Adam21h ago
I'm getting into the IPv6 weeds and I need some help. Can someone explain what the Announce parameter does under [DHCPPrefixDelegation] in systemd-networkd?
I feel like it should mean to announce available /64s out of the /56 received from the ISP so internal routers could use them for their own networks. If it does mean that, I have no idea how to make it work.
I'm just an enthusiast trying to learn, but if anyone could help me out I'd appreciate it.
#selfhosting #linux #networking #ipv6
Show threadMorgan21h ago

@adaroc here's the docs, seems to me this would readvertise the delegated block entirely for a downstream device instead of using one of the subnets for the interface.

> Announce= Takes a boolean. When enabled, and IPv6SendRA= in [Network] section is enabled, the delegated prefixes are distributed through the IPv6 Router Advertisement. This setting will be ignored when the DHCPPrefixDelegation= setting is enabled on the upstream interface. Defaults to yes. Added in version 247.

Show threadMorgan21h ago

@adaroc I'd think of you're using this as your router and having multiple vlans on it you wouldn't want to advertise but instead use DHCPPrefixDelegation=true and IPv6SendRA=true.

If you're trying to delegate your prefix to another router that's where I'd assume Announce would be used.

Show threadAdam21h ago
@cereal_cable that is what I'm trying to do. On the router connected to the ISP delegation works fine. I have another downstream router and I thought it would be nice to give it another /64 for it to use. Can't seem to make it go.
Show threadMorgan21h ago
@adaroc I'd think you could do all delegated or none. I'd be surprised if you could mix / match without doing something more router centric.
Show threadAdam21h ago
@cereal_cable you're probably right. It looks like I'd have to run DHCP6 on the main router to do what I want. I can also just "cheat" and manually assign a /64 out of the /56 to the internal router, which I probably won't regret doing until my ISP changes my prefix...
Show threadMorgan21h ago
@adaroc its definitely less work to "cheat" especially if you're attempting to only send a slice over. Maybe one day it'll be more of an option.
Show threadAdam
@cereal_cable that's definitely true. I probably should make an ansible play book to run when my prefix changes, which is just rare enough that it's hard to remember all the stuff I have to change. 😀
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Show threadMorgan14h ago
@adaroc probably could just have a DHCP hook trigger a script to start it all.