[Kea-users] DHCPv6, shared network, and double-relay Solicit messages

[mxhajduczenia at gmail.com]

Dear colleagues, 

 

I have been attempting to test a setup in the lab with DOCSIS CM operating
in IPv6 mode only, where the DHCPv6 messages are relayed across the CMTS and
the first-hop router (relay address 2600:6ce4:0:3e::1) towards a Kea server
running 2.4 code (address 2600:6ce4:0:42::130). 

 

At the Kea server level, I ran a packet capture, to observe an interesting
behavior - the Solicit messages from the DOCSIS CM are being forwarded back
to the relay, embedded within the ICMPv6 message with indication that the
destination is unreachable for some reason. 

 



 

The Kea server is running without any issues so it seems that the binding is
successful and 

 

root at server-kea-node1:/home/ace# service isc-kea-dhcp6-server status


● isc-kea-dhcp6-server.service - Kea DHCPv6 Service

     Loaded: loaded (/lib/systemd/system/isc-kea-dhcp6-server.service;
enabled; vendor preset: enabled)

     Active: active (running) since Tue 2024-04-23 15:02:41 UTC; 11min ago

       Docs: man:kea-dhcp6(8)

   Main PID: 1551 (kea-dhcp6)

      Tasks: 7 (limit: 4550)

     Memory: 3.5M

        CPU: 119ms

     CGroup: /system.slice/isc-kea-dhcp6-server.service

             └─1551 /usr/sbin/kea-dhcp6 -c /etc/kea/kea-dhcp6.conf

 

Apr 23 15:14:29 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:29.467
DEBUG [kea-dhcp6.commands/1551.140682475032192]
COMMAND_SOCKET_CONNECTION_OPENED Opened socket 22 for incoming command
connection

Apr 23 15:14:29 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:29.468
DEBUG [kea-dhcp6.commands/1551.140682475032192] COMMAND_SOCKET_READ Received
129 bytes over command socket 22

Apr 23 15:14:29 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:29.468
INFO  [kea-dhcp6.commands/1551.140682475032192] COMMAND_RECEIVED Received
command 'statistic-get'

Apr 23 15:14:29 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:29.468
DEBUG [kea-dhcp6.commands/1551.140682475032192] COMMAND_SOCKET_WRITE Sent
response of 92 bytes (0 bytes left to send) over command socket 22

Apr 23 15:14:29 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:29.468
DEBUG [kea-dhcp6.commands/1551.140682475032192]
COMMAND_SOCKET_CONNECTION_CLOSED Closed socket 22 for existing command
connection

Apr 23 15:14:30 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:30.158
DEBUG [kea-dhcp6.commands/1551.140682475032192]
COMMAND_SOCKET_CONNECTION_OPENED Opened socket 22 for incoming command
connection

Apr 23 15:14:30 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:30.158
DEBUG [kea-dhcp6.commands/1551.140682475032192] COMMAND_SOCKET_READ Received
117 bytes over command socket 22

Apr 23 15:14:30 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:30.158
INFO  [kea-dhcp6.commands/1551.140682475032192] COMMAND_RECEIVED Received
command 'statistic-get-all'

Apr 23 15:14:30 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:30.158
DEBUG [kea-dhcp6.commands/1551.140682475032192] COMMAND_SOCKET_WRITE Sent
response of 8715 bytes (0 bytes left to send) over command socket 22

Apr 23 15:14:30 server-kea-node1 kea-dhcp6[1551]: 2024-04-23 15:14:30.158
DEBUG [kea-dhcp6.commands/1551.140682475032192]
COMMAND_SOCKET_CONNECTION_CLOSED Closed socket 22 for existing command
connection

 

I attach the Kea DHCPv6 config for reference (keav6.json) - the test device
should match rpd-10 class, and make its way into 2600:6ce4:0:3e::/64 subnet.


 

I am drawing blank on what the problem might be in here. I have not seen
this behavior before and I am not sure whether it is related with the fact
that I have two layers of relays in messages or not

 

Regards

 

Marek

 

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