I have become fascinated by prefix delegation and ipv6 subnetting - to
the extent that I have decided to learn more about it. I have set up the
following test network using VirtualBox: (main router is a real host;
the virtual hosts (Netn) run on my workstation)
Internet
|
|
------------
| |
|Main router|
| |
-------------
LAN
|
|
| enp0s3
-----------
| |
| Net0 |
| |
-----------
enp0s9 | | enp0s8
| |
| --------------------
| |
| enp0s3 | enp0s3
----------- ----------
| | | |
| Net1 | | Net2 |
| | | |
----------- ----------
enp0s8 |
|
| enp0s3
-----------
| |
| Net4 |
| |
-----------
I have also decided that I want to use networkd for the purpose because
I like the idea of systemd and networkd.
So far I have encountered two problem areas: 1) getting prefix
delegation to work and 2) getting IP6 downstream routes set up. I'll
return to the route setup problem in a later post.
The prefix delegation problem starts with the interactions between net0
and net2. Net0 is delegated a /56 prefix from the main router (which
runs radvd and dhcpd6, not networkd, for historical reasons). I want
net2 to delegate a /60 subnet to net3, but it doesn't happen. The
immediate symptoms are that net0 doesn't start a dhcp6 server on
downstream interface enp0s9 and net2 doesn't start a dhcp6 client on
upstream interface enp0s3.
The hosts net0, net2 and net3 all run ArchLinux (kernel5.18.5-arch1-1,
systemd 251.2-1). Here are the configuration files:
Host net0:
=====
# Upstream interface enp0s3 on net0
[Match]
Name=enp0s3
[Network]
# SLAAC IPv6 for obtaining the default route.
LinkLocalAddressing=ipv6
DHCP=yes
[IPv6AcceptRA]
DHCPv6Client=yes
=====
=====
# Downstream interface enp0s8 on net2
[Match]
Name=enp0s8
[Network]
DHCPPrefixDelegation=yes
IPv6SendRA=yes
IPv6AcceptRA=no
IPForward=yes
DHCPServer=yes
[DHCPPrefixDelegation]
UplinkInterface=enp0s3
SubnetId=8
Announce=yes
[Address]
Address=192.168.1.1/24
[DHCPServer]
PoolOffset=90
PoolSize=10
EmitDNS=yes
BindToInterface=yes
#[DHCPServerStaticLease]
# Net3 - IF enp0s3
#MACAddress=08:00:27:d7:6b:82
#Address=192.168.1.100
========
Host net2:
=====
# Upstream interface enp0s3 on net2
[Match]
Name=enp0s3
[Network]
LinkLocalAddressing=ipv6
# SLAAC IPv6 for obtaining the default route
IPv6AcceptRA=yes
DHCP=yes
IPForward=yes
[DHCPv4]
Hostname=net2
UseHostname=no
# Ignore the hostname from the DHCP server
UseDNS=yes
UseNTP=yes
UseRoutes=yes
UseGateway=yes
[IPv6AcceptRA]
UseDNS=yes
DHCPv6Client=yes
[IPv6PrefixDelegation]
Managed=yes
[DHCPv6]
ForceDHCPv6PDOtherInformation=yes
UseHostname=no
UseDNS=yes
UseNTP=yes
=====
And here are the symptoms that to me doesn't look right:
On host net0:
[root@net0 ~]# ss -l6
Netid State Recv-Q Send-Q Local
Address:Port Peer Address:Port Process
icmp6 UNCONN 0 0 *%enp0s3:ipv6-icmp *:*
icmp6 UNCONN 0 0 *%enp0s8:ipv6-icmp *:*
icmp6 UNCONN 0 0 *%enp0s9:ipv6-icmp *:*
udp UNCONN 0 0 [fe80::a00:27ff:fe8b:3d3]%enp0s3:dhcpv6-client
[::]:*
udp UNCONN 0 0 [::]:llmnr [::]:*
tcp LISTEN 0 128 [::]:ssh [::]:*
tcp LISTEN 0 511 *:https *:*
tcp LISTEN 0 80 [::]:mysql [::]:*
tcp LISTEN 0 4096 [::]:llmnr [::]:*
tcp LISTEN 0 511 *:http *:*
[root@net0 ~]#
I'm missing a dhcpv6-server on enp0s8 (and enp0s9 for that matter)
Similar for host net2:
[root@net2 ~] ss -l6
Netid State Recv-Q Send-Q Local Address:Port Peer Address:Port Process
icmp6 UNCONN 0 0 *%enp0s8:ipv6-icmp *:*
icmp6 UNCONN 0 0 *%enp0s3:ipv6-icmp *:*
udp UNCONN 0 0 [::]:llmnr [::]:*
tcp LISTEN 0 4096 [::]:llmnr [::]:*
tcp LISTEN 0 128 [::]:ssh [::]:*
[root@net2 ~]
Here I'm missing a dhcpv6-client on enp0s3.
I do need somebody to discuss these matters with since my thought
sometimes appear to run in circles. I hope somebody will take the time
to comment on this. Also I do apologize for the lengthy post but these
matters are complicated - at least to me.
Kind regards
Bent
