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DHCPv6 clients that can request multiple prefixes (self.ipv6)

submitted 1 year ago by iwasgodonce to c/ipv6

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I'm on att for my home internet and unless you go to the effort to bypass their router (it does 802.1x authentication so it's a bit of a pain to do so), they only give you /64s via dhcpv6 prefix delegation, nothing bigger. You can request up to 8 of them though.

It looks like mikrotik can't request multiple prefixes in a single request, based on their documentation.

Edge routers look like they can if configured from the cli.

I've been using a linux box with dhcpcd and that works. Would be nicer if systemd-networkd supported multiple prefixes directly so I didn't have to try to get dhcpcd and systemd-networkd to try to play nice with each other since I use systemd-networkd for the lan side interfaces, wireguard, etc.

What other routers and dhcpv6 clients support requesting multiple prefixes in a single request? I'm looking to see if there's a better option out there than what I'm doing now.

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[–] TCB13 4 points 1 year ago (1 children)

Would be nicer if systemd-networkd supported multiple prefixes directly

I believe a fix for this was merged last year please read https://github.com/systemd/systemd/issues/22571 and https://github.com/systemd/systemd/pull/22574. Check what version it was actually released and if your Linux latest version already has it.

Another option would be to create a bridge and/or macvlan and them place multiple virtual connections on it, each one requesting and having a different IPv6 prefix.

[–] iwasgodonce 1 points 1 year ago (1 children)

It looked to me like what was merged didn't actually solve that issue.

Do you know if multiple interfaces like that would work without having to make custom source routing rules? (so the right ip addresses go out the interface associated with the dhcp range) Would connection tracking (for use with nftables) be able to work correctly without source routing rules. I'd be afraid if I had to hard code source routing rules that if the power went out for a while, it would end up with the wrong range assigned to a given interface.

[–] TCB13 2 points 1 year ago

If you've a bridge it shouldn't matter, at the end of the day everything will come out on the same place. Either way there are a few options systemd's network config under the [Route] and [RoutingPolicyRule] sections that might help you setup priorities and some kind of tracking automatically. Whenever you get new prefixed systemd will automatically recreate the routes for you.

https://www.freedesktop.org/software/systemd/man/systemd.network.html#%5BRoutingPolicyRule%5D%20Section%20Options

To be honest I'm not sure if those things will work as expected. You'll have to read the docs very carefully and try. I've had my fair share of issues with systemd and IPv6, PD, SLAAC, DAD and others in the past. Most things seem to be fixed now, but systemd wasn't designed as a networking solution like, for instance, OpenWRT is.