pfSense

On a PPPoE connection with if_pppoe and VIPs (tested with IPv4), interrupting the server side (e.g. by restarting the server) results in a link up/down loop.

Oct 14 22:35:22     php     55063   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface igb0
Oct 14 22:35:22     php     55063   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface pppoe0
Oct 14 22:35:22     php     55063   /usr/local/sbin/ppp-ipv6: Starting rtsold process on opt1(pppoe0)
Oct 14 22:35:22     php     57674   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface igb0
Oct 14 22:35:23     php     57674   /usr/local/sbin/ppp-ipv6: Starting DHCP6 client for interfaces igb0
Oct 14 22:35:24     rtsold  62006   <interface_up> pppoe0 does not accept Router Advertisement.
Oct 14 22:35:31     kernel      in_scrubprefix: err=65, prefix delete failed
Oct 14 22:35:31     kernel      pppoe0: link state changed to UP
Oct 14 22:35:31     kernel      pppoe0: link state changed to DOWN
Oct 14 22:35:31     kernel      if_pppoe: pppoe: GENERIC ERROR (errortag 1)
Oct 14 22:35:32     php     11065   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface igb0
Oct 14 22:35:32     php     11065   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface pppoe0
Oct 14 22:35:32     php     12821   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface igb0
Oct 14 22:35:32     php     12821   /usr/local/sbin/ppp-ipv6: Starting DHCP6 client for interfaces igb0
Oct 14 22:35:34     php     11065   /usr/local/sbin/ppp-ipv6: Starting DHCP6 client for interfaces igb0,pppoe0
Oct 14 22:35:34     php     11065   /usr/local/sbin/ppp-ipv6: Starting rtsold process on opt1(pppoe0)
Oct 14 22:35:36     rtsold  19594   <interface_up> pppoe0 does not accept Router Advertisement.
Oct 14 22:35:41     kernel      in_scrubprefix: err=65, prefix delete failed
Oct 14 22:35:42     kernel      pppoe0: link state changed to UP
Oct 14 22:35:42     kernel      pppoe0: link state changed to DOWN
Oct 14 22:35:42     kernel      if_pppoe: pppoe: GENERIC ERROR (errortag 1)
Oct 14 22:35:43     php     26756   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface igb0
Oct 14 22:35:43     php     26756   /usr/local/sbin/ppp-ipv6: Accept router advertisements on interface pppoe0
Oct 14 22:35:43     php     26756   /usr/local/sbin/ppp-ipv6: Starting rtsold process on opt1(pppoe0)

Reportedly, downing the interface with ifconfig without deleting the VIPs can result in similar behavior. Further discussion on the forum:
https://forum.netgate.com/topic/198027