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IPv6 Address Prefix Text Representation
IPv6 VPN over MPLS
IPv6 VPN over MPLS (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 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
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:
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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.
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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.
IPv6 Addressing
IPv6 addresses are 128-bit identifiers for interfaces and sets of interfaces. Cisco ANA supports the following IPv6 address types:
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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:
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Note
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 8-1 lists examples.
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 8-2 lists examples.
Table 8-2 IPv6 and IPv4 Address Notation
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:CD30:0000:0000:0000:0000/6012AB::CD30:0:0:0:0/6012AB:0:0:CD30::/60When 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/60Cisco 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::/60If a prefix length is not explicitly specified, it is calculated as the number of furthest left significant bits in the subnet address.
IPv6 and Cisco ANA
The Cisco ANA IPv6 implementation supports:
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