The DHCPv6 relay sends an oddly formatted Interface-ID

[Gorf]

Hi all, I'm having a hard time getting the DHCPv6 Relay working correctly with my Kea 2.6 dhcp server. The relay definitely sends the forwarded request because I can see it in tcpdump on my dhcp server:

root@dhcp1:/etc/kea# tcpdump -i ens18 -n -vv '(udp port 546 or 547)'
tcpdump: listening on ens18, link-type EN10MB (Ethernet), snapshot length 262144 bytes

20:58:44.466928 IP6 (hlim 64, next-header UDP (17) payload length: 133) 2603:3023:62c:e160::1.547 > 2603:3023:62c:e160::11.547: [udp sum ok] dhcp6 relay-fwd (linkaddr=2603:3023:62c:e101::1 peeraddr=fe80::14fb:97ff:fe88:25a7 (interface-ID 04000000...) (relay-message (dhcp6 solicit (xid=f8aad (elapsed-time 0) (client-ID hwaddr type 1 16fb978825a7) (IA_PD IAID:0 T1:0 T2:0 (IA_PD-prefix ::/64 pltime:0 vltime:0)) (option-request opt_82) (rapid-commit))))

However, you can see that what PFSense is sending across, while it has the correctly formatted linkaddr, the interface-ID is "04000000..." and that doesn't make any sense to me. Has anyone seen this before? It's not a valid hex value (meaning it doesn't convert to ascii as anything meaningful), and I don't understand the trailing periods.

[gigabitguru]

@Gorf Grab it from tcpdump or wireshark. It's truncated in the log. Should look something like this: