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.

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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.