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Mar 27th, 2009

Welcome to the Cisco Networking Professionals Ask the Expert conversation. This is an opportunity to learn how to deploy Internet Protocol version 6 in a SP environment to cope with the growing demand with Cisco expert Harold Ritter. Harold is a technical leader with the Cisco Advanced Services Central Engineering team. He is responsible for helping Cisco top-tier Service Provider customers to design, implement and troubleshoot routing protocols and multicast, for both IPv4 and IPv6, and MPLS solutions in their environment. He has been a network engineer for more than 14 years. Harold is a CCIE (#4168) for Routing & Switching and Service Provider.

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Mohamed Sobair Sun, 03/29/2009 - 08:02

Hello Harold,

Its a great opportunity talking to you.

I have 2 questions with regard to IPv6 deployment:

1- When does MPLS is going to natively support IPv6?

2- there are 4 ways to deploy IPv6 over MPLS:

a) 6PE.

b) 6 VPE.

c) AToM.

d) MPLS VPN Solution.

Which of those options do you usually recommend and why? As I know dual Stack PE has the advantage of running both IPv6 and IPv4 & the capability for migrating IPv4 Core Network to an IPv6. Does this the Only reason for having Dual Stack PEs?



Harold Ritter Mon, 03/30/2009 - 07:48

Hello Mohammed,

I'm glad I have this opportunity to discuss this very interesting topic with the NetPro community.

1. Although the standards are there, I know very few commercial implementation of MPLS support for native IPv6. It will certainly come as demand for it grows.

2. As you mention, there are several ways to deploy IPv6 over an MPLS core.

a) 6PE is very easy to deploy and is appropriate for a SP that need to deploy transit IPv6 services. Only the PEs being used for IPv6 peering or transit need to be configured for IPv6.

b) 6VPE provides the equivalent to MPLS VPN (l3vpn) for IPv4.

c) AToM just provides a piece of wire between two sites, which means that the customer can carry whatever they'd like on it, which makes it appropriate if you can't afford or don't want to configure IPv6 on the PE.

d) Do you mean just ipv4 l3vpn with ipv6 over ipv4 tunnels between the PEs. If so, this also provides a quick way for users to migrate to IPv6 without any additional configuration on the provider's behalf.

Running dual stack on the PE largely depends on the SP plan and strategy toward IPv6 but I would strongly advise that any SP should at least have a well thought plan to deploy IPv6 at this point.


beth-martin Tue, 03/31/2009 - 16:44

What would be the easiest way to provide IPv6 services to my customers if my core network is IPv4 only?

Harold Ritter Tue, 03/31/2009 - 18:57


Well, it depends whether your core is MPLS enabled or not. If it is then the easiest way to provide IPv6 transit services is 6PE as I mentioned in my previous post. 6PE only requires enabling IPv6 on the edge routers connecting the customers requesting IPv6 services and on the transit or peering routers. 6PE allows IPV6 traffic to be forwarded through your IPv4/MPLS without having to enable IPv6 in your core network.

If your core is not MPLS enabled, here are some suggestions.

1. Enabling IPv6 on all of your routers (dual stack). This will definitely position you well for the future.

2. Enabling IPv6 on your core routers and on the edge routers where it is required. This will provide for a smoother transition than the previous approach.

3. Enabling IPv6 on the edge routers where it is required and tunnel IPv6 traffic over IPv4 to the transit or peering routers. You can then enable IPv6 on your core routers over time. This will also allow for a smoother transition.

4. Enabling MPLS in your network and provide IPv6 transit services using 6PE. This will obviously require more work but will allow to also offer a slew of MPLS enabled services to your customers.


devang_etcom Tue, 03/31/2009 - 20:37


Finally you are in IPv6 discussion expert talk!

As usual native support for MPLS in IPv6: when cisco is planning for it?

To me I know its not gona make big difference as all the application is supported in PE and you can tunnel it via IPv4 native supported MPLS tunnels.

And any better techniques for service providers network to migrate from IPv4 to IPv6? I mean during adding any MPLS application how can we migrate from IPv4 to IPv6?


Devang Patel

Harold Ritter Wed, 04/01/2009 - 05:59

Hi Devang,

The demand for MPLS support for native IPv6 will obviously come as more native IPv6 networks are built. I know of a few right now mainly in Asia Pac but most IPv6 deployments I see right now are dual stack hence no major pressure for MPLS support for native IPv6.

About you second question, providing IPv6 services over MPLS is really easy and allows you to slowly migrate your core to IPv6. This will give you time to deploy IPv6 on your core routers one by one. Once all of you core routers have incorporated IPv6 support you can transition your edge nodes from 6PE to native IPv6 if you'd like. This again can be done over a period of time an don't need to be done in a rush.


devang_etcom Wed, 04/01/2009 - 12:01


Now as far as core IGP is concern, what will you prefer to do? I m just asking in general!!!

As OSPF running core still need to support OSPFv3 to support IPv6 on the other end running ISIS is need to add only IPv6 configuration for links.


Devang Patel

Harold Ritter Wed, 04/01/2009 - 13:08


I personally recommend using different routing instances for IPv4 and IPv6. This way IPv4 and IPv6 runs as ships in the night and instability in one doesn't affect the other.

ISIS doesn't currently support that but there is a draft in the IETF for the support of multi-instance ISIS.

Nothing would stop you from using ISIS for V4 and ospfv3 for V6 though.


devang_etcom Fri, 04/03/2009 - 11:00


In ISIS we have Multitopology feature right which will be helpful to keep our IPv4 and IPv6 addressing topology separated, right?

As well as few more advance level consideration: as Core technology like mLDP and RSVP extension for multipoint is there in IPv4 so are they going to available soon in IPv6 or will it take some time?

Can you provide some good documentation about the IPv6 addressing, migration and deployment scenarios for both service provider and enterprise level?

As well as what are the hardware limitation did you encounter during your IPv6 deployment; as IPv6 addressing is larger than the IPv4 so I guess memory will be the big consideration right? so other than that what are the other consideration?


Devang Patel

Harold Ritter Fri, 04/03/2009 - 14:39


DP> In ISIS we have Multitopology feature right which will be helpful to keep our IPv4 and IPv6 addressing topology separated, right?

Bear in mind that multi topology doesn't offer a complete separation between IPv4 and IPv6 if for some reasons there is some instability in one protocol, the other might suffer from it as well.

DP> As well as few more advance level consideration: as Core technology like mLDP and RSVP extension for multipoint is there in IPv4 so are they going to available soon in IPv6 or will it take some time?

Basic LDP and RSVP support for native IPv6 is currently not available. These and the more advanced features will definitely become available when demand for them grows.

DP> Can you provide some good documentation about the IPv6 addressing, migration and deployment scenarios for both service provider and enterprise level?

The following URL is a good source of information for deployment strategies.

The following book has been written by some of my colleagues, who have been working and deploying IPv6 for years and have been involved with some large deployments. I hear lots of good things about it.

DP> As well as what are the hardware limitation did you encounter during your IPv6 deployment; as IPv6 addressing is larger than the IPv4 so I guess memory will be the big consideration right? so other than that what are the other consideration?

Although most IPv6 enabled network do not experience heavy IPv6 traffic load, all high end routers forward IPv6 in HW at line rate. You just need to scope the HW you need appropriately.

I would say that the biggest challenge with memory currently is mostly related to the ever increasing IPv4 routing table size. Adding IPv6 doesn't help but the size of the IPv6 routing table is rather modest but it will certainly grow as more and more people migrate to IPv6.

You can go to the following site to get some interesting statistics about the IPv4 and IPv6.


devang_etcom Fri, 04/03/2009 - 17:05

Thanks Harold for your reply!

It seems still lots of work remaining for IPv6. As far as VPN service to IPv6 customer is not an issue as you can have 6PE/6VPE kind of technologies to deal with that but the service provider offering the IPTV kind of services they still have to wait little more for fully IPv6 deployed core network.

thanks again,

Devang Patel

Harold Ritter Fri, 04/03/2009 - 18:07


The number of new IPv6 features is impressive and obviously their implementation have to be prioritized according to customer demand and business cases.

If there is anything you feel you need in the short term, I would encourage you to talk to your account team. They will be able to convey your requirements back to our development team, which will then reprioritize their road map as needed.

Thanks for your comments.


Harold Ritter Sat, 04/04/2009 - 04:09


Just out of curiosity, was there any additional features other than mLDP and MPLS P2MP tunnels that you think you would require to deploy IPTV services over an IPv6 network. I know of a few very successful large scale IPTV deployments over IPv4 that have been in production for a few years now and that don't use mLDP and MPLS TE P2MP tunnels. So in my view, one should be able to replicate the experience with IPv6 today.


devang_etcom Sun, 04/05/2009 - 12:29


In IPTV deployment there are multiple services like Video on Demand (VOD), live streaming, etc. VOD is unicast base so MPLS FRR kind of thing is must to have fastest failover. BFD support for IPv6 is there but I am sure there is nothing like FRR. So to me It is really very important to have native IPv6 MPLS support with LDP and RSVP is must.

I am just putting my thoughts, there might be some different cases. Currently IPv6 technology at Service Provider end is fulfilling need for Enterprise customer (Corporate world). To reach End user customer via VOIP/IPTV and Data service on DSL or CABLE will need to wait for the IPv6 reach feature sets in deployment.

Harold, I noticed that you are always there to resolve any issue or providing your quick thoughts as well as exploring the details of any topics. I also noticed your analysis skill during troubleshooting of various MPLS related topics in discussion forum. It is good to have an expert like you on discussion forum.


Devang Patel

Harold Ritter Mon, 04/06/2009 - 04:05


The requirement for MPLS for native IPv6 depends on your deployment strategy but as I said there is IPTV over IPv4 deployments out there not using MPLS at all. You could start deploying IPTV in an IPv6 network today and use MPLS FRR once it becomes available. In the meantime, you can use fast convergence technique to provide a quality service to your customers.

As far as I know, IPv6 support for Cable is available on the UBR7200 and UBR10k. IPv6 support for DSL is available depending on the platform you use.

Thanks for the kind comments. It is always a pleasure for me to get to discuss these interesting topics with the NetPro community.


devang_etcom Thu, 04/09/2009 - 21:16


Hummm, can you share some documentation or any kind of guide line having IPTV deployment with out MPLS in network. I heard that some deployments are there, I have my IPTV deployment experience there we were using MPLS application to make it very efficient. The deployment I worked on was not Cisco deployment, it was Alcatel deployment.


Devang Patel

Harold Ritter Fri, 04/10/2009 - 03:57


I do not have any document I can share about these deployments but what I can say is that they were using IP fast convergence in the core rather than MPLS.

I would recommend that you google on "IPTV on IPv6". You will find a lot of articles and project announcements indicating that some companies are already moving forward with this technology, despite the fact that MPLS is not currently available for native IPv6.


tenaro.gusatu.novici Wed, 04/01/2009 - 06:14

Hi there,

before I start, let me first warn you that I'm complete rookie in the IPv6 world. Saying that I do have couple questions regarding IPv6:

- Is there something like world wide IPv6 network/backbone that exists in paralel with our IPv4 internet?

- How can I request IPv6 addresses for my company? Is it again going through my ISP or I can demand this somehow directly from RIPE? Somehow I'm very sceptic that my ISP knows anything about IPv6...

I don't see any benefit in enabling IPv6 inside company even if I know XP and Windows Server 2008 supports dual stack and IPv6 just as Cisco routers. It will help if you can give me some reasons why should I move to IPv6. BTW, as far as I know, Cisco IP telephony is not (yet) supporting IPv6...

I hope my questions are not out of the scope for this topic.



Harold Ritter Wed, 04/01/2009 - 11:05


Welcome to the discussion.

- There is an IPv6 enabled Internet just like there is an IPv4 Internet. It is maintained or operated by most of the same service providers (SP) and uses most of the same infrastructures.

There used to be an experimental IPv6 network called the 6bone that was put together to foster the adoption of IPv6. The 6bone has been decommissioned on June 6th 2006.

- There is two ways in which you can get IPv6 address space. You can either go to a SP and get a /48 prefix out of their /32 block or go to one of the Regional Internet Registries (RIR), namely ARIN, RIPE, APNIC, LACNIC or AfriNIC) and get a Provider Independent (PI) block. The second approach is more convenient if you intend to have multiple upstream service providers.

If your provider is currently not IPv6 enabled, you might have to inquire about their plan to deploy IPv6 or look around for provider(s) that already offers IPv6 transit.

As for your question on why you would move to IPv6, if you are an enterprise network, I don't see any urge to deploy IPv6 but I would suggest you start planning for it and getting familiar with the technology. On the other hand, I would say that any serious SP should at least have a plan of action to get there and should start executing it.

Most Operating Systems and networking gears currently support IPv6.

I am not sure where we stand on IPv6 support for the Call Manager but I know most of the recent IP phones support IPv6. As for the rest of the Cisco IP Telepnony components, I'm sure there is a roadmap for them if they don't already support IPv6.

Those were all very good questions and your concerns are share by many of our customers these days.


cisco4kaleem Mon, 04/06/2009 - 00:56


As there is a plan to upgrade from IPV 4 to IPV 6 want to make sure if the system need to be upgrade to support IPV 6

the version of Rogger A,B is MS Win 2003

AWSA and B MS wind 2003

CM A&B is 4.1 Windows 2000

IVR A and B Windows 2000

1. Current systems readiness for understanding the packet format of IPV6. This covers HW, SW (OS and DB), and Application

2. Current systems readiness for migrating to the new IPV6. This covers HW, SW (OS and DB), and Application

Appreciate early response.

Harold Ritter Mon, 04/06/2009 - 10:41


I would suggest you contact your account team to find out the exact availability or road map for Unified Communication products.


princekujerouss Thu, 04/09/2009 - 23:46

God Morning my name is Ayoyemi Kujero

I want to Know the Recommended Books for IPV6 and also the Recommended Books for Token Ring and ATM

Harold Ritter Fri, 04/03/2009 - 13:51


Excellent question. Anycast RP, as we currently know it in the IPv4 world is not supported in IPv6. The reason is that Anycast RP generally requires MSDP to synchronize the different RPs in the domain and MSDP has not been defined for IPv6 and will not be either. It would still be possible to use Anycast RP without MSDP, as defined in RFC4610. This is not currently available though.

It is currently possible to run static RP (or embedded RP) and to get redundancy. The one techniques I know is to to have multiple RPs advertising the same address but to have one advertising it with a longer prefix length. Unlike Anycast RP, where first hop routers register to the closest RP, this technique doesn't offer load sharing but at least it does offer redundancy.


b.hsu Wed, 04/08/2009 - 11:07

Why is it that I need to have and IPv4 DNS to resolve my IPv6 host name lookup.

Harold Ritter Wed, 04/08/2009 - 13:58


Your DNS servers use what is referred to as a "A record" for hostname to IPv4 address resolution.

In the other hand, the host name to IPv6 address resolution uses a AAAA records. In the simplest case, you would need to add a AAAA record to your DNS server for the host name you need to be resolved to an IPv6 address.

If you use an OS like windows XP with dual stack, the workstation sends both an IPv6 and IPv4 host name resolution request. It will attempt to use the IPv6 address first and then the IPv4 address if the IPv6 address doesn't exist.

Obviously, workstations that have a single stack (IPv4 or IPv6) will query the DNS with their respective host name to IP address resolution.

By having both the A and AAAA records configured in your DNS server, you will ensure that both IPv6 and IPv4 hosts will be able to access a given resource. This resource will need necessarily need to be dual stack.



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