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This document provides an overview of a proven solution for the distribution of globally routable IPv6 Addresses, leveraging Avaya VENA Fabric Connect. Fabric Connect is Avaya’s next-generation networking protocol; an enhanced implementation of the standardized Shortest Path Bridging (SPB) technology.
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This document provides an overview of a proven solution for the distribution of globally routable IPv6 Addresses, leveraging Avaya VENA Fabric Connect. Fabric Connect is Avaya’s next-generation networking protocol; an enhanced implementation of the standardized Shortest Path Bridging (SPB) technology.
The high level results of the work demonstrate that an enterprise can effectively use Fabric Connect to provide for the overlay of a routed IPv6 infrastructure that is incongruent to the existing IPv4 topology. Furthermore, with IPv4 default gateways resident on Layer 2 Virtual Service Networks, dual-stack end-stations can have full end-to-end hybrid connectivity without the use of Layer 3 transition methods such as 6to4, ISATAP, or Teredo. This results in a clean and simple implementation that allows for the use of allocated globally routable IPv6 addresses in a native fashion.
IPv6 in GeneralIPv6 is the next generation form of IP addressing. Replacing IPv4, it is intended
to greatly enhance address space as well as end-to-end transparency (which
was becoming more and more difficult to achieve) by increasing use of Network
Address Translation (NAT) in IPv4. NAT was created to provide for use of
‘private’ IPv4 addressing within an organization and then for a gateway
interface device to the public Internet; but even this technology could not
forestall the unavoidable end of available contiguous blocks of IPv4 addresses
which ran out earlier this year. Current efforts to recycle IPv4 addresses will
provide a short-lived reprieve however the supply of recycled addresses will be
quickly exhausted.
As a result, many enterprises that had IPv6 on the back-burner are now taking a
new look at this technology and its deployment requirements. Researching this
issues can be a daunting task because, beyond knowledge of IPv6 itself, one needs
to understand what’s required for IPv6 to co-exist in an IPv4 network environment.
Completely fork-lifting a company’s communications environment is not
practical and, even if an enterprise were willing to do this, issues regarding
contact with the outside world need to be addressed because the IPv6 suite is
not directly backwards compatible to IPv4. This lack of direct backwards
compatibility has generated efforts within the IETF to resolve this complication.
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Distribution of Globally Routable IPv6 over Avaya VENA Fabric Connect
Table of Contents
IPv6 in General ............................ 1
Test-Bed for IPv6 over
Fabric Connect ........................... 2
Ramifications on larger
IPv6 deployments ...................... 3
Summary ....................................... 4
Future Developments ............... 5
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A number of RFCs, drafts as well as deprecated drafts, covering a wide variety
of translation or transition methods have been written, each having its own set
of complications and security or resiliency issues that must be dealt with. At the
end of the day, most IT personnel walk away with a headache and wish for the
good old days of IPv4 only.
Since the introduction of IPv6, different schools of thought have arisen regarding
how to address co-existence between IPv4 and IPv6. Network and Port
Translation (NAT-PT), for example, once considered a possible solution, faded
into deprecation because the approach proved to be intractable for the most
part. Other methods have stayed and even become ‘default’; as an example, all
Microsoft OSs running IPv6 run 6to4, ISATAP and Teredo tunneling methods.
One school of thought has won out: dual-stack on the end-stations with
tunneling across the IPv4 network to tie IPv6 islands together. This method
works but, as mentioned earlier, even this method has complications and issues
that need to be dealt with.
If one looks at the evolution long enough however it becomes apparent that if
Layer 2 methods could provide the paths between IPv6 islands, things like 6to4,
ISATAP and Teredo are not required and having eliminated ISATAP and Teredo,
an enterprise is free to use formally allocated globally routable address space.
The only requirement for the dual-stack host is that it has clear default routes
for both IPv6 and IPv4. With typical VLAN based networks this design, while
feasible, does not scale and quickly becomes intractable due to the
complications of tagged trunk design within the network core. With Avaya’s
Fabric Connect capability, this scalable Layer 2 method is now available. The
following pages describe the test bed environment and ramifications of this
work on larger network infrastructures.
Test-Bed for IPv6 over Fabric ConnectThe figure on the following page depicts minimal requirements for a successful
hybrid IPv6 deployment over Fabric Connect. As the diagram shows, requirements
are fairly concise and simple; what is required is a Virtual Service Network (VSN)
that is associated with edge VLANs that host dual-stack end-stations.
Additionally, this VSN needs to attach to IPv6 and IPv4 default gateways enabled
by edge VLAN’s that interface to relevant devices.
Requirements are straight forward and
easy to understand. Illustrated in a simplified form, this topology has been
deployed in Avaya labs to demonstrate the proposed configuration.
For simplicity, in Avaya’s test-bed, a common VSN that would support the IPv6
deployment was implemented. More complicated IPv6 routed topologies can easily
be achieved by using Inter-VSN Routing with routers external to the Fabric Connect
cloud; illustrations of this are provided later in this document. In the lab, Avaya
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created VLAN ID 500 at three different key
points at the edge of the domain. A Virtual
Service Network was created within the
Fabric Connect domain (also using 500 as its
identifier) that ties the different VLANs
together. At one edge VLAN a Windows 7
end-station running dual-stack had the IPv4
Address of 10.40.99.2 and the IPv6 Address
of 3000::2 configured. For IPv4 the end-
stations default gateway was 10.40.99.1 and
for IPv6 the default gateway was 3000::1. The
IPv6 default gateway is also attached to
VLAN 500 and is able to provide directly
routable paths in and out of the VSN.
Additionally, the IPv4 default gateway is
attached and reachable.
The dual-stack end-station has end-to-end
hybrid connectivity to both IPv6 and IPv4
environments without the use of any Layer
3 transition method. The topology depicted
in figure 3 shows that from the perspective
of dual-stack end-stations there is complete
hybrid connectivity and available routed
paths to both IPv4 and IPv6 environments.
Connectivity out into INET2 to native IPv6
resources is enabled by the use of officially-
allocated global addressing.
Ramifications on larger IPv6 deploymentsA major drawback of Layer 3 transition
methods for IPv6 is that they bind the IPv6
topology to IPv4, which many find to be
undesirable. After all, they say, why
implement a new globally routed protocol
and then lock it down to an existing limited
legacy topology? A potential solution,
running IPv6 as “ships-in-the-night” with
IPv4, requires use of VLANs and tagged
trunks and, while shown to be feasible in
the previous test-bed (figure 2), this
approach suffers from complexity in larger
topologies and does not lend itself to scale.
Dual-Stack Host
IPv6 Gateway
IPv4 Layer 3VSN
Dual-Stack Layer 2 VSN
IPv6 Layer 3 VSN
IPv4 10.40.99.1
IPv6 3000::1 IPv6 3000::2 Gateway 3000::1
IPv4 10.40.99.2 Gateway 10.40.99.1
VLAN 500
VSN 500
Fabric Connect
Figure 2: Native IPv6 Dual-Stack over a Layer 2 VSN
Dual-Stack Hosts
IPv4 VSN
IPv6 VSN
IPv6 Network/Internet IPv6 Gateway
Dual-Stack Hosts
IPv4 Network/Internet IPv4 Host
Fabric Connect
Figure 3: Dual-stack End-Station perspective for default routed paths
Figure 2: Native IPv6 Dual-Stack over a Layer 2 VSN
Figure 3: Dual-stack End-Station perspective for default routed paths
Dual-Stack Hosts
IPv4 Host
IPv6 Host
IPv4 Virtual Service Network
IPv6 Virtual Service Network
IPv6 Network/Internet IPv6 Gateway
IPv4 Gateway
Fabric Connect
Figure 1: Required elements for a hybrid IPv6 deployment over Fabric Connect
Figure 1: Required elements for a hybrid IPv6 deployment over Fabric Connect
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Tractable on an enterprise scale, Fabric Connect vastly simplifies these issues
because the IPv6 deployment becomes an overlay Layer 3 environment that
rides on top of the underlying IS-IS protocol and therefore deploying it does not
require detailed configuration changes to the network core. This original “ships-
in-the-night” vision can now be realized in real world designs.
The following diagram shows a large network topology that interconnects two
Data Centers; the topology in blue shows
the IPv6 native deployment, with green
indicating the IPv4 legacy routed
environment. Note that while there are
common touch-points between the two
environments for legacy dual-stack IPv4
use, the two IP topologies are quite
independent of one another.
This is a very attractive trait as most
environments, when introducing the new
protocol, will want to take the opportunity
to redesign the network. In addition, it
allows for modification of one IP
environment without undue dependency on
the other.
SummaryThis document describes a simple topology design that can implement an IPv6
dual-stack host environment with full hybrid connectivity using Layer 2 VSNs
within a Fabric Connect domain. The use of Fabric Connect allows for true
enterprise scale deployments that avoid the complications of core tagged
trunks and routing. As such, the deployment of IPv6 becomes a very tractable
proposition with a number of notable benefits:
• Topological independence – there is no dependence on IPv4 topology; the two
IP environments are totally incongruent, providing great flexibility and scale.
• Services separation – the IPv6 deployment enjoys a separate logical transport that
is totally separated; resources are more clearly managed and SLAs can be achieved.
• Edge provisioning – this is a key feature of Avaya’s VENA framework; Fabric
Connect removes the need to configure the network core for various services
that it offers and, as a result, a huge amount of complexity and potential for
human error are effectively removed.
• Unmatched resiliency – the convergence times of the Fabric Connect mesh
are much faster than the Layer 3 routing timeouts and, as such, most failures
within the core will be transparent to both Layer 3 routing environments.
IPv6 & Dual-Stack Hosts
IPv6 Data Centers
IPv4 Host
IPv4 Gateway Fabric Connect
Figure 4: Totally Independent IP topologies
Figure 4: Totally Independent IP topologies
© 2013 Avaya Inc. All Rights Reserved.
All trademarks identified by ®, ™, or SM are registered marks, trademarks, and service marks, respectively, of Avaya Inc.
05/13 • LB4770-01
Further, if one routing environment were to have problems it would be isolated to that
environment and not affect the other. With Layer 3 transition methods such as 6to4, for
example, if the IPv4 topology has issues, it affects IPv6 connectivity, possibly even
prohibiting it. With Fabric Connect, all environments are separated, independent and
highly resilient.
Future DevelopmentsThe foundational protocol used Shortest Path Bridging is IS-IS and unlike OSPF – which
requires an update in order to support IPv6 – IS-IS is protocol agnostic. Research is
underway for Global Routing Table route injection of IPv6 directly into IS-IS, as well as
the ability to support Layer 3 VSNs with VRF for IPv6 to allow for integrated OSPFv3.
As this research and development effort becomes reality IPv6 routing will be absorbed
into the Fabric Connect cloud as just another protocol that is transported across. These
developments will enable a truly integrated approach to implementing IPv6 in an
extremely stable and scalable fashion. Avaya is fully committed to this future integrated
vision but, as this application note illustrates, very tractable implementations of IPv6
over Avaya VENA Fabric Connect can be realized today.
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About AvayaAvaya is a global provider of business collaboration and communications solutions,
providing unified communications, contact centers, networking and related services
to companies of all sizes around the world. For more information please visit
www.avaya.com.