Am Fri, 31 Oct 2014 07:09:08 -0400 schrieb Rich Freeman <ri...@gentoo.org>:
> On Fri, Oct 31, 2014 at 6:47 AM, Marc Joliet <mar...@gmx.de> wrote: > > Am Fri, 31 Oct 2014 07:52:54 +0100 > > schrieb "J. Roeleveld" <jo...@antarean.org>: > >> On Tuesday, October 28, 2014 07:31:56 PM Marc Joliet wrote: > >> > > >> > - I don't know whether we have an IP block or not; I suspect not. At the > >> > very least, we didn't make special arrangements to try and get one. > >> > >> Then assume not. Most, if not all, ISPs charge extra for this. (If they > >> even > >> offer it) > > > > That's what I thought :) . > > > > Generally speaking you can't just attach a modem to your LAN and have > it act as a DHCP server. Your ISP probably will assign you dynamic > IPs, but they will not as a matter of policy assign you more than one > unless you pay for them. IPv4 address space is in short supply these > days. > > I'm using FIOS and in my case the "modem" is in a box in the basement > and the ISP provides a router with the service. Whatever you plug > into the "modem" will obtain a DHCP lease for one routable IP. If you > do plug more than one device into the "modem" then the first device to > get the IP is the only one that will get an IP - the modem won't hand > out another unless it gets a DHCPRelease from the MAC that was issued > the original lease or until that lease expires, or until you call up > the ISP on the phone and get them to release it manually. > > Another design would be to issue a new IP anytime a device asks for > one, but to silently cancel the lease of the last IP that was issued > and drop packets using it. For a single device being plugged in that > won't have any impact, and if for some reason you buy a new router and > plug it in you don't have to worry about your old router still having > a lease. This is less standards-compliant, but perhaps more > clueless-friendly. > > In general, though, you really shouldn't be plugging your ISP's modem > into anything but a router for general use. In fact, I have the > router provided by my ISP configured as a bridge and running into > another router (FIOS uses MoCA over coax in the standard install and > I'm too lazy to run CatV and beg Verizon to reconfigure the modem to > use the RJ45 connection instead). Note that if you use an > ISP-provided router there is a good chance that they can essentially > VPN into your LAN. The last time I called up Verizon over a cablecard > issue they helpfully turned on DHCP on my router so that it started > competing with my DHCP server, and then I was wondering why PXE was > randomly failing. Now all they can do is disable bridge mode, which > will break my external connection and be a fairly obvious point to > troubleshoot. Right, thanks for the explanation :) . Thankfully, our ISP only gave us the modem (though they also offer modems with WLAN for 5€ a monthg :-/ ). The router we bought off eBay ourselves :) . -- Marc Joliet -- "People who think they know everything really annoy those of us who know we don't" - Bjarne Stroustrup
signature.asc
Description: PGP signature
