Re: [nznog] What's the BCP/RFC that says that routers within an ISP network should not have RFC1918 link IPs?

Yeah, DS Lite requires CPE support, so it’s a non-starter for most NZ providers. Last time I looked at it, which was a few years ago admittedly, there was no backwards compatibility - a provider had to transition all customers to DS-L, and IPv4-only service was no longer possible. Its key benefit is to “eliminate” double IPv4 NAT, but, that isn’t important and it doesn’t actually achieve it. I looked at some data with someone (who I won’t name but they might like to implicate themselves) that showed that something like 20% of outbound packets from a medium sized NZ ISP had a set of TTL values that indicated double-NAT (or an extra routing hop but that doesn’t seem that likely), in the customer premise. Something like 3% had more than two. That’s % of packets, not % of users. I’m unsure whether it’d be higher or lower if it were % of users. Anyway, given that, it’s my view that an extra NAT hop isn’t going to negatively impact the majority of customers. Sure, it’s bad for the Internet etc. etc. but we’re already there and almost all applications deal with it already. If a customer needs a “port forward”, they’re not going to get that with DS-Lite any easier than they are with an extra NAT hop in the ISP. On 27/02/2014, at 2:00 pm, Lindsay Hill wrote:

The key problem with DS-Lite that I see is that it requires CPE config - it's just too much hassle. Seems to be easier to go for CGN (with all the problems that entails).

On Thu, Feb 27, 2014 at 1:52 PM, Lloyd Parkes wrote:

On 27/02/2014, at 12:13 pm, Neil Fenemor wrote:

...

As an ISP'll end up with collisions with their customers if RFC1918 space is used for their intermediary/ISP portion of NAT444, a new /10 (specifically 100.64.0.0/10) was allocated for this use. RFC6598 details the allocation, and the use cases for it.

Is there anyone here who has had to choose between CGN and dual-stack lite and is willing to say why they made the choice they did. I’m familiar with the various possible issues and I’m interested in hearing about what people’s actual issues have been.

Cheers, Lloyd

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