!tCyGickeVqkHsYjWnh:nixos.org

NixOS Networking

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Declaratively manage your switching, routing, wireless, tunneling and more. | Don't rely on `networking.*` for interface and routing setup, use systemd-networkd, ifstate or NetworkManager instead. | Set `SYSTEMD_LOG_LEVEL=debug` to debug networking issues with networkd | No bad nft puns, please. | Room recommendations: #sysops:nixos.org253 Servers

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SenderMessageTime
2 Jun 2025
@hexa:lossy.networkhexa (clat on linux when)or enabled forward in sysctl00:28:49
@hexa:lossy.networkhexa (clat on linux when)https://www.freedesktop.org/software/systemd/man/latest/systemd.network.html#IPv6Forwarding=00:29:06
@charles:computer.surgeryCharlesi assumed that that isn't necessary for ipv6 for some reason00:29:11
@hexa:lossy.networkhexa (clat on linux when)

Defaults to true if IPMasquerade= is enabled for IPv6 or IPv6SendRA= is enabled

00:29:25
@hexa:lossy.networkhexa (clat on linux when)so should be enabled on br-lan00:29:35
@hexa:lossy.networkhexa (clat on linux when)but maybe not on wan00:29:44
@hexa:lossy.networkhexa (clat on linux when)i tend to yolo this part00:30:24
@hexa:lossy.networkhexa (clat on linux when)
  boot.kernel.sysctl = {
    "net.ipv6.conf.all.forwarding" = lib.mkForce 1;
    "net.ipv4.forward" = lib.mkForce 1;
  };
00:30:28
@saiko:knifepoint.net@saiko:knifepoint.netsystemd.network.config.networkConfig.IPv6Forwarding = true;00:31:26
@charles:computer.surgeryCharles hmm i have boot.kernel.sysctl."net.ipv4.ip_forward" = "1"; lol 00:31:52
@hexa:lossy.networkhexa (clat on linux when)yeah, that would be the systemd-networkd equivalent00:31:59
@hexa:lossy.networkhexa (clat on linux when)yeah, so feel free to grab the ipv6 one as well00:32:10
@hexa:lossy.networkhexa (clat on linux when)or use the networkd knob00:32:14
@charles:computer.surgeryCharlesi feel like in the past when i try doing it the systemd-networkd way it doesn't work and you need both or something00:32:34
@charles:computer.surgeryCharlesdo i need to reboot for that00:33:17
@hexa:lossy.networkhexa (clat on linux when)I don't think so00:34:20
@hexa:lossy.networkhexa (clat on linux when)sysctl's can be set at runtime00:34:29
@charles:computer.surgeryCharles
PING 2600:: (2600::) 56 data bytes
From 2601:1c1:8400:a440:10b8:f6ff:fef0:f963 icmp_seq=1 Destination unreachable: No route
00:34:47
@hexa:lossy.networkhexa (clat on linux when)try something else, just to be safe 😄 00:35:23
@hexa:lossy.networkhexa (clat on linux when)

Destination unreachable: No route

00:35:44
@saiko:knifepoint.net@saiko:knifepoint.net
In reply to @charles:computer.surgery
i feel like in the past when i try doing it the systemd-networkd way it doesn't work and you need both or something
there are two, you need the global option, not the one on the netdev, at least for IPv6
00:35:49
@hexa:lossy.networkhexa (clat on linux when)given that you have a default route on your router00:35:57
@elvishjerricco:matrix.orgElvishJerriccoIIRC ipv6 forwarding is weirder than ipv4 forwarding and you have to have both the per-interface and global settings enabled or something00:36:01
@saiko:knifepoint.net@saiko:knifepoint.net(same as you need to turn on conf.all.forwarding and not the interface one, or at least both)00:36:13
@saiko:knifepoint.net@saiko:knifepoint.netyeah00:36:17
@hexa:lossy.networkhexa (clat on linux when)the reason why I just don't bother with networkd for forwarding options00:36:21
@saiko:knifepoint.net@saiko:knifepoint.netthe global one turns all the interface ones on00:36:27
@saiko:knifepoint.net@saiko:knifepoint.netno, this is a kernel level thing, not networkd00:36:33
@hexa:lossy.networkhexa (clat on linux when)fair00:36:44
@elvishjerricco:matrix.orgElvishJerricco

Note, unlike IPv4Forwarding=, enabling per-interface IPv6Forwarding= on two or more interfaces DOES NOT make IPv6 packets forwarded within the interfaces. This setting just controls the per-interface sysctl value, and the sysctl value is not directly correlated to whether packets are forwarded. To ensure IPv6 packets forwarded, the global setting in networkd.conf(5) needs to be enabled.

00:36:58

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