[GLLUG] IP address problems.

[Chris Bell]

Hello,
"Every interface can have multiple IPv6 addresses, while multiple interfaces 
can respond to a single IPv6 address."
Unfortunately I find that boxes generally forget all but the last IPv6 address 
allocated remotely.

I have multiple networks behind a firewall and want to allocate local IPv4 NAT 
addresses, 2001::/16 global IPv6 addresses, and local fd00::/8 IPv6 addresses, 
all of which which will survive a re-boot. All regular boxes are running up-
to-date Debian 10 Buster with or without KDE, and the RaspberryPi boxes are 
running the equivalent RaspberryPi version of Debian Buster, although some 
started as Raspbian while others the more recent Raspbios.

My ISP Plusnet has failed to provide IPv6 as promised, and my contract does 
not expire until next March. I have tried to configure an IPv6 in IPv4 tunnel 
via Hurricane Electric, but it is not yet working through my firewall. I have 
also followed the instructions in RFC 4193 to generate local IPv6 addresses, 
but they have frequently been forgotten after a re-boot.

My firewall is running dnsmasq and RADVD, and I have another box running bind9 
which should be available locally.
I can use "ip address add" for IPv6 addresses, but they have not always 
survived a re-boot.
I have tried entering all IPv4 and IPv6 addresses in /etc/network/interfaces 
but with inconsistent IPv6 results, although I have had some success using 
files in /etc/systemd/network/...

The RaspberryPi default is to use /etc/dhcpcd.conf to specify either a set of 
static addresses or a set of static fallback addresses, but the name of the 
ethernet device has not been consistent. The device name read from "ip address 
show" has varied over time between "eth0", and "enx" followed by the twelve 
HEX characters of the MAC address without any ":". The configuration fails 
every time the device name changes, although I have found that the MAC address 
does correctly match the hardware following a change of MicroSD.
-- 
Chris Bell
Website http://chrisbell.org.uk