Occasional warnings in ipv6 logs


  • I have noticed occasionally in the wan_dhcp6 renewal process I am seeing logged kernel errors (warnings) reporting it cannot foward src.

    examples below

    Jan 13 22:39:15	kernel		cannot forward src fe80:4::c6e9:84ff:x:x, dst x0:1450:4009:80e::200e, nxt 6, rcvif igb1, outif igb0
    Jan 13 22:41:25	kernel		cannot forward src fe80:4::c6e9:84ff:x:x, dst x0:1450:4009:80e::200e, nxt 6, rcvif igb1, outif igb0
    Jan 13 22:42:18	kernel		cannot forward src fe80:4::c6e9:84ff:x:x, dst x1:578:3::34d1:3bdc, nxt 6, rcvif igb1, outif igb0
    Jan 13 22:43:36	kernel		cannot forward src fe80:4::c6e9:84ff:x:x, dst x0:1450:4009:80d::200a, nxt 6, rcvif igb1, outif igb0
    

    I censored some octets, the dst octets are very close to my actual wan ip prefix but not quite in the same range.

    From what I can observe there is no actual ipv6 outages as the connection is monitored and I have idle ssh sessions which are remaining connected, so just curious on thoughts on what I am seeing.  If there is a way to silence it and if it represents a real problem.

  • Rebel Alliance Developer Netgate

    Something tried to send traffic sourced from a link-local address to a destination off the local network, which is illegal so it dropped the packet. Find whatever is bound to that fe80 address.


  • You've probably either figured this out already or just decided to ignore it but I have found that those errors are typically caused by an IPv6 client that doesn't support DHCPv6 and your IPv6 Router Advertisements are configured not to support SLAAC (set to either "Managed" or "Disabled" on that interface).

    Under "Services/DHCPv6 Server & RA", change your RA mode to "Assisted" or "Stateless" on the interface those clients are connected to and this error should disappear.