Russel => "Having to modify the client device means you have already failed. It is supposed to be "just works"."
"DHCP is built on a client-server model. DHCP allows but does not require the configuration of client parameters not directly related to the IP protocol." http://www.ietf.org/rfc/rfc2131.txt Russel => "The Zhone/Paradyne DSL modems that Integra deploys are in the latter category. In fact, by default, they hand out leases over the entire available address range (.2 through .254 in a /24). Russel => *They don't bother to check whether the IP address is in use (e.g. by pinging) before hand.* This makes trying to use static IPs on these networks highly problematic" -- This behavior is not defined in the RFC. "The client SHOULD perform a final check on the parameters (e.g., ARP for allocated network address), and notes the duration of the lease specified in the DHCPACK message. At this point, the client is configured. If the client detects that the address is already in use (e.g., through the use of ARP), the client MUST send a DHCPDECLINE message to the server and restarts the configuration process." "In "manual allocation", a client's IP address is assigned by the network administrator, and DHCP is used simply to convey the assigned address to the client." -- In other words the Network Administrator is responsible for either specifying specific ip addrs for specific hosts or carving out a pool of ip addresses that will be manually configured and not include them in the DHCP dynamically assigned ip address pool. -- In summary, I realize that many of the consumer market products don't implement the DHCP RFC completely or that some ISPs may change the features and functions as they see fit. I just want to be clear where the problem lies, which is not with DHCP itself as much as the lack of understanding of how it works, how it's configured and how it may or may not be implemented by a hardware vendor or ISP. On Thu, Aug 15, 2013 at 12:00 PM, <[email protected]> wrote: > Send PLUG mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > http://lists.pdxlinux.org/mailman/listinfo/plug > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of PLUG digest..." > > > Today's Topics: > > 1. Re: Belkin N900 Not Seen at 192.168.2.1 => Russel S. > (Russell Senior) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Wed, 14 Aug 2013 17:47:42 -0700 > From: Russell Senior <[email protected]> > Subject: Re: [PLUG] Belkin N900 Not Seen at 192.168.2.1 => Russel S. > To: Portland Linux/Unix Group <[email protected]> > Message-ID: <[email protected]> > Content-Type: text/plain; charset=us-ascii > > >>>>> "Mike" == Mike C <[email protected]> writes: > > Russell> Not such a good idea, IMHO. The "access point" dhcp server > Russell> is going to be giving itself out as the default route, unless > Russell> you can tell it otherwise. > > [...] > > Mike> With that being said, the standard issue dhcleint,conf file > Mike> would request routers from the DHCP server and would need to > Mike> modified. > > Having to modify the client device means you have already failed. It > is supposed to be "just works". > > Russell> Also, some embedded dhcp servers listen for other dhcp > Russell> servers on the network before starting. If they hear one, > Russell> they'll disable themselves. Others, stomp right ahead > Russell> blindly. > > Mike> I've been working with computer networks for 15 yrs and I have > Mike> yet to see this behavior. > > Let me tell you, I have. And I'd be happy to introduce you to them. > > I wouldn't swear to it, but I think dnsmasq might do the former out of > the box. In any case, I know for certain I have seen this behavior > multiple times, enough to learn to watch out for it. Looking back > through my notes, it might have been seen with a stock WRT54G and > another device with OpenWrt dnsmasq. > > The Zhone/Paradyne DSL modems that Integra deploys are in the latter > category. In fact, by default, they hand out leases over the entire > available address range (.2 through .254 in a /24). They don't bother > to check whether the IP address is in use (e.g. by pinging) before > hand. This makes trying to use static IPs on these networks highly > problematic. It is just a matter of time before the helpful DHCP > server cheerfully stomps on your carefully chosen IPaddr. Just as a > capper, Integra refuses to provide a login to let you configure the > DSL modem yourself. Which means, every trivial little change you > might want to make requires a support call. > > > -- > Russell Senior, President > [email protected] > > > ------------------------------ > > _______________________________________________ > PLUG mailing list > [email protected] > http://lists.pdxlinux.org/mailman/listinfo/plug > > > End of PLUG Digest, Vol 107, Issue 26 > ************************************* > _______________________________________________ PLUG mailing list [email protected] http://lists.pdxlinux.org/mailman/listinfo/plug
