The current dhcpv6 agent implementation cannot delegate agent operations to the `pppoe` interface prefix, such as the following directives:
```
listen-interface br1.2 {
address FF02::1:2
}
max-hop-count 10
upstream-interface pppoe0 {
address FF02::1:2
}
use-interface-id-option
```
The expected behavior of the configuration is that the subordinate devices of `br1.2` are expected to delegate requests to `pppoe` via the dhcpv6 prefix in order to complete the prefix delegate, but the actual situation is:
```
vyos@vyos# sudo /usr/sbin/dhcrelay -6 -pf /run/dhcp-relay/dhcrelay6.pid -l FF02::1:2%br1.2 -u FF02::1:2%pppoe0 -c 10 -I
Internet Systems Consortium DHCP Relay Agent 4.4.1
Copyright 2004-2018 Internet Systems Consortium.
All rights reserved.
For info, please visit https://www.isc.org/software/dhcp/
Bound to *:547
Listening on Socket/br1
Sending on Socket/br1
Listening on Socket/eth5
Sending on Socket/eth5
Listening on Socket/eth4
Sending on Socket/eth4
Listening on Socket/eth3
Sending on Socket/eth3
Listening on Socket/eth2
Sending on Socket/eth2
Listening on Socket/eth1
Sending on Socket/eth1
Listening on Socket/eth0
Sending on Socket/eth0
Unsupported device type 512 for "pppoe0"
If you think you have received this message due to a bug rather
than a configuration issue please read the section on submitting
bugs on either our web page at www.isc.org or in the README file
before submitting a bug. These pages explain the proper
process and the information we find helpful for debugging.
exiting.
```
Is it possible to consider using Kea DHCPv6 instead of ISC DHCPv6, or a better solution?