The Quagga version in Debian 8 (v0.99.23.1) suffers from a bug in ospf6d, which causes that no IPv6 routes are exchanged via point-to-point interfaces.
In order to workaround this problem (and re-establish IPv6 connectivity), a downgrade of the quagga package can be done.
For this we add the 'oldstable' entry to sources.list and pin the quagga package to the old version.
Entry to add to /etc/apt/sources.list:
deb http://mirror.switch.ch/ftp/mirror/debian/ oldstable main
Entry to add to /etc/apt/preferences:
Pin: version 0.99.22.*
After the entries have been added, run apt-get update followed by apt-get install quagga to downgrade to the old quagga package.