KEA and 24.1.4 and static routes options

[RedVortex]

This is not a bug or problem, this is basically just a FYI...

Careful, I made the mistake of thinking that this 24.1.4 release note was DHCP option 121 to send static routes to dhcp clients (I need this option before moving to kea) but it is not.

Code: [Select]

o kea-dhcp: add domain-search, time-servers and static-routes client options to subnet configuration

It's DHCP option 33, which is a single IP to a router IP. You cannot use this to route 192.168.30.0/24 to 192.168.31.1 for instance. You can only route 1 ip to a router, like 192.168.30.12 to 192.168.31.1 for instance.

This is basic and can still serve some purpose for some people but most of us use DHCP option 121 in ISC which is totally different than the less used DHCP option 33 which basically enforce /32 on your static route because you cannot define a subnet/CIDR on the IP/network you pass.

In other words, what we likely want, is the support for this KEA feature in OPNSense (DHCP option 121) which encompass and overrides when it is present (per RFC) option 33. Option 121 also enables you to do exactly the same as option 33 since you can specify /32 on a subnet if you want but the important part is that it allows you to specify subnets, not only individual IP addresses to be routed to a router.

https://gitlab.isc.org/isc-projects/kea/-/merge_requests/2135/diffs

Now, since this has been implemented like that. This will likely create a breaking change when option 121 is implemented unless the upgrade process converts what was specified as ip,router to ip/32,router so that we can keep the same field for the better DHCP option 121 without breaking the kea config for people that started using it already in the option 33 format. Unless someone decides to support both options in the UI and configs and then we would have 2 separate fields for static routes in the kea UI. One for single IPs (DHCP option 33) and another one for networks (DHCP option 121)

I'm very glad that a lot of work is being done on KEA and I'm almost to the point of being able to move away from ISC. Once Option 121 is implemented in OPNSense and that KEA also registers its DHCP leases hosts in Unbound, I'll be good to migrate.

Thanks everyone !

[AdSchellevis]

looking briefly at the upstream PR, I don't expect a migration challenge at a first glance, maybe a constraint that you can't send both if that's the case.

This just seems to add classless-static-route as an option (https://kea.readthedocs.io/en/latest/arm/dhcp4-srv.html), static-routes isn't removed, it's just less common to use it seems.

When this option is supported (I haven't checked version numbers) and you need it, you can always open a ticket on Github (https://github.com/opnsense/core/issues/new?assignees=&labels=&projects=&template=feature_request.md&title=)

Best regards,

Ad