Это очень старая проблема. В протоколах PPP не предусмотрел перезвон клиента при корректном закрытии сессии сервером, а MPD5 очень четко следует протоколам. И попытки это исправить только создавали больше проблем. Я уже честно подзабыл что было лучшим решением. Как вариант -- настроить on-demand, и оно будет перезванивать по первому-же исходящему пакету.
I worry whether different priority for LCP packets may put them into different queue, that may cause packet reorder, IIRC generally unacceptable for PPP.
Your PPTP client is configured for MSCHAPv2 only.
Your PPTP client is configured for PAP only.
No. Unlike PAP CHAP protects communication oover the wire, but it require plain-text passwords on RADIUS server side. PAP on the other side is plain-text over the wire, but because if that it can be used with hashed passwords file.
mpd does not keep the configuration in textual form.
That is right. I have little IPv6 experience lately. IIRC there are two ways to assign IPv6 addresses -- NDP and DHCPv6. AFAIK any of those can be used with MPD, but it may be difficult to make them cooperate with MPD authentication, if you use it to control connection parameters.
I know nothing about ng_mikrotik_eoip module. PPPoE code in mpd needs ethernet node to havd orphans hook it could attach to handle PPPoE traffic. If ng_mikrotik_eoip node has it too, then it may be a question of only adding respective node name into mpd. Otherwise it may be difficult.