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Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

[IPv6] Setting up a Local v6 network using Comcast IPv6

I have a question for those v6 geeks out there. How are you setting up your local networks?

I'd like to set up a few devices on my home network to use static addresses with v6. Since I'm using v6 with Comcast PD, it's only a matter of time before my prefix expires and Comcast assigns me a new Prefix. Needless to say, I do not want reassign all my devices new IPs and update all the records in my local DNS server when this happens.

My plan is to use LinkLocal addresses for all internal communication on my small home network and allow my devices to communicate to the internet using Global addresses.

Example:
fe80::1000 computer1
fe80::1001 computer2
etc.

Is this the proper way to handle this situation? Would this also be considered best practice?


AVonGauss
Premium
join:2007-11-01
Boynton Beach, FL

1 recommendation

You definitely don't want to use manually created link local addresses. While you probably won't enter one that would be automatically generated, it does go against the intent.

If you do want to use a private IPv6 range similar to IPv4 land, you would want a unique local address.

»en.wikipedia.org/wiki/Unique_local_address

The easiest way would be start a separate RADVD prefix section and/or instance and let the equipment grab the additional prefix (i.e. FD00) and then add the addresses as static entries to your DNS server.



Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

Ahh really good reply. Thanks

So it would be better to do some sort of IP Reservation for the unique local addresses?

Do you happen to know if there is an equivalent to this in Cisco land? I have a Cisco 881 at my home I'm trying this with.


AVonGauss
Premium
join:2007-11-01
Boynton Beach, FL

I'm not the best person to ask regarding the Cisco, I muddle through myself every single time I have to do something on one. If you're using RAs its not really a reservation, so much as capturing the address. You could also do an actual reservation using DHCP, but I would check to make sure the devices support it.

Server and infrastructure using IPv6 static addresses, worked for years. Workstations grabbing an IPv6 address to browse or use the Internet, has worked fairly well for a while now. The "in between", still can be a tad rough.



NetDog
Premium,VIP
join:2002-03-04
Parker, CO
kudos:77
Reviews:
·Comcast
reply to Clever_Proxy

What I would like to see is support like this in OS. I would like to set the host part of an IPv6 address and have the OS use the RA to get the Prefix address. If you combine the two you get your IPv6 address.

RA Prefix + user defined host IP = IPv6 address for the host

VMWare supports this today, and I do this with my linuxes boxes using a script that runs hourly.



Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

Yes, exactly!

It's seeming like what I'm trying to accomplish is a little on the "hacky" side. Seems like device/OS support for truly going to the v6 side still needs a little work.

In the meantime, I think I need to study up on RAs vs DHCP. I don't fully understand the concept yet.

I'm sure I'll be back with more questions. Thanks!



NetDog
Premium,VIP
join:2002-03-04
Parker, CO
kudos:77
reply to Clever_Proxy

Feel free to ping me, lots of information on this subject out on the interwebs. But if you have issues finding what your looking for post on this forum lots of good people here to answer questions.



Clever_Proxy
Premium
join:2004-05-14
Villa Park, IL

1 edit

Thanks NetDog. You never fail to go above and beyond to help out.

I'm starting to get a better understanding of what I'm trying to do. I found a really good Cisco document that explains Link-Local/Unique-Local/RAs very well. Here's what made it clear as day for me.

»www.cisco.com/en/US/docs/ios-xml···43DAD0EB

Link-Local Address

A link-local address is an IPv6 unicast address that can be automatically configured on any interface using the link-local prefix FE80::/10 (1111 1110 10) and the interface identifier in the modified EUI-64 format. Link-local addresses are used in the neighbor discovery protocol and the stateless autoconfiguration process. Nodes on a local link can use link-local addresses to communicate; the nodes do not need globally unique addresses to communicate. The figure below shows the structure of a link-local address.

IPv6 devices must not forward packets that have link-local source or destination addresses to other links.


Unique-Local Address

A unique local address is an IPv6 unicast address that is globally unique and is intended for local communications. It is not expected to be routable on the global Internet and is routable inside of a limited area, such as a site. It may also be routed between a limited set of sites.

A unique local address has the following characteristics:

-It has a globally unique prefix (that is, it has a high probability of uniqueness).
-It has a well-known prefix to allow for easy filtering at site boundaries.
-It allows sites to be combined or privately interconnected without creating any address conflicts or requiring renumbering of interfaces that use these prefixes.
-It is ISP-independent and can be used for communications inside of a site without having any permanent or intermittent Internet connectivity.
-If it is accidentally leaked outside of a site via routing or DNS, there is no conflict with any other addresses.
-Applications may treat unique local addresses like global scoped addresses.


Autoconfig and RAs are actually really neat and unique features of v6. It will be neat to see how it evolves.

Anyways, I've been looking over the IOS specs for DHCPv6. It looks like what I'm trying to accomplish is very possible. What I'm going to attempt to accomplish is:

- Each machine have a Global address assigned using Comcast PD (this is already working)
- Each machine have a Unique local address assigned using DHCPv6 on the IOS router with reservations (most likely will be a /64 prefix)
- Each machine will have a v6 Link-Local address assigned using the autoconfig methods already in place

So in the end, every device on my network will have 3 v6 addresses. Seems a little overkill, but that just seems to be the nature of v6.

Another thing to think about is my default gateway. I'm more than likely going to be assigning a Global default gateway. I don't anticipate having more than one subnet on my little home network, but on more of a small/enterprise class level it's a very real possibility. This could cause an issue of computers routing packets to the wrong interface and we would be relying on routing or layer 3 switching to correct this issue.

If I get this to work, I'll post my IOS config with interface results.


AVonGauss
Premium
join:2007-11-01
Boynton Beach, FL

If the link-local addresses are consistent for your devices, you could skip the unique local if you don't need routing and just enter the link-local in to your DNS. The downside is you're unlikely to know just by the address what device it is (i.e. not a high chance of remembering each link-local address). If that's not a concern, that's one less addressing scheme to maintain.



NetDog
Premium,VIP
join:2002-03-04
Parker, CO
kudos:77
Reviews:
·Comcast
reply to Clever_Proxy

I only have ULA's(Unique local address) on devices that I don't want to talk to the internet. My phones are an example, they don't need to talk direct to the internet, they only talk to my Cisco Call MGR.

I have heard of people having issues with a GA (Global Address) and a ULA address on a PC. So keep that in mind..


bigjoesmith

join:2000-11-21
Peoria, IL

1 recommendation

reply to AVonGauss

said by AVonGauss:

If the link-local addresses are consistent for your devices, you could skip the unique local if you don't need routing and just enter the link-local in to your DNS. The downside is you're unlikely to know just by the address what device it is (i.e. not a high chance of remembering each link-local address). If that's not a concern, that's one less addressing scheme to maintain.

I agree. I'm a fan of keeping it simple. IPv6 auto configuration does a lot of work and you can find yourself swimming against the current if you bring some IPv4 thinking over.

»technet.microsoft.com/en-us/maga···guy.aspx is an interesting read on IPv6 address configuration in general and for Windows in specifics.