Prefix delegation to sub nets

Kristian McColm Kristian.McColm at
Sun Jun 27 21:04:42 CEST 2021

RFC 5375 advises against prefixes longer than /64.

A /48 gives you 65535 /64’s, why not use some of them?

From: at < at> on behalf of Doug Hardie <bc979 at>
Sent: Sunday, June 27, 2021 2:54:01 PM
To: ipv6-ops at <ipv6-ops at>
Subject: Prefix delegation to sub nets

I am trying to setup an IPv6 environment.  There is a primary router (A) that receives a /48 prefix via DHCP6 from the ISP. That router configures itself properly via dhcp6c.  It also creates 2 LAN /64 prefixes and creates EUI-64 addresses on the two LAN interfaces.  One of those interfaces is connected to a second router (B), among other devices.  The B router receives the prefix via SLAAC and creates its own EUI-64 address.  However, that router needs to create a smaller subnet, /72, and distribute it to the devices on that LAN.  I have not been able to figure out how to make that happen.

Clearly, manual configuration would work, but the prefix received from the ISP can change which would raise havoc with the network.  I suspect that dhcp6s needto be run alongside dhcp6c on router B and then the other devices run dhcp6c.  However, I don't see how to get the prefix that dhcp6c receives on router B to the dhcp6s process on router B.  I believe I am missing something, but haven't been able to find it.  Thanks,

-- Doug

This communication is confidential. We only send and receive email on the basis of the terms set out at<>

Ce message est confidentiel. Notre transmission et réception de courriels se fait strictement suivant les modalités énoncées dans l’avis publié à <>
-------------- next part --------------
An HTML attachment was scrubbed...

More information about the ipv6-ops mailing list