On 1/30/17 8:49 AM, Roopa Prabhu wrote: >> Single next hop delete will be around because IPv6 allows it -- and because >> IPv4 needs to support it. >> > understand single next hop delete for ipv6 will be around..and my only point > was to leave it around but not optimize for that case. > I don't think we should support single nexthop delete in ipv4 (I have not > seen a requirement for that)... ipv4 is good as it is right now. > the additional complexity is not needed. >
IPv4 has a known bug -- delete a virtual interface in a multihop route and the entire route is deleted, including the nexthops for other devices. This does not happen for IPv6. Simple example of that bug: ip li add dummy1 type dummy ip li add dummy2 type dummy ip addr add dev dummy1 10.11.1.1/28 ip li set dummy1 up ip addr add dev dummy2 10.11.2.1/28 ip li set dummy2 up ip ro add 1.1.1.0/24 nexthop via 10.11.1.2 nexthop via 10.11.2.2 ip li del dummy2 --> the entire multipath route has been deleted. And, fixing this bug enables work to make IPv4 append to be sane -- appending a route should modify an existing route by adding the nexthop, not adding a new route that I believe can never actually be hit. Both cases mean modifying an IPv4 route -- adding or removing nexthops -- a capability that IPv6 allows so fixing this means closing another difference between the stacks.
