On Jan 26, 2012 5:49 AM, "Owen DeLong" <owen@delong.com> wrote:
On Jan 26, 2012, at 2:00 AM, George Bonser wrote:
Use different GUA ranges for internal and external. It's easy enough to get an additional prefix.
As others have mentioned, things like management interfaces on access switches, printers, and IP phones would be good candidates to hide with ULA.
Or non-advertised, filtered GUA. Works just as well either way.
Owen
If one is obtaining "another" prefix for local addressing, I see no
benefit. I am assuming that anyone that is using ULA is using it for things that don't communicate off the site such as management interfaces of things, etc. This won't be a subnet you are connecting by VPN to another organization, usually, but even if you do the chances of collision is pretty low if you select your nets properly. But for the most absolutely paranoid site, I can see some appeal in using ULA in conjunction with DNS64/NAT64 and see them giving the devices internet access via v4. Not that I agree with the notion, mind you, just that I can see someone looking at that as an appealing solution for some things. Even if someone managed to get through the NAT device via v4, they would have nothing to talk to on the other side as the other side is all v6.
Even if you don't see an advantage to GUA, can you point to a disadvantage?
IMHO, it would be far less wasteful of addressing overall to deprecate fc00::/7 and use unique secondary GUA prefixes for this purpose than to use ULA.
If you can't point to some specific advantage of ULA over secondary non-routed GUA prefixes, then, ULA doesn't have a reason to live.
1. You don't want to disclose what addresses you are using on your internal network, including to the rir 2. You require or desire an address plan that your rir may consider wasteful. 3. You don't want to talk to an rir for a variety of personal or business process reasons 4. When troubleshooting both with network engineers familiar with the network as well as tac engineers, seeing the network for the first time, ula sticks out like a sore thumb and can lead to some meaningful and clarifying discussions about the devices and flows. 5. Routes and packets leak. Filtering at the perimeter? Which perimeter? Mistakes happen. Ula provides a reasonable assumption that the ISP will not route the leaked packets. It is one of many possible layers of security and fail-safes. Cb
I'm not sure where DNS64/NAT64 comes into play here for v6 to v6 communication. For IPv4, I don't see any advantage in ULA+NAT64 vs. the more reliable and easier RFC-1918 with NAT44 possibilities, even if you have to run multiple RFC-1918 domains to get enough addresses, that will generally be less complicated and break fewer things than a NAT64 implementation.
Owen