Reverse or inverse ARP from windows/linux - no way (!?!?)
in [Design]
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From: glen herrmannsfeldt on 26 Mar 2010 16:01 In comp.protocols.tcp-ip Didi <dp(a)tgi-sci.com> wrote: (snip) > In an attempt to solve it I spent 10 minutes adding RARP reply > to our device Ethernet related stuff - so it would reply to an ARP > inquiry #3 by sending its IP address (it only has one); and then spent > perhaps 3 hours googling, moogling, you name it, searching for some > piece of code to do that at the wintel side. Even rebooted the wintel > laptop to ubuntu to try it out from there (thought arp -r or something > would just work), oh no. No way. Spent perhaps half an hour of > moogling for linux rarp, same thing. Yesterday, not long after reading this, I was reading about a device that offers RARP, ARP, BOOTP, and DHCP as ways of assigning it an IP address. Looking at the list, I didn't see how they would do it with ARP, but... (This was suggested for Windows 98.) arp -s (desired IP address) (device MAC address) ping (desired IP address) The device is designed such that when no IP address is assigned that it looks for such ICMP packets. They could only arrive from hosts configured with such static ARP entries. Once an address is assigned (this way, or any other) the device ignores such. That avoids the problem of no RARP, BOOTP, or DHCP on W98. -- glen
From: David Schwartz on 26 Mar 2010 16:12 On Mar 26, 11:25 am, "markp" <map.nos...(a)f2s.com> wrote: > That is what I was going to suggest. Just regularly send your aquired > address via a UDP broadcast packet (say once a second), the bandwidth that > would use is very low. Please don't do that. Instead, listen on a UDP broadcast port for a UDP broadcast query. You can reply to that query either broadcast or unicast (just to the querier). DS
From: markp on 26 Mar 2010 18:52 "David Schwartz" <davids(a)webmaster.com> wrote in message news:ec062dee-e5d8-49f2-8ca1-7cd02a7b54e7(a)u15g2000prd.googlegroups.com... On Mar 26, 11:25 am, "markp" <map.nos...(a)f2s.com> wrote: >> That is what I was going to suggest. Just regularly send your aquired >> address via a UDP broadcast packet (say once a second), the bandwidth >> that >> would use is very low. > Please don't do that. Instead, listen on a UDP broadcast port for a > UDP broadcast query. You can reply to that query either broadcast or > unicast (just to the querier). > DS Of course, had a bit of a mind freeze there. That's a much more sensible way of doing it. You still have the question of how often to update the info because the DHCP server could potentially re-allocate addresses, but with your enquiry approach an update could be done on demand when needed. Mark.
From: Barry Margolin on 26 Mar 2010 21:36 In article <4BAC2BE3.FAC92EF2(a)Hovnanian.com>, "Paul Hovnanian P.E." <Paul(a)Hovnanian.com> wrote: > Didi wrote: > > > > I tried today to figure out a simple way to give users of our > > new netmca ( http://tgi-sci.com/tgi/nmcatb.htm ) to locate its > > IP address once it gets one via dhcp when there is no internet > > at the moment (when there is the device posts its IP to our domain > > and customers can see it using a browser). > > > > > Here's an idea: http://en.wikipedia.org/wiki/Dynamic_DNS > > That will solve the dynamic (DHCP assigned) IP address to a DNS entry > that the world can resolve. Isn't that what he's referring to in the parentheses? He's trying to find a way to do it when there's no DNS server to update. -- Barry Margolin, barmar(a)alum.mit.edu Arlington, MA *** PLEASE post questions in newsgroups, not directly to me *** *** PLEASE don't copy me on replies, I'll read them in the group ***
From: Didi on 28 Mar 2010 20:33
On Mar 26, 12:54 am, Didi <d...(a)tgi-sci.com> wrote: > I tried today to figure out a simple way to give users of our > new netmca (http://tgi-sci.com/tgi/nmcatb.htm) to locate its > IP address once it gets one via dhcp when there is no internet > at the moment (when there is the device posts its IP to our domain > and customers can see it using a browser). > > Turned out there is nothing like an easy way to do that! > > There are some utilities which can be used to ping the entire subnet; > then list the arp cache, locate the known MAC address and > see its IP. But these are far from something one would want to ask > customers to deal with, long lists, necessity to search etc. , heck, > it > will generate more calls to me than if I do it for them every time. > > In an attempt to solve it I spent 10 minutes adding RARP reply > to our device Ethernet related stuff - so it would reply to an ARP > inquiry #3 by sending its IP address (it only has one); and then spent > perhaps 3 hours googling, moogling, you name it, searching for some > piece of code to do that at the wintel side. Even rebooted the wintel > laptop to ubuntu to try it out from there (thought arp -r or something > would just work), oh no. No way. Spent perhaps half an hour of > moogling for linux rarp, same thing. I think I got to the bottom of it - why this is impossible under windows, that is. I had posted the same question in a local (Bulgarian) forum, and today a guy replied and posted this pointer: http://en.wikipedia.org/wiki/Raw_socket Turns out this is just not doable under windows without defeating the system somehow... hence no such utility. He says he needed the same thing and wrote himself a GNU/Linux utility so apparently it is doable there; but I have not located such a utility in my half hours search (nor do I need it particularly, most if not all customers run windows and if someone is running linux chances are he will figure something out without my assistance. Here is the topic in the forum (Bulgarian/Cyrillic, most of you will see just funny characters :-) ): http://mcu-bg.com/mcu_site/viewtopic.php?t=7680 Dimiter ------------------------------------------------------ Dimiter Popoff Transgalactic Instruments http://www.tgi-sci.com ------------------------------------------------------ http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/ > > How on Earth is that possible?! I can understand how many things > are retarded as one would expect them to be on a x86 based thing, > but this is too simple even for the x86 world. > > Any ideas? I have not faced the issue in real life yet (users tend > to have internet) but this is bound to happen and I am looking for > some solution. > > Dimiter > > ------------------------------------------------------ > Dimiter Popoff Transgalactic Instruments > > http://www.tgi-sci.com > ------------------------------------------------------http://www.flickr.com/photos/didi_tgi/sets/72157600228621276/ |