is participating in a VPN, it becomes an IPv6 VPN. The CE-PE link runs IPv6 or IPv4 natively. The addition of IPv6 on a PE router turns the PE into 6VPE, thereby enabling service providers to support an IPv6 over the MPLS network.

PE routers use VRF tables to maintain the segregated reachability and forwarding information of each IPv6 VPN. MP-BGP with its IPv6 extensions distributes the routes from 6VPE to other 6VPEs through a direct interior BGP (iBGP) session or through VPNv6 route reflectors. The next hop of the advertising PE router still retains the IPv4 address (normally it is a loopback interface), but with the addition of IPv6, a value of ::FFFF: is added to the IPv4 next hop.

The technique can be seen as automatic tunneling of the IPv6 packets through the IPv4 backbone. The MP-BGP relationships remain the same as they are for VPNv4 traffic, with an additional VPNv6 capability. Where both IPv4 and IPv6 are supported, the same set of MP-BGP peer relationships is used.

Viewing IPv4 and IPv6 Information

Cisco ANA transparently handles IPv4 and IPv6 addresses within the limitations described in the "Cisco ANA 6VPE Support Limitations" section. Cisco ANA NetworkVision displays IPv6 addresses when they are configured on PE and CE routers in the Cisco ANA NetworkVision IP interface table. The IP interface table appears in the following locations:

Port inventory view—IPv6 addresses appear under the Sub Interfaces tab in the interface table and interface properties popup window.

VRF inventory view—IPv6 addresses appear under the Sites tab in the interface table and interface properties popup window, and in the VRF IPV6 Routing Table tab. See Figure 7-5 on page 7-20.

Routing entity view—IPv6 addresses appear under the IP Interfaces tab in the table view when applicable, and the interface properties popup window.

MP-BGP—IP address family identifiers indicate the BGP peer address family: IPv4, IPv6, VPNv4 or VPNv6. For information, see Viewing MP-BGP Information, page 7-28.

The IP addresses that appear depend on whether the interface has only IPv4 addresses, only IPv6 addresses, or both IPv4 and IPv6 addresses, as shown in Table 8-1.


Note To display the properties window, right-click the IP address in the interface table and choose Properties.


Table 8-1 IP Addresses Displayed in the Interface Table and Properties Window

Addresses
Interface Table
Properties Window

IPv4 only

Primary IPv4 address

The primary IPv4 address and any secondary IPv4 addresses

IPv6 only

Lowest IPv6 address

All IPv6 addresses

IPv6 and IPv4

Primary IPv4 address

All IPv4 and IPv6 addresses


Figure 8-2 shows a port inventory view of a Cisco CRS-1 Carrier Routing System port with IPv4 and IPv6 addresses. In this example, one IPv4 address and multiple IPv6 addresses are provisioned on the interface.

The primary IPv4 address appears in the interface table and properties window. If secondary IPv4 addresses were provisioned on the interface, they would appear in the properties window.

IPv6 addresses provisioned on the interface appear in the properties window and Sub Interface tab.

Figure 8-2 Port with IPv4 and IPv6 Addresses

1

Port interface

4

Properties window

2

Port subinterface table

5

Primary IPv4 address

3

Primary IPv4 address

6

IPv6 addresses


Figure 8-3 shows a Cisco CRS-1 port with only IPv6 addresses provisioned. In this example, the lowest IPv6 address is shown in the subinterface table, and all IPv6 addresses are shown in the interface properties window.


Note For information on IPv6 addressing format, see IPv6 Addressing.


Figure 8-3 Port with IPv6 Addresses

1

Port interface

4

Properties window

2

Port subinterface table

5

All IPv6 addresses

3

Lowest IPv6 address

   

Cisco ANA 6VPE Support Limitations

Cisco ANA 6VPE support is limited to devices and software versions shown in Table 8-2.

Table 8-2 Supported 6VPE Devices

Device
Software Version
Notes

Cisco CRS-1 Carrier Routing System

Cisco IOS XR Release 3.7.1

6VPE device in an L3 VPN network.

Cisco CSR 12000 Series Aggregation Services Router

Cisco IOS XR Release 3.7.1

 
Supported Route Reflector Devices

Cisco 7206VXR

Cisco IOS Release 12.2(33)SRD1

 

In addition, Cisco ANA 6VPE support is characterized by the following:

Cisco ANA NetworkVision MPLS label switching, routing, and ARP tables do not display IPv6 addresses.

The Layer 1 topology between 6VPE and an IPv6 CE is discovered only when CDP is enabled.

Correlation flows between IPv6-only interfaces is not supported.


Note Interfaces or subinterfaces that do not have IP addresses are not discovered and therefore are not shown in Cisco ANA NetworkVision.


IPv6 Addressing

IPv6 addresses are 128-bit identifiers for interfaces and sets of interfaces. Cisco ANA supports the following IPv6 address types:

Unicast—Identifier for a single interface. A packet sent to a unicast address is delivered to the interface identified by that address.

Anycast—Identifier for a set of interfaces (typically belonging to different nodes). A packet sent to an anycast address is delivered to one of the interfaces identified by that address (the "nearest" one, according to how the routing protocol measures distance.

Multicast—Identifier for a set of interfaces (typically belonging to different nodes). A packet sent to a multicast address is delivered to all interfaces identified by that address.

Cisco ANA supports interfaces with multiple IPv6 addresses. The lowest IPv6 address is presented in the Cisco ANA tables; all addresses are shown in the detailed interface properties view. Cisco ANA does not model link-local unicast addresses because they are not used in the routing and forwarding tables.

The following sections provide additional IPv6 address format information:

IPv6 Address Representation

IPv6 Address Prefix Text Representation


Note For more IPv6 addressing information, see "RFC2460 - Internet Protocol, Version 6 (IPv6 Specification."


IPv6 Address Representation

IPv6 has three conventional text string representation forms. The preferred form is x:x:x:x:x:x:x:x, where x is the hexadecimal value of the eight 16-bit address pieces, for example:

FEDC:BA98:7654:3210:FEDC:BA98:7654:3210

1080:0:0:0:8:800:200C:417A

Because IPv6 addresses frequently contain long strings of zero bits, two colons (::) can be used to indicate multiple 16-bit groups of zeros. Table 8-3 shows examples.

Table 8-3 IPv6 Addresses with Compression 

Address Type
Noncompressed IPv6 Address
Compressed IPv6 Address

Unicast

1080:0:0:0:8:800:200C:417A

1080::8:800:200C:417A

Multicast

FF01:0:0:0:0:0:0

FF01::101

Loopback

0:0:0:0:0:0:0:1

::1

Unspecified

0:0:0:0:0:0:0:0

::


In mixed IPv4 and IPv6 address nodes, the format x:x:x:x:x:x:d.d.d.d is sometimes used where x represents the hexadecimal values of the six high-order 16-bit address pieces, and d represents the decimal value of the four low-order 8-bit pieces of the address (standard IPv4 representation). Table 8-4 shows examples.

Table 8-4 IPv6 and IPv4 Address Notation

Noncompressed IPv4 and IPv6 Address
Compressed IPv4 and IPv6 Address

0:0:0:0:0:0:13.1.68.3

::13.1.68.3

0:0:0:0:0:FFFF:129.144.52.38

::FFFF:129.144.52.38


Cisco ANA supports all the textual presentations of the IPv6 addresses. However, Cisco ANA NetworkVision displays compressed IPv6 addresses only.

IPv6 Address Prefix Text Representation

The text representation of IPv6 address prefixes is similar to the way IPv4 address prefixes are written in Classless Inter-Domain Routing (CIDR) notation. An IPv6 address prefix is represented by the notation:

ipv6-address/prefix-length

where:

ipv6-address is an IPv6 address in any of the notations listed previously.

prefix-length is a decimal value specifying how many of the furthest left contiguous bits of the address comprise the prefix.

The following are examples of IPv6 addresses with the 60-bit hexadecimal prefix,12AB00000000CD3:

12AB:0000:0000:CD30:0000:0000:0000:0000/60
12AB::CD30:0:0:0:0/60
12AB:0:0:CD30::/60

When writing both node address and a prefix of that node address (for example, the node's subnet prefix), you can combine the two. For example, the node address, 12AB:0:0:CD30:123:4567:89AB:CDEF, and its subnet number, 12AB:0:0:CD30::/60, can be abbreviated as:

12AB:0:0:CD30:123:4567:89AB:CDEF/60

Cisco ANA supports all the textual presentations of address prefixes. However, Cisco ANA NetworkVision displays both the IP address and the subnet prefix, for example:

12AB::CD30:123:4567:89AB:CDEF, 12AB:0:0:CD30::/60

If a prefix length is not explicitly specified, it is calculated as the number of furthest left significant bits in the subnet address.

Provisioning Route Targets

Cisco ANA allows you to create VRF route targets and assign IPv4 and IPv6 address families to them using one of the following methods:

In the Cisco NetworkVision device logical inventory, right-click a VRF and choose Add Route Target (see Figure 8-4).

Figure 8-4 Adding Route Target Using Cisco ANA NetworkVision

1

Logical inventory

3

Command option

2

VRFs

4

Add Route Target command


From Command builder, launch a route target with address family command (Figure 8-5).

Figure 8-5 Command Builder Route Target Commands


Note To assign address families to VPN communities, you must create the VRF with the vrf definition Cisco IOS command. Address families cannot be assigned to VRFs created with the ip vrf command.


After you launch the Cisco ANA NetworkVision or Command Builder command, the Add Route Target Import With Address Family or Add Route Target Export With Address Family dialog box appears (Figure 8-6). The dialog box contains an Input tab and a Results tab. The Input tab is where you enter the VPN community (either import or export), route target, and address family.

Figure 8-6 Add Route Target Export with Address Family Dialog Box

1

Input tab

5

Address Family field

2

Result tab

6

Preview button

3

VPN Community field

7

Execute button

4

Route Target field

   

Click Preview to view the command sequence in the Result tab (Figure 8-7).

Figure 8-7 Add Route Target Export with Address Family Preview

After you execute the command on the device, you view the commands that were executed on the device in the Result tab (Figure 8-8).

Figure 8-8 Execution Results for Add Route Target Export with Address Family

Use the following procedures to enable IPv6 VRFs and add or delete route targets with IPv4 and IPv6 address families:

Enabling IPv6 VRFs

Adding Route Targets with IPv4 and IPv6 Address Families

Removing Route Targets with IPv4 and IPv6 Address Families

Enabling IPv6 VRFs

To configure a VRF with an IPv6 address family, IPv6 VRF must be enabled on the device. You can do this in Cisco NetworkVision by completing the following steps:


Step 1 Display the Cisco NetworkVision inventory window.

Step 2 Right-click the ASR device where you want to enable the IPv6 VRF and choose Commands > VRF > Enable IPv6 VRF.

The Enable IPv6 VRF command window appears.

Step 3 Click Preview to preview the command.

A preview of the command that will be executed appears in the Preview tab.

Step 4 Click the Input tab, then click Execute.

The results are displayed in the Preview tab.

Step 5 Click Close.


Adding Route Targets with IPv4 and IPv6 Address Families

To add a route target with an IPv4 or IPv6 address family:


Step 1 In the Cisco ANA NetworkVision navigation pane, right-click the router containing the VRF to which you want to assign a route target and choose Inventory.

Step 2 In the device inventory view, expand the Logical Inventory tree until you reach the VRF to which you want to assign the route target with address family.

Step 3 Right-click the VRF and choose Commands > Add Route Target.

Step 4 In the Add Route Target dialog box Input tab, enter the following:

VPN Community—Choose the VPN community to which you want to add the route target address family, either Import or Export.

Route Target—Enter the route target in the format ASN:nn or IP-address:nn, where ASN is the associated system number and nn is the number assigned to the route target.

Address Family—Enter the address family:

IPv4—Assigns an IPv4 address family to the route target.

IPv6—Assigns an IPv6 address family to the route target.

Not_Set—Adds a route target without an address family.

Step 5 If you want to preview the route target, click Preview.

The Result tab displays the commands that will be executed on the device.

Step 6 Click Execute.

The Result tab displays the commands that were executed on the device.

Step 7 Click Close to close the window.


Removing Route Targets with IPv4 and IPv6 Address Families

To remove a route target with an IPv4 or IPv6 address family from a device:


Step 1 In the Cisco ANA NetworkVision navigation pane, right-click a router containing the VRF with the route target you want to remove and choose Inventory.

Step 2 In the device inventory view, expand the Logical Inventory tree until you find the VRF containing the route target you want to remove.

Step 3 Click the VRF.

The VRF properties appear in the Cisco ANA content area.

Step 4 Right-click an import route target or an export route target and choose Configuration > Remove route target (Figure 8-9).

Step 5 On the confirmation message box, click OK.

Figure 8-9 Deleting Route Targets

1

Logical inventory

4

Route target areas

2

VRFs

5

Remove route target menu item.

3

IP Address tab