seeking advice from #linux/#networking folk

I have a ppp over l2tp interface, using xl2tpd and pppd. The L2TP bit seems to work OK, the PPP interface comes up and negotiates IPv4 addresses then IPV6 link addresses.

I can v4 ping both ends of the connection But: I can't ping the v6 link addresses (maybe this is normal) and when I run odhcp6c to get a prefix delegation, it sends a SOLICIT but doesn't see the ADVERTISE replies from the DHCP6 server

(I know the DHCP6 server is sending replies because I can see them in tcpdump)

  • The kernel doesn't have netfilter or any iptables stuff compiled in, so I don't think there's any kind of firewalling

  • rp_filter, as far as I can tell, works only for ipv4 not ipv6

I'm a bit stuck for what to try next. Any ideas?

self reply

OK, this remains weird but I appear to have a workaround. Run

ip addr del fe80::dead:beef scope link dev ppp0

then

ip addr add fe80::dead:beef scope link dev ppp0

(where ipv6 ::dead:beef is passed as a ppp option)

and now it works. Something in the way that pppd configures that address is wrong, I guess