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Status: Reported (1)

RFC 3927, "Dynamic Configuration of IPv4 Link-Local Addresses", May 2005

Source of RFC: zeroconf (int)

Errata ID: 6293
Status: Reported
Type: Technical
Publication Format(s) : TEXT

Reported By: Markus Hofmann
Date Reported: 2020-09-22

Section 7 says:

7.  Router Considerations

   A router MUST NOT forward a packet with an IPv4 Link-Local source or
   destination address, irrespective of the router's default route
   configuration or routes obtained from dynamic routing protocols.

   A router which receives a packet with an IPv4 Link-Local source or
   destination address MUST NOT forward the packet.  This prevents
   forwarding of packets back onto the network segment from which they
   originated, or to any other segment.

It should say:

7.  Router Considerations

   A router MUST NOT forward a packet with an IPv4 Link-Local 
   destination address, irrespective of the router's default route
   configuration or routes obtained from dynamic routing protocols.

   A router which receives a packet with an IPv4 Link-Local 
   destination address MUST NOT forward the packet.  This prevents
   forwarding of packets back onto the network segment from which they
   originated, or to any other segment.

   A router MAY forward a packet with an IPv4 Link-Local source address if 
   the packet is an ICMP unreachable or ICMP time exceeded and the
   destination address is not a link local address.

Notes:

Link-Local IPv4 addressing is these days also often used for router to router link local connections.
Although the scope of the document is related to dynamic configuration of link local it makes statements not to forward packets for routers (not on the link local segment).
Once 169.254 addresses are used on router to router link local interfaces they might send back icmp unreachables for pmtu discovery or ttl expiration. In those cases the source IP might be a 169.254 of the routers link local router to router interface.

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