DS-Lite – Provision for IPv4 Blocks to CPE by ISPs

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I run a small ISP for a rural community in England. There are around 350 residential properties and 15 small businesses. Three of these businesses run systems that require two consecutive IPv4 addresses – it is some sort of EDI system for taking orders, but I don't know the details.

There is currently no IPv6 provision at all. Until very recently our upstream provider has only made IPv4 space available.

I am considering options to deploy IPv6. DS-Lite is one of the options, although I am at the research stage.

https://benunetworks.com/new-products/dual-stack-lite/ would suggest that ISPs that deploy DS-Lite will be unable to route IPv4 blocks to their clients as CGNAT is performed in the provider network.

Is this a true reflection of the technical reality? I would like to be as IPv6 native as possible – the attraction to DS-Lite – but I still need to let business customers do their own NAT for IPv4.

I am hoping someone has deployed DS-Lite and will be able to enlighten me.

Best Answer

As I explained in my comments, CGN and DS-Lite are for residential customers. You should not deploy these to your business customers. Continue to serve your business customers as you do today, but deploy CGN or DS-Lite for your residential customers.

RFC 6333, Dual-Stack Lite Broadband Deployments Following IPv4 Exhaustion explains how DS-Lite works:

This document revisits the dual-stack model and introduces the Dual- Stack Lite technology aimed at better aligning the costs and benefits of deploying IPv6 in service provider networks. Dual-Stack Lite enables a broadband service provider to share IPv4 addresses among customers by combining two well-known technologies: IP in IP (IPv4- in-IPv6) and Network Address Translation (NAT).

If your business customers need to have exclusive use of a public IPv4 address, then you cannot use CGN or DS-Lite for the business customers.

You also should have already been providing IPv6 to both your residential and business customers for several years now. You should look at RFC 6177, IPv6 Address Assignment to End Sites and the other IETF recommendations for that. Each business customer site should get no longer than a /48 IPv6 prefix, and residential customers should get something smaller than a single /64 prefix (/56 is fairly common for residential customers).

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