pjw@usna.navy.mil, , jw@math30, (Peter J. Welcher (math FACULTY)) (05/29/91)
Laptop PC's and Unix boxes will be upon all us administrators soon. Complete with Ethernet interfaces. My question: how do you assign Internet addresses to people who may plug into different subnets on different days ? If you give them multiple addresses you could eat up a lot of address space in a hurry ? This is going to become a potential hassle in the next year or two. How are people going to deal with it ? Our case: we have classrooms on a different subnet than faculty offices. Laptop PC's in the offing. Sun servers on both subnets. How do I deal with 100+ PC's that could be on either of my two subnets ? How about 4000 PC's plugging into any of the 30-50 subnets in the school ?
ketell@mercury (Gregory Ketell) (05/29/91)
> Date: Tue, 28 May 91 14:16:40 EDT > From: "Peter J. Welcher (math FACULTY" <pjw@usna.navy.mil>, jw@math30, > ")"@BRL.MIL > Laptop PC's and Unix boxes will be upon all us administrators soon. > Complete with Ethernet interfaces. My question: how do you assign > Internet addresses to people who may plug into different subnets on > different days ? If you give them multiple addresses you could eat up > a lot of address space in a hurry ? > This is going to become a potential hassle in the next year or two. > How are people going to deal with it ? I may catch a lot of flak from the Gurus but here is my view: Why bother giving them multiple addresses at all. Give each machine a single address, whatever network they hook up to they will still be reachable. (ex. You can reach me, I can reach you but we are not only on different subnetworks but across the nation.). Just assign each machine the IP address for their "Home Connection", ie if they are in your math subnetwork just assign them an address on that subnet. When they hook up to another net they will operate on that net with their own address. Admittedly this will only work as long as both subnets can reach each other. Greg Ketell Networks Administrator Computing Services Cal. State Univ., Hayward ketell@pyr.csuhayward.edu
hubcap@hubcap.clemson.edu (System Janitor) (05/29/91)
Hmmm... what if you gave the IP addresses to the taps. You know, ``whoever plugs in here is 123.45.678.9''. Of course, they'd have to edit their telnet.config file (or whatever) before they hooked up everytime they sat down at a new place, but if they want to be able to plug in everywhere, that shouldn't be too much to ask. On the other hand, (I've never thought about it before) the thought of a dynamic physical network topology run by the whim of the users sounds kind of scary to me. -Mike
mouse@thunder.mcrcim.mcgill.edu (der Mouse) (05/30/91)
In article <27035@adm.brl.mil>, ketell@mercury (Gregory Ketell) writes: >> Laptop PC's and Unix boxes will be upon all us administrators soon. >> Complete with Ethernet interfaces. My question: how do you assign >> Internet addresses to people who may plug into different subnets on >> different days ? If you give them multiple addresses you could eat >> up a lot of address space in a hurry ? > I may catch a lot of flak from the Gurus but here is my view: > Why bother giving them multiple addresses at all. Give each machine > a single address, whatever network they hook up to they will still be > reachable. (ex. You can reach me, I can reach you but we are not > only on different subnetworks but across the nation.). Only because the routing algorithms take advantage of the fact that at each level of subnetting, all the way from the network number down to the smallest subnet, each network is fully connected within itself. Your proposal breaks this. > Just assign each machine the IP address for their "Home Connection", > ie if they are in your math subnetwork just assign them an address on > that subnet. When they hook up to another net they will operate on > that net with their own address. > Admittedly this will only work as long as both subnets can reach each > other. It will also be a major nightmare for the routing protocols. RIP, which I would guess is the commonest routing protocol within small (campus-sized) networks, cannot deal with this. Most UNIX boxes will be unable to reach the machine when not on its home subnet, unless they are told that the network isn't subnetted at all and then the gateways made to do proxy arp - which opens up a whole 'nother can of worms. No, I don't have any good solution either. We fortunately have not had to deal with the problem yet. der Mouse old: mcgill-vision!mouse new: mouse@larry.mcrcim.mcgill.edu
medin@cincsac.arc.nasa.gov (Milo S. Medin) (05/31/91)
In article <1991May30.084135.25587@thunder.mcrcim.mcgill.edu>, mouse@thunder.mcrcim.mcgill.edu (der Mouse) writes: |> In article <27035@adm.brl.mil>, ketell@mercury (Gregory Ketell) writes: . . . |> |> > Why bother giving them multiple addresses at all. Give each machine |> > a single address, whatever network they hook up to they will still be |> > reachable. (ex. You can reach me, I can reach you but we are not |> > only on different subnetworks but across the nation.). |> |> Only because the routing algorithms take advantage of the fact that at |> each level of subnetting, all the way from the network number down to |> the smallest subnet, each network is fully connected within itself. |> Your proposal breaks this. |> Not quite. OSPF was designed with variable length subnet in mind. There is no notion of class A, B, or C nets in OSPF. Every net is passed with a mask. Note this also obviates the need to have subnetted nets be contiguous. You can have pieces of a class B connected via a Class C in the middle. This works fine. Since EGP and BGP do not pass subnet info around, this functionality is limited to the insides of an OSPF system, but that's still very useful. All vendors shipping OSPF implementations support this kind of variable length mask support. So, you should be able to pull this off. |> > Just assign each machine the IP address for their "Home Connection", |> > ie if they are in your math subnetwork just assign them an address on |> > that subnet. When they hook up to another net they will operate on |> > that net with their own address. |> |> > Admittedly this will only work as long as both subnets can reach each |> > other. |> |> It will also be a major nightmare for the routing protocols. RIP, |> which I would guess is the commonest routing protocol within small |> (campus-sized) networks, cannot deal with this. Most UNIX boxes will |> be unable to reach the machine when not on its home subnet, unless they |> are told that the network isn't subnetted at all and then the gateways |> made to do proxy arp - which opens up a whole 'nother can of worms. |> As I said, OSPF does not have this problem. I expect RIP use to gradually fade away until it's just used as an easy way for hosts to find routers, (ie all routers just send RIP default) and not for much else. In fact, if you really take advantage of this, you could pull a laptop off the LAN interface, and have it keep it's address when it dials into a router via SLIP or PPP. When on the LAN, the "most specific route" points to the LAN itself, and everything is as it works now. When dialing into a terminal server acting as a router and speaking OSPF, the server orginates a host route to the target address. The host route is more specific and thus the network routes that way instead of to the LAN (for just that host). The router attached to the LAN can proxy-arp so hosts on the LAN can talk to the remote laptop. All of this is doable with OSPF. Now, you just need to have your terminal servers run OSPF (since a well known vendor's server is built on top of BSD Unix, and since gated will shortly support OSPF, this isn't as far fetched as it may sound), and viola! The IETF actually does do good work from time to time. OSPF is a draft internet standard right now, and hopefully will go to full standard (like SNMP) in 6-9 months. Ask for it by name, accept no substitutes! I'm a little bit biased here, since I worked on the design of OSPF, but I think it will handle the case you are thinking about. Thanks, Milo PS Usual disclaimers apply...
jeff@crash.cts.com (Jeff Makey) (06/01/91)
It seems to me that there is no existing standard protocol for dynamic
assignment of internet addresses to domain names. It would solve the
problem nicely. At work, our Macintoshes use MacTCP and a Gatorbox to
connect to our local internet, and when each Mac starts up its TCP/IP
software it is assigned an IP address by the Gatorbox. To work in
general on the Real Internet, this address assignment would have to be
integrated into the DNS.
:: Jeff Makey
Department of Tautological Pleonasms and Superfluous Redundancies Department
Posting from my temporary home at ...
Domain: jeff@crash.cts.com UUCP: nosc!crash!jeff