Hi again, On Thu, Feb 19, 2009 at 2:53 AM, richardvo...@gmail.com <richardvo...@gmail.com> wrote: > Please keep replies on the list. > > On Wed, Feb 18, 2009 at 10:15 AM, Chris Green <ch...@isbd.co.uk> wrote: >> On Wed, Feb 18, 2009 at 01:50:08AM +0000, richardvo...@gmail.com wrote: >> [snip] >>> > >>> > No other configuration files needed -- on any host -- just let >>> > everybody use dhcp. Super easy. But will this work? >>> >>> No. dnsmasq determines which dhcp-range to use when giving out >>> addresses from the IP address configured on the interface where the >>> DHCP-REQUEST packet is received (or the interface address passed along >>> by a dhcp-relay agent). As you can see this cannot possibly work to >>> assign addresses to the dnsmasq box. There's no way around this >>> because in general dnsmasq runs on your gateway which by definition >>> has multiple interfaces. >>> >> While I'm not sure about having a 'server' assign an IP to itself it's >> surely not true that "in general dnsmasq runs on your gateway which by >> definition has multiple interfaces" - in fact it's very often *not* >> true. > > I didn't say running on the gateway was an absolute necessity, I said > it's the general (i.e. usual, common) case. Actually it is probably > only the common case for configurations using dnsmasq for DHCP. > > I'd venture to guess that multiple dhcp-ranges (including dhcp-relay) > is actually more common that your scenario. > >> >> My situation is fairly typical I would have thought:- >> >> 192.168.1.1 - Draytek Vigor 2820n router, statically assigned IP >> 192.168.1.4 - Linux 'server' running dnsmasq, currently static >> 192.168.1.xxx - other systems/devices, DHCP from 192.16.1.4 >> >> The system running dnsmasq (192.168.1.4) has only one interface, on >> the local subnet, default route is set to 192.168.1.1 and it's *that* >> which has the multiple interfaces (two more going to the outside world >> in my case). >> >> Surely this is pretty common, a proprietary router which doesn't do >> DHCP as one wants it to, so put dnsmasq on an always on Linux box on >> the local LAN. > > I think more people use the "always on Linux box" as the router in > that scenario, since if you want better DHCP than comes in the router > you probably also want netfilter instead of what firewall comes in the > router. > >> >> >> In my case it's certainly true that there are "No other configuration >> files needed", I just have /etc/hosts on 192.168.1.4 with the static >> addresses in it, /etc/resolv.conf with:- >> >> nameserver 127.0.0.1 >> nameserver 195.74.113.58 >> nameserver 195.74.113.62 >> >> ... and a pretty straightforward dsnmasq.conf file. > > Yes and now you have the additional problems of how to get dnsmasq to > know its own host needs an address (broadcast packets usually aren't > delivered to processes on the sender). Assigning the address directly > via the kernel interfaces isn't feasible because (a) dnsmasq runs on > many different OSes (b) dnsmasq drops root privilege that would be > necessary to make an address assignment and (b2) interfaces can come > up and down as media events are processed, tunnels are created, etc. >
Is what you are talking about here a setup where the host running dnsmasq would be a dhcp-client to itself? In that case, I think I may be at fault for any confusion here. To my knowledge, Chris G never said he does that -- it was just how I twisted this thread. > In addition, allowing the IP address of the DHCP server to change is > extremely bad because it breaks the renewal process. > > At some point Simon, the author, is going to wade into this discussion > with about a dozen more reasons I haven't thought of. > Ok, I think it clear to us all now that it's a bad bad idea to do that, thanks a lot, Richard! Best regards Hugo Heden