IPV6 nat

[Stuart Gall]

I have a number of sites were I have used multiple aDSL lines to increase bandwidth for the users.

We looked at costs several times and this was a more cost effective way to go.

So this all works by having a load balancing device and then using NAT overload on the gateway routers.

What should I do when I go over to IPV6 ?

I don't have to overload. But I dont see any way around using unique local addresses and then NAT on each router. Right ?

Is there any alternative ?

In that case

Is there a way I can (in IOS) do NAT so that each unique local address is maped onto a coresponding Global unique address and not just any old address from the pool

FC00::1234:5678/64 is mapped to 3FFF:FFFF::1234:5678/64

FC00::AAAA:BBBB/64 is mapped to 3FFF:FFFF::AAAA:BBBB/64

[sean_evershed]

NAT for IPv6 is not recommended - see RFC 2993 for details.

Unique local addresses are not recommended for organisations that intend to connect to the Internet - see RFC 4193 for details.

My suggestion is to use global IPv6 addresses in your network. Have a look at the following links for details:

- Service Provider IPv6 Deployment, https://supportforums.cisco.com/docs/DOC-21124

- Cisco whitepaper, “What Enterprises are doing about IPv6 in 2011”,

http://www.cisco.com/en/US/prod/collateral/iosswrel/ps6537/ps6553/whitepaper_c11-586154.html

The Cisco Press book "IPv6 for Enterprises" is also an excellent reference for IPv6.

Don't forget to rate posts that are helpful.

[Stuart Gall]

Hi Sean, Thank you for your reply.

Load balancing is a requirement for many small business where 4aDSL lines might cost $200 / month but a leased line is more like $2000 / month. (at least in my part of the world)

So there has to be a recommendation for these scenarios yet as far as I can see there just isn't. Except to say (as you did) don't use NAT.

Salaman does offer SiteLocal + UniqueGlobal as one possible solution.

I have been doing some more research on the subject

In RFC4861 (NDP) it says this

Inbound load balancing - Nodes with replicated interfaces may want

           to load balance the reception of incoming packets across

           multiple network interfaces on the same link.  Such nodes

           have multiple link-layer addresses assigned to the same

           interface.  For example, a single network driver could

           represent multiple network interface cards as a single

           logical interface having multiple link-layer addresses.

So from this I infer that the practice on IPv6 would be to have multiple routers each serving a specific internal unique-local address space. And then have each host with multiple addresses and let the host do the load balancing.

The problem with this is that the only distribution policy is random. (You cant do sequential or load sensitive)

Perhaps ISPs will recognise this requirement and provide load balancing over aDSL now that we have the addresses to do it.

[patoberli]

Actually I think ISPs will recognise this business oportunity and offer you to finaly buy their leased lines instead of their "home usage, cheap adsl" lines
So I'm pretty sure ISPs wont do anything, besides being happy, that load balancing isn't anymore really working.