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This bug was initially created as a copy of Bug #2079808


Add support for IPv4 multihop (multipath, ECMP) routes.

Currently NetworkManager ignores all IPv4 multihop routes and cannot configure them. This should be fixed.


For IPv6, kernel will automatically merge compatible single-hop routes (that only differ by their next hop). So NetworkManager supports multihop routes by just pretending there are only multi-hop routes. If you configure two routes that only differ by their next-hop, then NM will configure them, kernel will treat them as multi-hop and all works. The only thing that is missing for IPv6 is to configure a weight for the next hop.

For IPv4, it's entirely different. The next hop (or hops) of an IPv4 route is part of the identity of an IPv4 route, that means, if you have two routes that only differ by their next hop(s), then these are just two different routes as far as kernel is concerned.

Seems to work fine here (except for the off-by-one weight that will be addressed in a later patch):

  # nmcli connection add type dummy ifname dummy1 ip4 172.25.10.1/24 ipv4.routes "192.168.1.1 10 weight=100"
  Connection 'dummy-dummy1' (dcc4e533-cea4-4d70-a48f-3edd6c0686a7) successfully added.

  # nmcli connection add type dummy ifname dummy2 ip4 172.25.10.2/24 ipv4.routes "192.168.1.1 10 weight=200"
  Connection 'dummy-dummy2' (490fb23f-ed9a-42f2-82e1-6f9e41eadd1b) successfully added.

  # ip route
  [...]
  192.168.1.1 proto static scope link metric 10
	nexthop dev dummy1 weight 101
	nexthop dev dummy2 weight 201

Setting Verified:Tested.

VERIFIED using NetworkManager-1.41.90-1.el9.x86_64

The functionality works, automation coverage may be augmented in the future.

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory (NetworkManager bug fix and enhancement update), and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHBA-2023:2485