-----BEGIN PGP SIGNED MESSAGE----- Hash: SHA256 Hi Vikram,
Dnsmasq imposes a hard limit on the number of DHCP leases, to avoid DoS attacks. Old releases used to default this to 150, I think. Current releases have the default at 1000. The limit can be changed with the dhcp-lease-max config parameter. The practical maximum number of leases before things break is not well characterised. I suspect that there are some loops which are O(n^2) on the number of leases, so that will eventually eat too much CPU, but only at very large values of n. Probably what will get you first is the iops to write the lease file. That gets (re-)written, all of it, whenever any lease is created, renewed, or destroyed. It's also synced to real disk each time, so the writes have to make it to the spinning rust. Eventually you'll be using too much disk bandwidth. Of course that can be worked around keeping it on a RAM disk or SSD or not using a lease file (either because you don't care about persisting leases, or you're using an external database engine, which would be much more efficient). I be surprised to see problems with less than 10000 leases on enterprise hardware (fast CPU, plenty of memory, fast disks). The DNS aspect shouldn't be a problem: as far as the DNS subsystem is concerned, a DHCP lease is equivalent to a DNS cache entry, and that easily scales to hundred of thousands. Do you have any numbers on what works? Cheers, Simon. On 11/12/14 22:49, Vikram Hosakote (vhosakot) wrote: > Hi Simon, > > This is Vikram at Cisco Systems. I have recently been scaling DHCP > with dnsmasq. > > I see this scale info in the manual page of dnsmasq (man dnsmasq) > under the LIMITS section. > > Dnsmasq is capable of handling DNS and DHCP for at least a > thousand clients. > > Is there an upper limit for the maximum number of DHCP clients > dnsmasq can handle with and without DNS ? > > Thanks a lot! > > Regards, Vikram Hosakote OpenStack Software Engineer | > vhosa...@cisco.com Cloud and Virtualization Group | Cisco > Systems Boxborough MA | Work : > 978-936-8799 > -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCAAGBQJUiiN3AAoJEBXN2mrhkTWiCHwP/318wMcuF8QxAMvfIUbkXtxP j2H2ynK6gC0JY+X9OMDzAB6MNG6e2lAs7MCfpO+buyanK2rY2vZfFwgwVeEJNiUO d7jeJoGAuAYYWMG7Jz3hG2yUmMUqBGlUU8cPMHEdRhh1G+SM9/Foz96I82fY/m71 Iec+LjPwvM77Vz5gtbmVev6P12bBAgBAvvFqNLbE8Zpz91kIoRa7nKTVA/lJjEt9 0nEbv3zwv6QHZdhHcw+wkgddFoxmJlEat055GQSp8D2hXJ21Kbr6I7f0f7OkSe8P WF662ne8RYGSoIDWB75Qsw5uWf5MA0JIth3sG/I57WA5CtGa6k0an7Qlq+4UZkBJ FSBoar42KNo95/Fj90BP+PPZRfx7NnBQCnto0dzmT1AaJLV9QBuQq4l/OrcTIUGZ WUO41QB/873uKHLHruLfbtXsy874o1HJ8/Sl7QPdJlVwTLzSl7IYqdO2cCwpn27W bs4w3e3wOFRFNy72VKc84vr6KKuOCuiqCy3X+hpgZsG40Y/IFccorUkqZL5953sA djjV7urNhQP7+6XoEJayIRsCfpA8YuNl9CTZAnyKLYPnAwG5EBYmW/KgaqtCV78O i/MxMzjB7j2cAkA1dvSyZ7+IGYe/xae9HS9BJPvxzC7a8kQvrs7we2l/QVNsyAGm j7RqQL4fgImsPNjPCxWn =HuNh -----END PGP SIGNATURE----- _______________________________________________ Dnsmasq-discuss mailing list Dnsmasq-discuss@lists.thekelleys.org.uk http://lists.thekelleys.org.uk/mailman/listinfo/dnsmasq-discuss
