Turns out, you have to explicitly add a link local address *after* the interface is in an up state! Only then the multicast route is installed. This is unexpected, since a random link local is already assigned and veth-interfaces behave fully as expected (multicast is enabled right after the interface is brought up). The inconsistent behaviour between interface types and OS versions makes it seem like a bug. #tunnel #gre #ip6gre #followerpower #network #debian

A comparison of two fresh installations of Debian 11 (Kernel 5.10) and 12 (Kernel 6.1) reveals significant differences in behaviour. While Debian 11 creates both an anycast and a multicast route in the local routing table, Debian 12 creates neither.
So, how do I get back the Debian 11 behaviour on 12?
#tunnel #gre #ip6gre #followerpower #network #debian

Networking question: (Debian 12)
Setting up ´ip netns´, moving #ip6gre #tunnel inside netns and enabling multicast via ´ip netns exec {netns} ip link set {tun-name} multicast on´, upping interface.
Since upgrade to Debian 12 no multicast ping is possible afterwards. Routing table `local` has no multicast entry. After manually adding a multicast route, multicast ping is possible.
What changed between Debian 11 and 12? What do I need to do to enable multicast ping directly? #followerpower #network