Problem with dhcpv6 and systemd-networkd clients

Tue Apr 7 15:52:40 UTC 2020

This bit here:

Apr  7 15:54:20 prokyon dhcpd[9823]: Discarding Request from fe80::230:5ff:fec9:38ff; not our server identifier (CLIENTID 00:02:00:00:ab:11:71:bc:09:50:c1:3c:0b:51, SERVERID 00:03:00:01:00:1d:aa:97:f0:44, server DUID 00:01:00:01:26:1f:32:19:02:a5:04:3d:96:27)

indicates that some other server is answering as well (or the client thinks it is).  Could that be the case?  Is dhcpd configured and running elsewhere?

----- Original Message -----
> From: "Robert Senger" <robert.senger at lists.microscopium.de>
> To: "Users of ISC DHCP" <dhcp-users at lists.isc.org>
> Sent: Tuesday, April 7, 2020 10:18:29 AM
> Subject: Problem with dhcpv6 and systemd-networkd clients

> Dear all,

> I just discovered a problem with two clients that use systemd-networkd
> for network configuration.

> Both clients, as well as the dhcp server, run Debian 10.

> Both clients have their network interfaces in /etc/systemd/network
> configured like this:

> File /etc/systemd/network/10-eth0.network
> ---
> [Match]
> MACAddress=00:30:05:c9:38:ff

> [Network]
> IPv6AcceptRA=yes
> DHCP=yes

> [DHCP]
> UseDomains=true
> ---

> When the clients come up, or when I restart systemd-networkd on the
> client, I see this in the dhcpd logs:

> Apr 7 15:54:19 prokyon dhcpd[9823]: Solicit message from fe80::230:5ff:fec9:38ff
> port 546, transaction ID 0xF7324300
> Apr 7 15:54:19 prokyon dhcpd[9823]: Advertise NA: address
> fd10:2842:f0d1:101:af31:9c41:dd6b:7d5 to client with duid
> 00:02:00:00:ab:11:71:bc:09:50:c1:3c:0b:51 iaid = 1232215879 static
> Apr 7 15:54:19 prokyon dhcpd[9823]: Sending Advertise to fe80::230:5ff:fec9:38ff
> port 546
> Apr 7 15:54:19 prokyon dhcpd[9811]: DHCPREQUEST for 192.168.0.21 (192.168.0.251)
> from 00:30:05:c9:38:ff via eth0
> Apr 7 15:54:19 prokyon dhcpd[9811]: DHCPACK on 192.168.0.21 to 00:30:05:c9:38:ff
> via eth0
> Apr 7 15:54:20 prokyon dhcpd[9823]: Request message from fe80::230:5ff:fec9:38ff
> port 546, transaction ID 0x8DF86200
> Apr 7 15:54:20 prokyon dhcpd[9823]: Discarding Request from
> fe80::230:5ff:fec9:38ff; not our server identifier (CLIENTID
> 00:02:00:00:ab:11:71:bc:09:50:c1:3c:0b:51, SERVERID
> 00:03:00:01:00:1d:aa:97:f0:44, server DUID
> 00:01:00:01:26:1f:32:19:02:a5:04:3d:96:27)

> The client then assigns an address to it's eth0 interface, that is completely
> wrong:

> eth0: flags=4163<UP,BROADCAST,RUNNING,MULTICAST> mtu 1500
> inet 192.168.0.21 netmask 255.255.255.0 broadcast 192.168.0.255
> inet6 fe80::230:5ff:fec9:38ff prefixlen 64 scopeid 0x20<link>
> inet6 fd10:2842:f0d1:101::1 prefixlen 128 scopeid 0x0<global>
> inet6 2001:470:52a0:101:230:5ff:fec9:38ff prefixlen 64 scopeid 0x0<global>
> ether 00:30:05:c9:38:ff txqueuelen 1000 (Ethernet)
> RX packets 14402 bytes 6624577 (6.3 MiB)
> RX errors 0 dropped 0 overruns 0 frame 0
> TX packets 9253 bytes 1639921 (1.5 MiB)
> TX errors 0 dropped 0 overruns 0 carrier 0 collisions 0
> device interrupt 17

> For explanation, the address 2001:470:52a0:101:230:5ff:fec9:38ff is the
> SLAAC address. The DHCPV6 address should be
> fd10:2842:f0d1:101:af31:9c41:dd6b:7d5 as sent by the dchp server. But
> the client assignes fd10:2842:f0d1:101::1 to its interface (the other
> client fd10:2842:f0d1:101::2), addresses that I never have configured
> anywhere.

> Other Linux clients using NetworkManager, or Windows 10 Clients, get
> configured well in that setup.

> What is going wrong here? I don't know if this is a server side or a
> client side problem.

> What I already did: Deleted all lease files in /var/lib/dhcp and
> restarted isc-dhcp-server (server side). Restarted clients. No success.

> Thanks for help,

> Robert

> --
> Robert Senger

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