The NPTv6 feature supports IPv6-to-IPv6 Network Prefix Translation (NPTv6) which enables a router to translate an IPv6 packet
header to IPv6 packet header and vice versa. The IPv6-to-IPv6 Network Prefix Translation (NPTv6) provides a mechanism to translate
an inside IPv6 source address prefix to outside IPv6 source address prefix in IPv6 packet header and vice-versa. A router
that implements an NPTv6 prefix translation function is referred to as an NPTv6 Translator.
Finding Feature Information
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information about the features documented in this module, and to see a list of the
releases in which each feature is supported, see the feature information table.
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Information About NPTv6 support
The IPv6-to-IPv6
Network Prefix Translation (NPTv6) serves as a useful mechanism for
implementing address independence in an IPv6 environment. A major benefit
associated with NPTv6 is the fact that it avoids the requirement for an NPTv6
Translator to rewrite the transport layer headers which reduces the load on
network devices. NPTv6 also does not interfere with encryption of the full IP
payload.
The NPTv6 support allows for greater reliability as it provides support for load balancing and achieves the translation without
breaking the end-to-end reachability at the network layer.
The following sections provide details about NPTv6 support:
Benefits of Using NPTv6 support
The NPTv6 support allows you to redirect or forward packets from one network to another in an IPV6 environment. The NPTv6
support on is an algorithmic translation function which provides a 1:1 relationship between the addresses within the inside
and outside network. When NTPv6 is used, you can interconnect different networks and support multihoming, load balancing,
peer-to-peer networking. The NPTv6 does not create any state in the date plane and hence can operate using minimal memory
and also supports high availability by default.
The NPTv6 supports prefix longer than 64 bits and also supports static IPv6 host to host translations. You can configure IPv4
and IPv6 translations on the same interface using NPTv6 support and scaling is supported. The NPTv6 feature also supports
Packet tracing and conditional debugging.
Restrictions for NPTv6 support
Multicast is not
supported.
Firewall is not
supported.
High Speed
Logging (HSL) and syslog is not supported..
IPv6 Prefix
Format
The NPTv6 support uses IPv6 prefix format for translation. The first 48 bits of the Ipv6 address represents the IPv6 prefix.
The NPTv6 Translator is used to translate the address prefixes. The translation function first ensures that the internal and
external prefixes are of the same length and if not, extends the shorter of the two with zeroes.
NPTv6 Translation
Inside to Outside Network
In NPTv6 a datagram
is allowed to pass through the NPTv6 Translator from an internal to an external
network. When the pass is from an internal to external network, the internal
prefix is overwritten with the external prefix and the header checksum is
generated.
NPTv6 Translation Outside to Inside Network
In NPTv6, when a datagram passes from an external network to an internal
network through an NPTv6 Translator, the external prefix is overwritten with
the internal prefix and the header checksum is generated.
Configuring NPTv6
You can configure
the inside and outside prefix for NPTv6 translation.
Use the
show nat66
statistics command to verify the NAT66 interface and global configuration:
Device# show nat66 statistics
NAT66 Statistics
Global Stats:
Packets translated (In -> Out)
: 7
Packets translated (Out -> In)
: 7
Use the
show platform
hardware qfp active feature nat66 datapath basecfg command to verify the
global stateless NPTv6 prefix in the data plane along with other base
configuration information:
Device# show platform hardware qfp active feature nat66 datapath basecfg
nat66 cfg_flags 0x00000001, dbg_flags 0x00000000
nat66_prefix_hash_table_entries 2048, nat66_prefix_hash_table 0x89628400
prefix hasht 0x89628400 max 2048 chunk 0x8c392bb0 hash_salt 719885386
Use the
show platform
hardware qfp active feature nat66 datapath prefix command to verify the
passed interfaces stateless NPTv6 prefix configuration:
You must make sure that the inside and outside interfaces are
configured.
Use the following debug commands if you have any configuration issues:
debug platform hardware qfp active feature nat66
datapath detailed- Provides detailed debugging information about
the data plane layer.
debug platform hardware qfp active feature nat66
datapath all- Displays debugging information about the data plane
layer.
debug platform condtion feature nat66 datapath submode
detailed- Provides data plane layer debugging information using
buginf_cond. ACL filter can be supplied via the debug condition infrastructure.
Use Cases for NPTv6 support
Single Inside
and Outside Network
You can use an
NPTv6 Translator to interconnect two network links, one which is an internal
network linked to a leaf network which is within a single administrative domain
and the other which is external network with connectivity to a global network
like the Internet. All hosts on the internal network use addresses from a
single prefix which is routed locally. The addresses will be translated to and
from the addresses in a globally routable prefix when the IP datagrams transit
the NPTv6 Translator. The lengths of these two prefixes will be functionally
the same and if the prefix lengths are different, the longer of the two
prefixes limits the ability to use subnets in the shorter prefix.
The figure below
illustrates NPTv6 deployment having a single inside and outside network.
Figure 1. NPTv6 using
Single Inside and Outside Network
Redundancy and
Load Sharing
When more than
one NPTv6 Translator is attached to a network, the NPTv6 Translators are
configured with the same internal and external prefixes. Since the translation
is algorithmic, even though there are multiple translators, they map only one
external address to the internal address.
The figure below
illustrates NPTv6 deployment in redundancy and load-sharing network.
Figure 2. NPTv6 in
Redundancy and Loadsharing Network
Multihoming
In a multihomed
network the NPTv6 Translators are attached to an internal network, but are
connected to different external networks. The NPTv6 Translators are configured
with the same internal prefix but different external prefixes. Since there are
multiple translations, the NPTv6 Translator maps multiple external addresses to
the common internal address.
The figure below
illustrates NPTv6 deployment in multihoming network.
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