On 21/09/2020 21:32, Paul Gear wrote: > Hi all, > > I've been trying to solve the same problem described in this blog post: > https://blog.fhrnet.eu/2020/03/07/dhcp-server-on-a-32-subnet/ > > In a nutshell, the situation is a VM host which performs routing and > firewalling for all its guests, providing an isolated IPv4 /32 (and in > my case an IPv6 /64 or /128 as well) to each VM guest, and using > interface routes on the host to direct traffic to each guest, without > wasting IPv4 addresses on /31 or /30 point-to-point links. > > The post claims that the configuration noted (a single /32 allocated to > the host which is configured on every client-facing interface) is only > possible at present with ISC DHCP. I've tested a number of different > configurations of dnsmasq, and this seems to be correct. I'm hoping > someone experienced in the dnsmasq code base can confirm or deny this. > > Assuming this is currently a limitation, I'd like to work on adding > support to dnsmasq for this scenario. I'm not experienced with the code > base (although I've read some of the relevant portions and believe it > should be possible), so I'm hoping also for some guidance on whether > this functionality would be accepted into the code base, and if so, how > it might appear in the configuration. > > My initial thought was that there wouldn't need to be any explicit > configuration; rather, if a DHCP request is received on an interface > with a /32 mask (or perhaps on an interface with a non-unique address on > the host), the usual restrictions around interface matching would be > relaxed, and an address would be given out either from the > statically-defined hosts, or from a pool which doesn't match any > interface on the host. When giving out IPv6 addresses, my thought was > that things would mostly work the same if a DHCPv6 request was received > on an interface with only link-local addressing configured.
This sounds like the use case for shared-network: shared-network=virbr13,192.168.1.26 or shared-network=172.16.0.1,192.168.1.26 Alternatively, i sent this patch a while ago to be able to ignore any matching, but my use case is different. I can send an updated version if people are interested. http://lists.thekelleys.org.uk/pipermail/dnsmasq-discuss/2018q1/012070.html _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
