Path: utzoo!attcan!uunet!convex!killer!osu-cis!tut.cis.ohio-state.edu!mailrus!iuvax!purdue!decwrl!labrea!Portia!Jessica!morgan From: morgan@Jessica.stanford.edu (RL "Bob" Morgan) Newsgroups: comp.protocols.tcp-ip Subject: Re: Dynamic IP address assignment Message-ID: <4209@Portia.Stanford.EDU> Date: 23 Nov 88 22:41:41 GMT References: <1378@aucs.UUCP> <26200@bu-cs.BU.EDU> Sender: news@Portia.Stanford.EDU Reply-To: morgan@Jessica.stanford.edu (RL "Bob" Morgan) Organization: Stanford University Lines: 28 Kent England replies: > In article lear@NET.BIO.NET > (Eliot Lear) writes: > > >Wouldn't you run into a problem with ARP caches if you dynamically > >assign internet addresses to ethernet based machines? > > Age the arp cache. Then set a "re-use" timer on the IP > address to be, say 3x, the arp cache time-out. > Of course, how do you know when an IP address is released? > There oughta be a protocol. Some people have allowed as how a broadcast ARP Reply containing an IP-address/Ethernet-address mapping will cause "most" hosts that hear it to enter the info into their ARP cache. This would allow a new assignment to be "set", presumably after confirming with ARP Requests that the previous assignment had been released. (It would also allow a nasty program to thoroughly mess with everybody's ARP caches, but we've had enough of nasty programs for the moment, I think.) So the question is, "most", or "all"? Does the ever-forthcoming Host Requirements RFC make reference to this behavior? - RL "Bob" Morgan Networking Systems Stanford